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ArticleApril 25, 2013

Mechanism and Selectivity of Rhodium-Catalyzed 1:2 Coupling of Aldehydes and Allenes
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Journal of the American Chemical Society

Cite this: J. Am. Chem. Soc. 2013, 135, 20, 7647–7659

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https://doi.org/10.1021/ja4014166

Published April 25, 2013

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Abstract

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The rhodium-catalyzed highly regioselective 1:2 coupling of aldehydes and allenes was investigated by means of density functional theory calculations. Full free energy profiles were calculated, and several possible reaction pathways were evaluated. It is shown that the energetically most plausible catalytic cycle is initiated by oxidative coupling of the two allenes, which was found to be the rate-determining step of the overall reaction. Importantly, Rh–allyl complexes that are able to adopt both η³ and η¹ configurations were identified as key intermediates present throughout the catalytic cycle with profound implications for the selectivity of the reaction. The calculations reproduced and rationalized the experimentally observed selectivities and provided an explanation for the remarkable alteration in the product distribution when the catalyst precursor is changed from [RhCl(nbd)]₂ (nbd = norbornadiene) to complexes containing noncoordinating counterions ([Rh(cod)₂X]; X = OTf, BF₄, PF₆; cod = 1,5-cyclooctadiene). It turns out that the overall selectivity of the reaction is controlled by a combination of the inherent selectivities of several of the elementary steps and that both the mechanism and the nature of the selectivity-determining steps change when the catalyst is changed.

Subjects

1 Introduction

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Rhodium(I) complexes are well-established catalysts for three-component cycloadditions of unsaturated compounds, yielding carbocycles with various ring sizes (e.g., six-membered; Scheme 1a). (1) Rhodium(I) also catalyzes hydroacylation reactions in which an acyl unit and the hydrogen atom of an aldehyde are added across a C–C multiple bond (Scheme 1b). (2) A reductive version of the latter process, furnishing the corresponding alcohols, has also been developed (Scheme 1c). (3) In 2006, Krische and co-workers reported a novel reaction that can be considered as a crossover between those presented in Scheme 1a and Scheme 1c. In its course, two molecules of acetylene are coupled with one molecule of aldehyde under a hydrogen atmosphere to form a linear allylic alcohol product (Scheme 2a). (4, 5) Very recently, a combination of the in principle more fundamental couplings from Scheme 1a,b has also been successfully accomplished. (6, 7) In particular, a significant example comes from the laboratory of Murakami and consists of a 1:2 coupling of aldehydes and allenes (Scheme 2b). (6)

The reaction in Scheme 2b indeed constitutes a state-of-the-art method in synthetic organic chemistry. It is inherently atom-economical and leads to a large increase in molecular complexity in a single step. A particularly appealing feature of this process is its selectivity, which is a much more complex issue than in the reaction involving acetylene (Scheme 2a). Considering only the couplings of two monosubstituted allene moieties of type 2 with one molecule of aldehyde 1, 36 different isomers of the product are possible, with various connectivities and Z/E arrangements of the double bonds. (8) Experimentally, when [RhCl(nbd)]₂ (nbd = norbornadiene) was used as the rhodium source and 1,2-bis(diphenylphosphino)ethane (dppe) as the ligand, product 3 was obtained with 91% selectivity, accompanied by two minor isomers, 4 (6%) and 5 (3%). (6) Very interestingly, when the chloride was replaced by a noncoordinating counterion such as TfO^–, BF₄^–, or PF₆^–, the selectivity of the reaction was switched, and compound 5 became the dominant product (87–95%). (6) The common features of the products obtained under the two sets of reaction conditions are that the two allene moieties are coupled through their central atoms (C2–C2 linkage) and the aldehyde is attached to one of the terminal carbons (C1 or C3) of one of the allenes.

The reaction mechanism of the related three-component reductive coupling shown in Scheme 2a has been investigated by a combination of experimental and computational approaches. (9) It was established the reaction takes place via an initial oxidative coupling of two acetylene molecules followed by migratory insertion of the aldehyde molecule, hydrogenolysis, and reductive elimination. (9) Hence, except for the extra hydrogenolysis step, this mechanism is similar to the well-established catalytic cycle of the trimerization process depicted in Scheme 1a. (1d)

In the case of the 2:1 coupling of allenes and aldehydes (Scheme 2b), it is not evident that an analogous mechanistic pathway is followed. It has been shown experimentally that allenes of type 2 indeed undergo an initial oxidative coupling in the presence of a Rh(I) catalyst, but instead of the subsequent migratory insertion that would eventually result in the regular [2 + 2 + 2] cycloaddition (Scheme 1a), a β-hydride elimination/reductive elimination sequence occurs, leading overall to a linear dimer. (10, 11) Additionally, it is known that the hydroacylation reactions (Scheme 1b) are initiated by oxidative addition of aldehydes to Rh(I) complexes, (2a) so this process may also be involved in the mechanism of the combined reaction shown in Scheme 2b. Finally, there is also an additional possibility of an initial oxidative coupling between the aldehyde and the allene moieties that has been shown to take place in some catalytic cycles. (12) A mechanism starting with the oxidative coupling of aldehyde and allene was actually suggested by Murakami and co-workers in their report. (6)

These possible mechanisms for the reaction, suggested by the experimental findings or proposed in the literature, are summarized in Scheme 3. They differ in regard to the initial step, which is either C–H oxidative addition, allene–allene oxidative coupling, or aldehyde–allene oxidative coupling. In addition to the general mechanism, there is the issue of the reaction selectivity and its sources. Each of the pathways shown in Scheme 3 may yield each of the 36 possible product isomers, including the experimentally observed 3, 4, and 5, by simply altering the positions at which the new bonds are formed. Moreover, all three pathways are consistent with the results of deuterium labeling studies carried out experimentally. (6) In addition, for almost all of the intermediates in Scheme 3 one can envision alternative reactions that they may undergo (not shown in the scheme) leading to side products with entirely different structures (e.g., 1–2 or 2–2 dimers, etc.), which adds to the complexity of the system.

Scheme 3. Possible General Mechanistic Pathways for the Reaction in Scheme 2b, As Suggested by Experimental Findings or Proposed in the Literature^a

Considering the significance of the coupling reaction depicted in Scheme 2b and the current poor understanding of its mechanism, in particular the origins of the observed selectivity, we decided to investigate it computationally by means of density functional theory (DFT). The calculations showed that the reaction indeed initially follows the pathway starting with oxidative coupling of two allene molecules (Scheme 3, path B). However, we found that a not previously suggested allylation of the aldehyde takes place subsequently with important selectivity implications. It is shown that a key role in the reaction mechanism is played by rhodium complexes containing allyl ligands that can adopt either η³ or η¹ coordination, which display intrinsically distinct reactivities. Moreover, it is demonstrated that the reaction catalyzed by rhodium complexes with noncoordinating counterions follows a partially different mechanistic route involving an alkoxide oxidation step. The calculations provide an explanation for the observed selectivity switch when the counterion in the Rh catalyst is altered.

2 Computational Details

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All of the calculations were performed using the Gaussian 03 package (13) and the B3LYP functional. (14) Geometry optimizations were done with a combined basis set in which the LANL2DZ basis set with pseudopotential (15) was used for Rh and the 6-31G(d,p) basis set was used for all other atoms. Frequencies were computed analytically at the same level of theory to confirm whether the structures were minima (no imaginary frequencies) or transition states (only one imaginary frequency). Selected transition-state structures were confirmed to connect the correct reactants and products by intrinsic reaction coordinate (IRC) calculations. To obtain better accuracy of the final energy values, the energies of the optimized geometries were recalculated using single-point calculations with a larger basis set, namely, LANL2DZ for Rh and 6-311+G(2d,2p) for the other atoms. The effect of solvation was evaluated by performing single-point self-consistent reaction field calculations with the conductor-like polarizable continuum model (C-PCM) (16) as implemented in Gaussian 03. The parameters for toluene (ε = 2.379), corresponding to the experimental conditions, and the united atom (UA0) radii were used in these calculations.

The final Gibbs energies reported in the article (ΔG_Tol) are the large-basis-set single-point energies with Gibbs energy corrections (at 298.15 K), solvation corrections, and corrections for dispersion effects using the method of Grimme. (17) Inclusion of the dispersion effects has recently been shown to improve the performance of the B3LYP method significantly. (18)

The calculations were carried out using the full structure of the dppe ligand, while the aldehyde and allene reactants were represented with smaller model structures, namely, benzaldehyde (1, R¹ = Ph in Scheme 2b) and buta-1,2-diene (2, R² = Me), respectively.

3 Results and Discussion

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Because of the number of possible mechanistic pathways (Scheme 3), the reaction poses a considerable challenge from a computational point of view. In this section, we first focus on the [RhCl(dppe)]-catalyzed reaction, assuming that chloride is coordinated to the metal center. The mechanism of the reaction is systematically examined step by step by evaluating all of the possible pathways, including potential side reactions. After the overall mechanism is established, the full catalytic cycle and the energy profile are summarized and the origins of the regioselectivity are discussed. In the final part, we present the results of the calculations on the reaction catalyzed by the cationic [Rh(dppe)]⁺ complex, which is the putative active species in the reactions using catalyst precursors containing noncoordinating counterions. The obtained free energy profile is then analyzed, and the origins of the observed alteration of the selectivity when the catalyst is changed are explained.

All of the free energies are reported relative to the sum of the free energies of the free reactants and catalyst (i.e., 1 + 2 × 2 + [Rh], where [Rh] = [RhCl(dppe)] or [Rh(dppe)]⁺), which we have chosen to set equal to zero.

3.1 Initial Step of the Catalytic Cycle: Oxidative Coupling versus Oxidative Addition

Before considering the various reaction pathways, we evaluated the different modes of binding between the catalyst and the reactants. The calculations showed that coordination of allene 2 to the Rh catalyst to give INT1 is exergonic by 8.9 kcal/mol, whereas binding of aldehyde 1 to form INT1a is exergonic by 1.6 kcal/mol (Figure 1). The introduction of any additional ligands always resulted in an increase in the free energy, which is in agreement with the known preference of d⁸ metal complexes to adopt a four-coordinate square-planar geometry (see the Supporting Information). Hence, INT1 containing a single allene molecule, dppe, and chloride as ligands (see Figure 2 for the structure) is the lowest-energy Rh(I) species, to which the barriers for the initial step should be related.

Figure 1. Free energy profiles for the possible initial steps of the reaction. The intermediates connecting **INT1** with **TS1** and **TS1b** were found to be higher in free energy than **INT1**, so they are not shown in the diagram (see the Supporting Information for details).

Figure 2. Optimized structures of selected intermediates and transition states for the initial step (distances in Å and angles in deg). For clarity, the phenyl substituents on the phosphorus centers have been omitted in the figure.

As shown in Scheme 3, three general mechanistic pathways for the investigated reaction are possible, each of which begins with a different step, namely, C–H oxidative addition (path A), allene–allene oxidative coupling (path B), or aldehyde–allene oxidative coupling (path C). We optimized the transition states (TSs) corresponding to these steps and compared them in terms of their relative free energies, taking into account all of the possible coupling patterns of the reactants where applicable.

The C–H oxidative addition of aldehyde (path A in Scheme 3) was found to take place via transition state TS1a (Figure 2). It requires overcoming an overall barrier of 25.2 kcal/mol relative to INT1 and involves an initial interconversion into the aldehyde-containing complex INT1a (Figure 1). The oxidative addition results in the formation of the Rh(III) hydride INT2a, and the process is endergonic by as much as 22.9 kcal/mol.

The oxidative coupling of two allene moieties (path B in Scheme 3) was much more complicated to investigate than the oxidative addition. In the course of this step, the C–C bond formation may occur between any of the three carbon atoms of each of the coupling partners (C1–C1, C1–C2, C1–C3, C2–C1, etc.). Additionally, when the central atom of the allene (C2) is engaged in the C–C bond formation, extra combinations arise from the fact that either of the terminal carbons (C1 or C3) may bind to the rhodium center. When the Z/E arrangements of the double bonds and, in three cases, the cis/trans isomers are also taken into account, there are in total 24 distinct TSs that must be considered (Scheme 4). The free energies for all of these were calculated, and the one with the lowest free energy was found to be TS1, whose structure is shown in Figure 2 (structures and energies of all of the TSs are given in Supporting Information). In this TS, the rhodium center, which constitutes the largest steric bulk in the system because of the proximity of the phenyl-substituted phosphine ligand, is coordinated to the least-substituted carbons (C1) of the allenes. Additionally, the Z,Z arrangement of the double bonds minimizes the repulsion in the other part of the structure. The free energy of TS1 was calculated to be 21.5 kcal/mol higher than that of INT1 (Figure 1). The free energies of the other TSs shown in Scheme 4 were calculated to be higher than that of TS1 by at least 2.2 kcal/mol (see the Supporting Information).

Scheme 4. Possible Transition States for Oxidative Coupling of the Two Allene Moieties^a

Interestingly, TS1 does not lead to the expected five-membered metallacycle but instead yields an octahedral Rh(III) complex INT2, containing an η³-allyl-η¹-allyl ligand (see Figure 2 for the structure). (19) In what follows, we will refer to this kind of intermediate as η³,η¹-bis(allylic), in accordance with the literature. (20) The formation of INT2 is exergonic by 19.6 kcal/mol relative to INT1. This kind of η³,η¹-bis(allylic) ligand could be expected to undergo syn/anti isomerization of the methyl substituents. However, intermediate INT2 possesses some unique features that result in the preservation of its stereochemical configuration as formed in the course of the reaction from TS1 (i.e., Z double-bond geometry and anti CH₃ group in the η³-allyl system). First, the methyl substituent in the η³-allyl of INT2 cannot move from the anti position to the syn position via an η³–η¹–η³ isomerization mechanism, as the required rotation in the transient η¹ complex is impossible because the allylic system is a part of metallacycle. Second, it is possible for the η³ and η¹ allyl groups in INT2 to exchange places, but this also maintains the overall configuration. During such a process, the anti CH₃ group becomes a substituent of the Z-configured double bond and vice versa. Finally, INT2 may transiently be transformed into an isomeric η³,η¹-bis(allylic) complex, INT2′, that is calculated to be 8.5 kcal/mol higher in free energy than INT2 (Scheme 5). However, such an interconversion also leaves the stereochemical arrangement of the allene dimer moiety intact. These properties are of importance for the overall selectivity of the reaction, as will be discussed below.

Scheme 5. Possible η³–η¹–η³ Isomerization of **INT2**^a

As a final option for the initial step, oxidative coupling between the aldehyde and allene molecules was also examined (path C in Scheme 3). Similar to the case of allene–allene oxidative coupling, the C–C bond may be formed between the carbonyl carbon and positions C1, C2, or C3 of the allene. When the Rh coordination as well as the Z/E and cis/trans isomers are also considered, there are seven possible transition states (see the Supporting Information). The one with the lowest free energy among them is TS1b (Figure 2). The corresponding free energy barrier is 29.7 kcal/mol from INT1, and the formation of the resulting Rh(III) complex INT2b is endergonic by 8.7 kcal/mol relative to INT1 (Figure 1).

These results clearly point to oxidative coupling of the two allenes leading to intermediate INT2 as the favored initial step of the mechanism. The transition state for the C–H oxidative addition (TS1a) is 3.7 kcal/mol higher than TS1 (but lower than many of the transition states depicted in Scheme 4). On the other hand, the oxidative coupling between the aldehyde and allene was found to occur via high-energy transition states, the lowest of which (TS1b) is 8.2 kcal/mol higher than TS1. Importantly, the formation of INT2 is irreversible, and therefore, already at this point it is possible to dismiss paths A and C of Scheme 3 as plausible reaction mechanisms. Using the same argument, one can also discard all of the pathways starting with oxidative coupling of the two allenes in arrangements other than in TS1 (Scheme 4). Hence, from the reaction mixture containing the Rh(I) catalyst (cat), aldehyde 1, and allene 2, intermediate INT2 should be formed practically exclusively. As explained above, this intermediate has a defined stereochemical configuration that strongly narrows the number of possible final products of the reaction. In the following sections, we will show that the experimentally observed product 3, as well as the minor side products 4 and 5, can all be derived from INT2 as a common precursor.

3.2 Formation of the Second C–C Bond

Once the two allene molecules are coupled in the first step of the mechanism to form INT2, the second C–C bond formation must take place, incorporating the aldehyde moiety into the structure and thus assembling the complete backbone of the product. It has been suggested that the second C–C bond formation should occur via migratory insertion of the aldehyde into the Rh–C bond. (6) Such a course of the reaction was also established in mechanistic studies on the above-mentioned related reductive 2:1 coupling of acetylenes with aldehydes (Scheme 2a). (9) In addition to insertion of the aldehyde, INT2 may potentially undergo a competing process, namely, a β-hydride elimination that would eventually lead to the formation of the dimer of allene 2. There is experimental evidence that the latter pathway is followed in the absence of aldehyde 1 in the reaction mixture. (10) In the present study, we discovered an additional alternative for the C–C bond formation that has not been proposed previously and that turns out to have a much lower barrier than the two other processes. This alternative pathway involves direct allylrhodium addition to the aldehyde. In this section, these mechanistic possibilities are investigated and compared. (21)

Irrespective of the specific way the new C–C bond is formed, the reaction begins with the coordination of aldehyde 1 to the rhodium center. To create the necessary coordination site for the aldehyde, the allyl ligand must change its binding mode from η³ to η¹. This may occur in two distinct ways, with either C1 or C3 ligating the metal center in the resulting complex (INT3 or INT3′, respectively; Figure 3). This transformation was calculated to be endergonic by 4.1 and 6.7 kcal/mol, respectively.

Figure 3. Free energy profile for the formation of the second C–C bond.

From INT3, the migratory insertion may occur only at the C1 position because of the symmetric structure of this intermediate, while on the other hand, insertion in INT3′ can take place at either C1 or C3. The calculations showed that the lowest-energy transition state leads to the insertion at C1 (TS-INS) and arises from INT3. The second-lowest transition state found was TS-INS′, which involves the insertion at C3 from INT3′. The corresponding barriers for TS-INS and TS-INS′ relative to INT2 are 29.8 and 31.7 kcal/mol, respectively (Figure 3). The free energy difference between them can be explained by the steric repulsion between the proximal methyl group and the aldehyde in the latter transition state.

The alternative C–C bond formation pathway that we discovered to be possible starting from INT3 or INT3′ is a direct attack of the σ-allyl ligand on the aldehyde coordinated to the rhodium center. (22) Such a reaction, which occurs via a six-membered cyclic transition state (TS2 or TS2′, respectively; see Figure 3 for schematic illustrations and Figure 4 for optimized structures), was found to be energetically more favorable than the migratory insertion by as much as 15 kcal/mol.

Figure 4. Optimized structures of the allylation reactants, transition states, and resulting complexes.

In this case, the C–C bond formation from INT3 can occur only at the C3 position (TS2). The corresponding barrier was calculated to be 14.7 kcal/mol relative to INT2. However, allylation from INT3′ may take place at either C1 or C3, but the former scenario is lower in free energy (TS2′ in Figure 3) and requires overcoming an overall barrier of 15.3 kcal/mol relative to INT2. In both TS2 and TS2′, the six-membered ring adopts the chairlike geometry (Figure 4) with the methyl and phenyl groups occupying the axial and equatorial positions, respectively. The small free energy difference between them might be explained by a steric repulsion between the methyl group and the Rh center in TS2′, which is not present in TS2. Transition states TS2 and TS2′ constitute the divergence point from which the reaction proceeds along two separate parallel pathways.

The allylations occurring via TS2 and TS2′ yield octahedral complexes INT4 and INT4′, respectively, containing η²-alkene and alkoxide ligands coordinated to Rh(III) (see Figure 4 for optimized structures). Interestingly, INT4 was found to be 0.9 kcal/mol less stable than INT4′.

Finally, the β-hydride elimination from INT2, the possible side reaction at this stage of the mechanism, was found to have a barrier of 33.0 kcal/mol relative to INT2 (via TS-H, whose optimized structure is given in the Supporting Information), which is 18.3 kcal/mol higher than that found for TS2 (Figure 3). Therefore, in the presence of aldehyde 1 in the reaction mixture, the allylation is expected to occur much more favorably, in agreement with the experimental results.

3.3 β-Hydride Elimination

The next step in the reaction pathway is the β-hydride elimination, which restores the carbonyl group (Scheme 3, path B). In both INT4 and INT4′, the only β-hydrogen available is the one originating from the aldehyde group, and hence, it will be exclusively transferred to the metal center. However, for the β-hydride elimination to take place, a vacant coordination site must be created to accommodate the hydride. This can be generated by dissociation of the η²-alkene from the metal center in INT4 and INT4′ followed by rotation of the alkoxide ligand. The calculations showed that this isomerization takes place through a series of steps, among which the highest-energy transition states are TS3 and TS3′ with barriers of 17.7 and 16.6 kcal/mol relative to INT4 and INT4′, respectively (Figure 5). A detailed description of the isomerization process, together with calculated free energy profiles and optimized structures, can be found in the Supporting Information.

Figure 5. Free energy profile for the β-hydride elimination step.

The isomerization results in intermediates INT5 and INT5′ containing an η³-allyl ligand, which were calculated to be higher in free energy by 6.8 and 4.7 kcal/mol relative to INT4 and INT4′, respectively. From INT5 and INT5′, the β-hydride elimination takes place with a simultaneous change in the coordination mode of the allyl group from η³ to η¹ in order to create a vacant site for the hydride at the metal center (TS4 and TS4′; see Figure 6 for optimized structures). The calculated free energies of TS4 and TS4′ relative to the respective intermediates INT5 and INT5′ are 9.0 and 10.1 kcal/mol (Figure 5), respectively. It should be noted that transitions states TS4 and TS4′ are lower in free energy than the preceding TS3 and TS3′, which is of importance for the analysis of the selectivity (see below). The rhodium hydride complexes resulting from the β-elimination (INT6 and INT6′) are octahedral and contain an η¹-allyl and a carbonyl oxygen coordinated to the metal.

Figure 6. Optimized structures of the β-hydride elimination transition states and the resulting η¹-allyl complexes.

We also considered an alternative process that theoretically may interfere with the β-hydride elimination from INT5 or INT5′, namely, a C–O bond-forming reductive elimination. With such a course, the reaction would yield pyrane derivatives as products and thus would constitute a heteroatom analogue of the [2 + 2 + 2] carbocyclization shown in Scheme 1a. (23) However, the calculated barrier for this process (from INT5′ to TS-RE′) was found to be 26.9 kcal/mol, which is 16.8 kcal/mol higher than for the β-elimination from the same intermediate (Figure 5). Hence, the C–O bond-forming reductive elimination should not take place, which is indeed the result observed experimentally.

3.4 Reductive Elimination

The last step of the mechanism, closing the catalytic cycle, is the C–H bond-forming reductive elimination (Scheme 3). This could occur directly from INT6 and INT6′. The calculated free energy barriers are quite feasible (20.4 and 19.2 kcal/mol from INT6 and INT6′, respectively; see the Supporting Information for the optimized structures of the TSs). However, if the reaction were to follow this pathway, it would yield only compounds 4 and 5 as products rather than the experimentally observed mixture containing predominantly their isomer 3. Prompted by this apparent flaw, we envisioned that the η¹-allylic complexes INT6 and INT6′ could be converted into their η³-allylic counterparts INT7 and INT7′, respectively, upon dissociation of the carbonyl oxygen from the rhodium center prior to the reductive elimination. The fact that both terminal carbon atoms of the η³-allyl systems in INT7 and INT7′ can couple with the hydride during the reductive elimination would enable the formation of 3 in such a transformation.

Indeed, as shown in Figure 7, the Rh(III) hydrides containing the η³-allyl ligand, INT7 and INT7′ (see Figure 8 for the structures), are more stable than INT6 and INT6′ by 1.1 and 5.3 kcal/mol, respectively. (24) As mentioned above, from INT7 and INT7′ the reductive elimination can occur at either the C1 or C3 side of the η³-allyl. The calculations showed that irrespective of the starting complex, the reductive elimination engaging the methyl-substituted carbon C3 (TS5a and TS5a′) is more favorable than the one occurring at the unsubstituted carbon C1 (TS5b and TS5b′; Figure 7). This is typical behavior in many Rh-catalyzed reactions involving π-allyl species, which usually afford the branched product. (19a-19m) One reason for this preference is that in TS5a and TS5a′ the sterically crowded rhodium center is positioned closer to the less-substituted double bond (between C1 and C2). For example, in TS5a′, the bond distances of Rh–C1 and Rh–C2 are 2.15 and 2.16 Å, respectively, whereas in TS5b′, because of the steric effect of methyl group, the Rh–C2 and Rh–C3 bond distances are somewhat longer (2.19 and 2.22 Å, respectively) (Figure 8). Importantly, the free energies of all of the TS5 variants are lower than those of the transition states for the direct reductive elimination from INT6 and INT6′, implying that the reaction does not follow the latter pathway. (25) The influence of the relative energies of the reductive elimination transition states on the overall selectivity of the reaction will be discussed in the following section.

Figure 7. Free energy profile for the reductive elimination step.

Figure 8. Optimized structures of the reductive elimination reactants and transition states.

3.5 Overall Catalytic Cycle and Origins of the Regioselectivity in the [RhCl(dppe)]-Catalyzed Reaction

The mechanism of the reaction as established by the present DFT calculations is summarized in Scheme 6, and the corresponding overall free energy profile is given in Figure 9. The catalytic cycle consists of four steps: (1) oxidative coupling of two allene molecules, (2) allylation of the aldehyde, (3) β-hydride elimination, and (4) C–H bond-forming reductive elimination. A prominent role in the mechanism is played by allylrhodium complexes. Because of the flexibility of the allyl ligand binding modes (η³, η¹), a variety of reactivity patterns at each step of the catalytic cycle are available. Hence, the mechanism of the reaction involving allenes displays considerable differences compared with the mechanism of the related reductive coupling of acetylene and aldehyde shown in Scheme 2a, (9) in which vinyl ligands limited only to σ bonding are involved.

Scheme 6. Summary of the Mechanism of the [RhCl(dppe)]-Catalyzed 1:2 Coupling of Aldehydes and Allenes

Figure 9. Free energy profile for the [RhCl(dppe)]-catalyzed 1:2 coupling of aldehydes and allenes.

The oxidative coupling of two allene molecules (TS1) is a common step in all of the pathways leading to the experimentally observed products 3–5. It has a barrier of 21.5 kcal/mol relative to the most stable Rh(I) complex, INT1. The oxidative coupling is irreversible and leads selectively to the octahedral η³,η¹-bis(allylic) Rh(III) complex INT2, which has a well-defined and stable stereochemical configuration. Therefore, in this step of the mechanism, a number of structural features of the products are already determined, such as the C2–C2 linkage and the configuration of the double bonds. It is also important to point out that the overall barrier for the oxidative coupling is the highest among all of the barriers in the catalytic cycle. This step therefore constitutes the rate-determining step of the reaction.

Upon coordination of an aldehyde molecule, INT2 undergoes a transformation to either INT3 or INT3′, depending on which side of the η³-allyl ligand remains bound to the metal (C1 or C3, respectively). Thus, this step constitutes the first divergence point, from which the two pathways proceed through the subsequent steps separately. The following step is the allylation of the aldehyde, which proceeds through the six-membered cyclic transition states TS2 and TS2′. After an isomerization (INT4 → INT5 via TS3 and INT4′ → INT5′ via TS3′) that is needed to create an empty coordination site in an appropriate position of the complex, a β-hydride elimination takes place via TS4 and TS4′. Since TS3 and TS3′ are higher in energy than all of the subsequent transition states, passing them can be considered practically irreversible. Therefore, the ratio at which the catalyst is split to follow either one or the other branch of the catalytic cycle is determined by the free energy difference between the transition states TS3 and TS3′. According to the calculations, these free energies differ by 2.0 kcal/mol, and hence, intermediates INT6 and INT6′ are formed in a 5:95 ratio. (26)

The next step of the mechanism is the C–H bond-forming reductive elimination, which starts with conversion of the η¹-allylic Rh(III) hydrides INT6 and INT6′ to the η³-allylic species INT7 and INT7′, respectively. The reductive elimination is the final regioselectivity-determining step. This process was found to take place preferentially at the C3 position (TS5a and TS5a′) rather than at C1 (TS5b and TS5b′). In particular, from INT7′, the formation of INT8a′ via TS5a′ is favored over the formation of INT8b′ via TS5b′ by 2.3 kcal/mol. This free energy difference corresponds approximately to a 98:2 ratio. On the other hand, the 5.3 kcal/mol free energy difference between TS5a and TS5b implies the practically exclusive transformation of INT7 into INT8a. Hence, when the previous split of the reaction pathways is taken into account, the overall selectivity predicted by the calculations is 3:4:5 = 93:2:5, which is in very good agreement with the experimentally observed ratio of 91:6:3 (Scheme 2b). (6)

Finally, intermediates INT8a′, INT8b′, and INT8a formed in the reductive elimination regenerate the free catalyst [RhCl(dppe)] by releasing the corresponding products 3, 4, and 5, respectively, closing the catalytic cycle. It should be pointed out that the relative stabilities of the free products 3, 4, and 5 do not correlate at all with their ratios resulting from the catalyzed reaction.

In summary, the above considerations show that the calculated energies can reproduce and rationalize the observed selectivity of the [RhCl(dppe)]-catalyzed reaction, which provides further support for the reaction mechanism suggested in Scheme 6.

3.6 Regioselectivity in the [Rh(dppe)]⁺-Catalyzed Reaction

As mentioned in the Introduction, the selectivity of the reaction can be altered by replacing the chloride anion in the catalyst precursor with a noncoordinating counterion such as TfO^–, BF₄^–, or PF₆^–. To rationalize this catalyst-dependent selectivity, we reinvestigated the reaction mechanism with the cationic [Rh(dppe)]⁺ complex as the active species. The calculations suggested that the cationic catalyst promotes a partially different mechanistic pathway (see Scheme 7 for the mechanism and Figure 10 for calculated energy profile), which in turn causes the alteration of the selectivity.

Scheme 7. Summary of the Mechanism of the [Rh(dppe)]⁺-Catalyzed 1:2 Coupling of Aldehydes and Allenes

Figure 10. Free energy profile for the [Rh(dppe)]⁺-catalyzed 1:2 coupling of aldehydes and allenes.

The first two steps of the mechanism are the same as for the [RhCl(dppe)] catalyst, except for the fact that because of the availability of an extra coordination site in the cationic catalyst, the initial INT1⁺ complex contains two allene molecules. The reaction starts with oxidative coupling of the two allene moieties (TS1⁺), resulting in the selective formation of η³,η¹-bis(allylic) complex INT2⁺. The structure of the allylic ligand in INT2⁺ is identical to that in INT2, thus limiting the possible reaction products to 3–6 as discussed above for the neutral [RhCl(dppe)] catalyst. It should be noted that this step is also rate-determining for this catalyst. The next step is allylation of the aldehyde via TS2⁺ and TS2′⁺, resulting in intermediates INT4⁺ and INT4′⁺, respectively. The selectivity of the allylation is the same as before, that is, the allylation occurs preferentially at the C3 position via TS2⁺.

From INT4⁺ and INT4′⁺, the reaction can follow the same isomerization/β-hydride elimination/reductive elimination pathway found for the neutral catalyst. The optimized geometries and calculated energy profile for this scenario are given in the Supporting Information. Similarly to the neutral catalyst, the highest barrier was calculated to occur for the isomerization (TS3⁺ and TS3′⁺), amounting to 12.0 and 12.2 kcal/mol relative to INT4⁺ and INT4′⁺, respectively. However, although the energy barriers are feasible, if such an analogous pathway were followed, it would lead to the same selectivity as before (i.e., predominantly product 3; see the Supporting Information). This is in conflict with the experimental findings, which thus speaks against such a mechanism for the cationic catalyst.

Instead, we discovered an alternative mechanism that reproduces the reversed selectivity observed with the cationic catalyst. The alkoxide ligand present in the Rh(III) complexes INT4⁺ and INT4′⁺ can undergo a feasible direct oxidation to give the corresponding ketones (TS6⁺ and TS6′⁺; see Figure 11 for the optimized structures). In the course of the reaction, Rh(III) is reduced to Rh(I) and the final products 3 and 5 are formed directly (coordinated to the metal as INT9′⁺ and INT9⁺, respectively). A key role in this process is played by the η¹-allyl ligand, which acts as an internal base to abstract a proton from the alkoxide (Figure 11). Although perhaps somewhat surprising in this context, this transformation is analogous to the well-known oxidation of alcohols by high-valent metals, such as Mn(VII) and Cr(VI). (27) The example of related oxidation in Pd(II) complexes has also been reported. (28)

Figure 11. Optimized structures of the alkoxide oxidation transition states **TS6**⁺ and **TS6′**⁺.

The barriers for TS6⁺ and TS6′⁺ relative to INT4⁺ and INT4′⁺, respectively, were calculated to be 10.1 and 12.0 kcal/mol, respectively. As shown in the free energy profile in Figure 10, the regioselectivity in this case is controlled by the free energy difference between TS2′⁺ and TS6⁺, which constitute the first irreversible steps in the respective pathways leading to the two products. The calculated free energy difference between these transition states is 0.3 kcal/mol, corresponding to a 3:5 ratio of 40:60.

Although the difference in the free energy barriers for the isomerization/β-hydride elimination/reductive elimination pathway (12.0 and 12.2 kcal/mol for TS3⁺ and TS3′⁺, respectively) and the alkoxide oxidation pathway (10.1 and 12.0 kcal/mol for TS6⁺ and TS6′⁺, respectively) is not so large that the former one can be completely ruled out, the fact that the alkoxide oxidation mechanism can account for the reversal of selectivity in the cationic catalyst is a strong argument in favor of it. Another piece of evidence is that the alkoxide oxidation via TS6⁺ and TS6′⁺ leads directly to compounds 3 and 5, which explains why these are the only products observed experimentally in the reaction involving the cationic catalyst, while for the neutral catalyst, on the other hand, three products are observed.

Finally, it should be mentioned that we also located transition states for a similar alkoxide oxidation mechanism in the chloride-containing neutral complexes INT4 and INT4′. However, the barriers were found to be much higher than those in the isomerization/β-hydride elimination/reductive elimination pathway discussed above (see the Supporting Information for details). Hence, the electron-deficient character of rhodium in the cationic complex is crucial for the alkoxide oxidation reaction.

4 Conclusions

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The rhodium-catalyzed 1:2 coupling of aldehydes and allenes has been investigated in detail by DFT calculations. The free energy profiles for several possible reaction pathways have been calculated and compared.

For the reaction catalyzed by the neutral [RhCl(dppe)] complex, it has been shown that the energetically most plausible catalytic cycle consists of the following steps: oxidative coupling of the two allenes, allylation of the aldehyde, β-hydride elimination, and finally reductive elimination. The first step was found to be rate-determining for the overall reaction, and it leads to the formation of a bis(allylic) Rh(III) complex. Because of its ability to adopt either an η³ or η¹ configuration, the allyl ligand turns out to play a key role throughout the mechanism, with profound consequences for the reaction selectivity.

The calculations showed that the remarkable regioselectivity of the reaction is an overall result of a number of selection events that take place in the catalytic cycle. The first regioselectivity-determining step is the oxidative coupling, in which the C2–C2 linkage between the allene moieties is selectively established. Subsequently, the selectivity of the second C–C bond formation is controlled during the β-hydride elimination. Finally, the reductive elimination was found to yield the branched product preferentially.

For the reaction catalyzed by the cationic [Rh(dppe)]⁺ complex, on the other hand, the calculations suggested a different reaction mechanism after the allylation step. Namely, oxidation of the alkoxide can take place directly to yield the products. This important difference explains the experimentally observed reversal of selectivity.

The present calculations thus provide important insights into the mechanism of rhodium(I)-catalyzed coupling reactions, in particular those involving allenes, and will have a general bearing on the improvement of existing catalytic systems and the design of new ones.

Supporting Information

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Complete ref 13, additional results not shown in the text, and Cartesian coordinates of all optimized structures discussed in the paper. This material is available free of charge via the Internet at http://pubs.acs.org.

ja4014166_si_001.pdf (8.97 MB)

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Author Information

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Corresponding Author
- Fahmi Himo - Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
Authors
- Genping Huang - Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- Marcin Kalek - Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
Notes
The authors declare no competing financial interest.

Acknowledgment

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We acknowledge financial support from the Swedish Research Council, the Göran Gustafsson Foundation, and the Knut and Alice Wallenberg Foundation. G.H. thanks the Carl Trygger Foundation for a postdoctoral fellowship. Computer time was generously provided by the Swedish National Infrastructure for Computing.

References

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This article references 28 other publications.

1
(a) Lautens, M.; Klute, W.; Tam, W. Chem. Rev. 1996, 96, 49– 92
Google Scholar
1a
Transition Metal-Mediated Cycloaddition Reactions
Lautens, Mark; Klute, Wolfgang; Tam, William
Chemical Reviews (Washington, D. C.) (1996), 96 (1), 49-92CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review with 226 refs. A discussion of established and interesting new cycloaddn. reactions promoted by metal species is presented.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XjsVKktw%253D%253D&md5=3776dd13a62c7dbef311a7cbf457dd7f
(b) Kotha, S.; Brahmachary, E.; Lahiri, K. Eur. J. Org. Chem. 2005, 4741– 4767
Google Scholar
1b
Transition metal-catalyzed [2+2+2] cycloaddition and application in organic synthesis
Kotha, Sambasivarao; Brahmachary, Enugurthi; Lahiri, Kakali
European Journal of Organic Chemistry (2005), (22), 4741-4767CODEN: EJOCFK; ISSN:1434-193X. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. The [2+2+2] cycloaddn. strategy is complementary to the well known Diels-Alder reaction for the generation of polycyclic compds. This [2+2+2] approach is atom-economical and, with the availability of new catalysts to effect the [2+2+2] cycloaddn. reaction, synthesis of a wide variety of highly functionalized polycycles is possible. This review deals with some recent advances relating to [2+2+2] cycloaddn. reactions involving the syntheses both of polycycles and of heterocycles. More specifically, syntheses of various biol. active mols., unusual amino acids, and theor. interesting mols. are described. An attempt has also been made to give an overview of recent advances in the achievement of chemo-, regio-, and stereoselectivity in cyclotrimerization reactions.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1KgurrM&md5=93220a4594f4dfa8e3cf02aac00ba43a
(c) Murakami, M. Angew. Chem., Int. Ed. 2003, 42, 718– 720
Google Scholar
There is no corresponding record for this reference.
(d) Inglesby, P. A.; Evans, P. A. Chem. Soc. Rev. 2010, 39, 2791– 2805
Google Scholar
1d
Stereoselective transition metal-catalysed higher-order carbocyclisation reactions
Inglesby, Phillip A.; Evans, P. Andrew
Chemical Society Reviews (2010), 39 (8), 2791-2805CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
A review. Transition metal-catalyzed higher-order carbocyclization reactions represent an important class of reactions due to their ability to construct complex polycyclic systems in a highly selective and atom-economical fashion. A key and striking feature with these transformations is the dichotomy in reactivity that a substrate displays with different transition metal complexes, which is akin to the manner enzymes direct terpene biosynthesis. This tutorial review details the historical development of higher-order carbocyclization reactions, specifically the variants of [m+2+2] that involve carbon-based π-systems, where m = 2, 3 and 4, in the context of crit. developments with various transition metal complexes.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptFyhu7c%253D&md5=f8e29c1b1b3795588b1be0f7e9c11a97
(e) Shibata, T.; Tsuchikama, K. Org. Biomol. Chem. 2008, 6, 1317– 1323
Google Scholar
There is no corresponding record for this reference.
(f) Tanaka, K. Chem.—Asian J. 2009, 4, 508– 518
Google Scholar
1f
Transition-metal-catalyzed enantioselective [2+2+2] cycloadditions for the synthesis of axially chiral biaryls
Tanaka, Ken
Chemistry - An Asian Journal (2009), 4 (4), 508-518CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. Recent advances towards a development of novel transition-metal-catalyzed enantioselective [2+2+2] cycloaddn. for the synthesis of axially chiral biaryls are reviewed. A no. of efficient enantioselective biaryl syntheses were accomplished by chiral cobalt(I), iridium(I), and rhodium(I) complex catalyzed [2+2+2] cycloaddn. Furthermore, the enantioselective synthesis of axially chiral biaryls possessing non-biaryl axial chirality was also developed by using chiral rhodium(I) complexes as catalysts.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXks1Cht7c%253D&md5=941a1af8b94d4a5e67af5a6b0f552d64
(g) Yu, Z.-X.; Wang, Y.; Wang, Y. Chem.—Asian J. 2010, 5, 1072– 1088
Google Scholar
1g
Transition-metal-catalyzed cycloadditions for the synthesis of eight-membered carbocycles
Yu, Zhi-Xiang; Wang, Yi; Wang, Yuanyuan
Chemistry - An Asian Journal (2010), 5 (5), 1072-1088CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. Eight-membered carbocycles are in a wide variety of natural products that exhibit a broad range of biol. and medicinal activities (cf. the most potent anticancer drug, taxol). However, the synthesis of eight-membered carbocycles is quite challenging as traditional approaches are met with entropic and enthalpic penalties in the ring-forming transition states. These neg. effects can be totally or partially avoided with the implementation of transition-metal-catalyzed/mediated cycloaddns. In this focus review, examples of elegant and efficient metal-catalyzed and some metal-mediated cycloaddns. (including Ni- catalyzed [4+4] and Rh-catalyzed [4+2+2] and [5+2+1] reactions) are presented to illustrate this. Application of these cycloaddn. reactions in total synthesis was also presented to show the significance of these reactions in addressing challenges in natural product synthesis.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXls1Wkur8%253D&md5=867a869887dd578c5621f6992c3b6319
2
(a) Willis, M. C. Chem. Rev. 2010, 110, 725– 748
Google Scholar
2a
Transition Metal Catalyzed Alkene and Alkyne Hydroacylation
Willis, Michael C.
Chemical Reviews (Washington, DC, United States) (2010), 110 (2), 725-748CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
This review is a coordinated anal. of the intramol. or intermol. alkene hydroacylation using transition metal catalysts. The mechanism of such transformations is also presented in this systematic review.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtleisL3N&md5=bd9108b8b2ab0b60865cdd64044736fa
(b) Jun, C.-H.; Moon, C. W.; Lee, D.-Y. Chem.—Eur. J. 2002, 8, 2422– 2428
Google Scholar
2b
Chelation-assisted carbon-hydrogen and carbon-carbon bond activation by transition metal catalysts
Jun, Chul-Ho; Moon, Choong Woon; Lee, Dae-Yon
Chemistry - A European Journal (2002), 8 (11), 2422-2428CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH)
A review with refs. on the chelation-assisted C-H and C-C bond activation of carbonyl compds. by RhI catalysts. Hydroacylation of olefins was accomplished by utilizing 2-amino-3-picoline as a chelation auxiliary. The same strategy was employed for the C-C bond activation of unstrained ketones. Allylamine 24 was devised as a synthon of formaldehyde. Hydroiminoacylation of alkynes with allylamine 24 was applied to the alkyne cleavage by the aid of cyclohexylamine.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XksFWgs7s%253D&md5=9f3fa5e5d3340dfb3541509a40f2bcc3
(c) Leung, J. C.; Krische, M. J. Chem. Sci. 2012, 3, 2202– 2209
Google Scholar
2c
Catalytic intermolecular hydroacylation of C-C π-bonds in the absence of chelation assistance
Leung, Joyce C.; Krische, Michael J.
Chemical Science (2012), 3 (7), 2202-2209CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
A review. Intermol. rhodium catalyzed hydroacylation in the absence of chelation assistance remains a largely unmet challenge due to competing decarbonylation of the acylrhodium intermediates to form catalytically inactive carbonyl complexes. Here, catalytic systems for intermol. hydroacylation in the absence of chelation assistance are reviewed, with an emphasis on recently described processes that operate through mechanistic pathways beyond aldehyde C-H oxidative addn.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XotFGku7g%253D&md5=551e827a85202d1ca97cfff97e5b5ec4
3
(a) Jang, H.-Y.; Krische, M. J. Acc. Chem. Res. 2004, 37, 653– 661
Google Scholar
There is no corresponding record for this reference.
(b) Ngai, M.-Y.; Kong, J.-R.; Krische, M. J. J. Org. Chem. 2007, 72, 1063– 1072
Google Scholar
There is no corresponding record for this reference.
(c) Iida, H.; Krische, M. J. Top. Curr. Chem. 2007, 279, 77– 104
Google Scholar
There is no corresponding record for this reference.
(d) Bower, J. F.; Kim, I. S.; Patman, R. L.; Krische, M. J. Angew. Chem., Int. Ed. 2009, 48, 34– 46
Google Scholar
There is no corresponding record for this reference.
(e) Skucas, E.; Ngai, M.-Y.; Komanduri, V.; Krische, M. J. Acc. Chem. Res. 2007, 40, 1394– 1401
Google Scholar
There is no corresponding record for this reference.
4
Kong, J. R.; Krische, M. J. J. Am. Chem. Soc. 2006, 128, 16040– 16041
Google Scholar
4
Catalytic Carbonyl Z-Dienylation via Multicomponent Reductive Coupling of Acetylene to Aldehydes and α-Ketoesters Mediated by Hydrogen: Carbonyl Insertion into Cationic Rhodacyclopentadienes
Kong, Jong Rock; Krische, Michael J.
Journal of the American Chemical Society (2006), 128 (50), 16040-16041CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Exposure of aldehydes or α-ketoesters to equal vols. of acetylene and hydrogen gas at ambient temp. and pressure in the presence of cationic rhodium catalysts provides products of carbonyl Z-butadienylation, which arise via multicomponent coupling of four mols.: two mols. of acetylene, a mol. of vicinal dicarbonyl compd., and a mol. of elemental hydrogen. The collective data suggest a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene intermediate derived via oxidative dimerization of acetylene. Hydrogenolytic cleavage of the resulting oxarhodacycloheptadiene via formal σ-bond metathesis provides the product of carbonyl addn. and cationic rhodium(I) to close the catalytic cycle. Studies involving the hydrogenation of 1,6-diyne 14a (I) in the presence of α-ketoester 6a (II) corroborate the proposed catalytic mechanism. These multicomponent couplings represent the first use of acetylene gas, a basic chem. feedstock, in metal-catalyzed reductive C-C bond formation.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1GjsLvO&md5=4fed0d21910ffedc7657e0f145866142
5
The reaction scope was later expanded by inclusion of other aldehydes and imines as coupling partners. See:
(a) Skucas, E.; Kong, J. R.; Krische, M. J. J. Am. Chem. Soc. 2007, 129, 7242– 7243
Google Scholar
5a
Enantioselective Reductive Coupling of Acetylene to N-Arylsulfonyl Imines via Rhodium Catalyzed C-C Bond-Forming Hydrogenation: (Z)-Dienyl Allylic Amines
Skucas, Eduardas; Kong, Jong Rock; Krische, Michael J.
Journal of the American Chemical Society (2007), 129 (23), 7242-7243CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The first highly enantioselective catalytic vinylation of aldimines to furnish allylic amines is reported. Exposure of arom. and aliph. N-arylsulfonyl aldimines to equal vols. of acetylene and hydrogen gas at 45 °C and ambient pressure in the presence of chirally modified cationic rhodium catalysts provides the (Z)-dienyl allylic amines, e.g., I, in highly optically enriched form (93-98% ee) and as single geometrical isomers (>95:5, Z/E). The coupling products arise via multicomponent coupling of four mols.: two mols. of acetylene, a mol. of aldimine, and elemental hydrogen. Unlike other imine addns. involving nonstabilized carbanions, the present protocol circumvents use of preformed organometallic reagents.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXlsVKjtL4%253D&md5=a7e874a53cbb7c68ca588ab664b01ab6
(b) Han, S. B.; Kong, J. R.; Krische, M. J. Org. Lett. 2008, 10, 4133– 4135
Google Scholar
There is no corresponding record for this reference.
6
Toyoshima, T.; Miura, T.; Murakami, M. Angew. Chem., Int. Ed. 2011, 50, 10436– 10439
Google Scholar
6
Selective 1:2 Coupling of Aldehydes and Allenes with Control of Regiochemistry
Toyoshima, Takeharu; Miura, Tomoya; Murakami, Masahiro
Angewandte Chemie, International Edition (2011), 50 (44), 10436-10439, S10436/1-S10436/72CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A new rhodium-catalyzed coupling reaction of one mol. of aldehyde and two mol. of allene was developed and gave selectively either of two constitutional isomers of β,γ-dialkylidene ketones, e.g. I and II. Interestingly, the regioselectivity of the reaction depends on the counterion of a rhodium(I) complex.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtFOlsLnF&md5=671aecf04716fd7642c2c48cb11cad4e
7
(a) Oonishi, Y.; Hosotani, A.; Sato, Y. J. Am. Chem. Soc. 2011, 133, 10386– 10389
Google Scholar
7a
Rh(I)-Catalyzed Formal [6 + 2] Cycloaddition of 4-Allenals with Alkynes or Alkenes in a Tether
Oonishi, Yoshihiro; Hosotani, Akihito; Sato, Yoshihiro
Journal of the American Chemical Society (2011), 133 (27), 10386-10389CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Rh(I)-catalyzed formal [6 + 2] cycloaddn. of allenal, e.g., I, having an alkyne or alkene in a tether proceeded smoothly, giving fused bicyclic ketone derivs., e.g., II, in good to excellent yields. It was also found that cyclization of enantiomerically enriched I (94% ee) gave cyclic ketone deriv. II in high yield with reasonable chirality transfer (86% ee). This result indicates that this cyclization proceeds through stereoselective formation of rhodacycle H' followed by insertion of a multiple bond.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXns1enu70%253D&md5=71bb3766dfa4cc0ebc76992057e5c9d9
(b) Hojo, D.; Tanaka, K. Org. Lett. 2012, 14, 1492– 1495
Google Scholar
7b
Rhodium-Catalyzed C-H Bond Activation/[4+2] Annulation/Aromatization Cascade To Produce Phenol, Naphthol, Phenanthrenol, and Triphenylenol Derivatives
Hojo, Daiki; Tanaka, Ken
Organic Letters (2012), 14 (6), 1492-1495CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
It has been established that a cationic rhodium(I)/dppp complex catalyzes the aldehyde C-H bond activation/[4 + 2] annulation/aromatization cascade to produce phenol, naphthol, phenanthrenol, and triphenylenol derivs. from readily available conjugated alkynyl aldehydes and alkynes.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XivVOht7o%253D&md5=b2c27512626dc31fb7185f1ced643811
8
The total of 36 refers only to the number of possible linear compounds containing the reactant molecules coupled in a aldehyde–allene–allene sequence. In fact, two of the above isomers contain two asymmetric carbon atoms and hence can exist as two diastereomers, raising the number of possible products with distinct energies to 38. If cyclic structures and those containing allene–aldehyde–allene sequence are also considered, the number of possible products is even greater.
There is no corresponding record for this reference.
9
Williams, V. M.; Kong, J. R.; Ko, B. J.; Mantri, Y.; Brodbelt, J. S.; Baik, M.-H.; Krische, M. J. J. Am. Chem. Soc. 2009, 131, 16054– 16062
Google Scholar
There is no corresponding record for this reference.
10
Miura, T.; Biyajima, T.; Toyoshima, T.; Murakami, M. Beilstein J. Org. Chem. 2011, 7, 578– 581
Google Scholar
10
Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes
Miura, Tomoya; Biyajima, Tsuneaki; Toyoshima, Takeharu; Murakami, Masahiro
Beilstein Journal of Organic Chemistry (2011), 7 (), 578-581, No. 67CODEN: BJOCBH; ISSN:1860-5397. (Beilstein-Institut zur Foerderung der Chemischen Wissenschaften)
A rhodium(I)/dppe catalyst promoted dimerization of monosubstituted allenes in a stereoselective manner to give cross-conjugated trienes, which are different from those obtained by a palladium catalyst. A palladium-catalyzed reaction of 1,2-undecadiene delivered the previously reported 11-methyl-10-methylene-8,11-eicosadiene and a new product [i.e., (8E)-10,11-bis(methylene)-8-eicosene]. [4+2] Cycloaddn. products of (8E)-10,11-bis(methylene)-8-eicosene with 1,1,2,2-ethenetetracarbonitrile and 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione were reported.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmsV2itb4%253D&md5=6ed76f458f528c62436bb4c886c73d5d
11
In fact, to the best of our knowledge, all of the transition-metal-catalyzed [n + m + o] cycloadditions involving allenes developed to date incorporate only one or two molecules of allene into the product. See:
(a) Murakami, M.; Ubukata, M.; Itami, K.; Ito, Y. Angew. Chem., Int. Ed. 1998, 37, 2248– 2250
Google Scholar
There is no corresponding record for this reference.
(b) Shanmugasundaram, M.; Wu, M.-S.; Cheng, C.-H. Org. Lett. 2001, 3, 4233– 4236
Google Scholar
There is no corresponding record for this reference.
(c) Shanmugasundaram, M.; Wu, M.-S.; Jeganmohan, M.; Huang, C.-W.; Cheng, C.-H. J. Org. Chem. 2002, 67, 7724– 7729
Google Scholar
There is no corresponding record for this reference.
(d) Miura, T.; Morimoto, M.; Murakami, M. J. Am. Chem. Soc. 2010, 132, 15836– 15838
Google Scholar
There is no corresponding record for this reference.
(e) Brusoe, A. T.; Alexanian, E. J. Angew. Chem., Int. Ed. 2011, 50, 6596– 6600
Google Scholar
There is no corresponding record for this reference.
12
(a) McCarren, P. R.; Liu, P.; Cheong, P. H.-Y.; Jamison, T. F.; Houk, K. N. J. Am. Chem. Soc. 2009, 131, 6654– 6655
Google Scholar
There is no corresponding record for this reference.
(b) Liu, P.; McCarren, P.; Cheong, P. H.-Y.; Jamison, T. F.; Houk, K. N. J. Am. Chem. Soc. 2010, 132, 2050– 2057
Google Scholar
12b
Origins of Regioselectivity and Alkene-Directing Effects in Nickel-Catalyzed Reductive Couplings of Alkynes and Aldehydes
Liu, Peng; McCarren, Patrick; Cheong, Paul Ha-Yeon; Jamison, Timothy F.; Houk, K. N.
Journal of the American Chemical Society (2010), 132 (6), 2050-2057CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The origins of reactivity and regioselectivity in nickel-catalyzed reductive coupling reactions of alkynes and aldehydes were investigated with d. functional calcns. The regioselectivities of reactions of simple alkynes are controlled by steric effects, while conjugated enynes and diynes are predicted to have increased reactivity and very high regioselectivities, placing alkenyl or alkynyl groups distal to the forming C-C bond. The reactions of enynes and diynes involve 1,4-attack of the Ni-carbonyl complex on the conjugated enyne or diyne. The consequences of these conclusions on reaction design are discussed.
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(c) Liu, P.; Krische, M. J.; Houk, K. N. Chem.—Eur. J. 2011, 17, 4021– 4029
Google Scholar
12c
Mechanism and Origins of Regio- and Enantioselectivities in RhI-Catalyzed Hydrogenative Couplings of 1,3-Diynes and Activated Carbonyl Partners: Intervention of a Cumulene Intermediate
Liu, Peng; Krische, Michael J.; Houk, Kendall N.
Chemistry - A European Journal (2011), 17 (14), 4021-4029, S4021/1-S4021/24CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
The mechanism of the rhodium-catalyzed reductive coupling of 1,3-diynes and vicinal dicarbonyl compds. employing H2 as reductant was studied by d. functional theory. Oxidative coupling through 1,4-addn. of the RhI-bound dicarbonyl to the conjugated diyne via a seven-membered cyclic cumulene transition state leads to exclusive formation of linear adducts. Diyne 1,4-addn. is much faster than the 1,2-addn. to simple alkynes. The 1,2-dicarbonyl compd. is bound to rhodium in a bidentate fashion during the oxidative coupling event. The chemo-, regio-, and enantioselectivities of this reaction were studied and are attributed to this unique 1,4-addn. pathway. The close proximity of the ligand and the alkyne substituent distal to the forming C-C bond controls the regio- and enantioselectivity: coupling occurs at the sterically more demanding alkyne terminus, which minimizes nonbonded interaction with the ligand. A stereochem. model is proposed that accounts for preferential formation of the (R)-configurated coupling product when (R)-biaryl phosphine ligands are used.
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13
Frisch, M. J.; Gaussian 03, revision D.01; Gaussian, Inc.: Wallingford, CT, 2004.
Google Scholar
There is no corresponding record for this reference.
14
(a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648– 5652
Google Scholar
14a
Density-functional thermochemistry. III. The role of exact exchange
Becke, Axel D.
Journal of Chemical Physics (1993), 98 (7), 5648-52CODEN: JCPSA6; ISSN:0021-9606.
Despite the remarkable thermochem. accuracy of Kohn-Sham d.-functional theories with gradient corrections for exchange-correlation, the author believes that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional (contg. local-spin-d., gradient, and exact-exchange terms) is tested for 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total at. energies of first- and second-row systems. This functional performs better than previous functionals with gradient corrections only, and fits expt. atomization energies with an impressively small av. abs. deviation of 2.4 kcal/mol.
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(b) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785– 789
Google Scholar
14b
Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
Lee, Chengteh; Yang, Weitao; Parr, Robert G.
Physical Review B: Condensed Matter and Materials Physics (1988), 37 (2), 785-9CODEN: PRBMDO; ISSN:0163-1829.
A correlation-energy formula due to R. Colle and D. Salvetti (1975), in which the correlation energy d. is expressed in terms of the electron d. and a Laplacian of the 2nd-order Hartree-Fock d. matrix, is restated as a formula involving the d. and local kinetic-energy d. On insertion of gradient expansions for the local kinetic-energy d., d.-functional formulas for the correlation energy and correlation potential are then obtained. Through numerical calcns. on a no. of atoms, pos. ions, and mols., of both open- and closed-shell type, it is demonstrated that these formulas, like the original Colle-Salvetti formulas, give correlation energies within a few percent.
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15
Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270– 283
Google Scholar
15
Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms scandium to mercury
Hay, P. Jeffrey; Wadt, Willard R.
Journal of Chemical Physics (1985), 82 (1), 270-83CODEN: JCPSA6; ISSN:0021-9606.
Ab initio effective core potentials (ECP's) were generated to replace the Coulomb, exchange, and core-orthogonality effects of the chem. inert core electron in the transition metal atoms Sc to Hg. For the second and third transition series relative ECP's were generated which also incorporate the mass-velocity and Darwin relativistic effects into the potential. The ab initio ECP's should facilitate valence electron calcns. on mols. contg. transition-metal atoms with accuracies approaching all-electron calcns. at a fraction of the computational cost. Analytic fits to the potentials are presented for use in multicenter integral evaluation. Gaussian orbital valence basis sets are developed for the (3d,4s,4p), (4d,5s,5p), and (5d,6s,6p) orbitals of the first, second, and third transition series atoms, resp. All-electron and valence-electron at. excitation energies are also compared for the low-lying states of Sc-Hg, and the valence-electron calcns. reproduce the all-electron excitation energies (typically within a few tenths of an eV).
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16
(a) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995– 2001
Google Scholar
16a
Quantum Calculation of Molecular Energies and Energy Gradients in Solution by a Conductor Solvent Model
Barone, Vincenzo; Cossi, Maurizio
Journal of Physical Chemistry A (1998), 102 (11), 1995-2001CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
A new implementation of the conductor-like screening solvation model (COSMO) in the GAUSSIAN94 package is presented. It allows Hartree-Fock (HF), d. functional (DF) and post-HF energy, and HF and DF gradient calcns.: the cavities are modeled on the mol. shape, using recently optimized parameters, and both electrostatic and nonelectrostatic contributions to energies and gradients are considered. The calcd. solvation energies for 19 neutral mols. in water are found in very good agreement with exptl. data; the solvent-induced geometry relaxation is studied for some closed and open shell mols., at HF and DF levels. The computational times are very satisfying: the self-consistent energy evaluation needs a time 15-30% longer than the corresponding procedure in vacuo, whereas the calcn. of energy gradients is only 25% longer than in vacuo for medium size mols.
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(b) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem. 2003, 24, 669– 681
Google Scholar
16b
Energies, structures, and electronic properties of molecules in solution with the C-PCM solvation model
Cossi, Maurizio; Rega, Nadia; Scalmani, Giovanni; Barone, Vincenzo
Journal of Computational Chemistry (2003), 24 (6), 669-681CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
The conductor-like solvation model, as developed in the framework of the polarizable continuum model (PCM), has been reformulated and newly implemented in order to compute energies, geometric structures, harmonic frequencies, and electronic properties in soln. for any chem. system that can be studied in vacuo. Particular attention is devoted to large systems requiring suitable iterative algorithms to compute the solvation charges: the fast multipole method (FMM) has been extensively used to ensure a linear scaling of the computational times with the size of the solute. A no. of test applications are presented to evaluate the performances of the method.
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17
Grimme, S. J. Comput. Chem. 2006, 27, 1787– 1799
Google Scholar
17
Semiempirical GGA-type density functional constructed with a long-range dispersion correction
Grimme, Stefan
Journal of Computational Chemistry (2006), 27 (15), 1787-1799CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
A new d. functional (DF) of the generalized gradient approxn. (GGA) type for general chem. applications termed B97-D is proposed. It is based on Becke's power-series ansatz from 1997 and is explicitly parameterized by including damped atom-pairwise dispersion corrections of the form C6·R-6. A general computational scheme for the parameters used in this correction has been established and parameters for elements up to xenon and a scaling factor for the dispersion part for several common d. functionals (BLYP, PBE, TPSS, B3LYP) are reported. The new functional is tested in comparison with other GGAs and the B3LYP hybrid functional on std. thermochem. benchmark sets, for 40 noncovalently bound complexes, including large stacked arom. mols. and group II element clusters, and for the computation of mol. geometries. Further cross-validation tests were performed for organometallic reactions and other difficult problems for std. functionals. In summary, it is found that B97-D belongs to one of the most accurate general purpose GGAs, reaching, for example for the G97/2 set of heat of formations, a mean abs. deviation of only 3.8 kcal mol-1. The performance for noncovalently bound systems including many pure van der Waals complexes is exceptionally good, reaching on the av. CCSD(T) accuracy. The basic strategy in the development to restrict the d. functional description to shorter electron correlation lengths scales and to describe situations with medium to large interat. distances by damped C6·R-6 terms seems to be very successful, as demonstrated for some notoriously difficult reactions. As an example, for the isomerization of larger branched to linear alkanes, B97-D is the only DF available that yields the right sign for the energy difference. From a practical point of view, the new functional seems to be quite robust and it is thus suggested as an efficient and accurate quantum chem. method for large systems where dispersion forces are of general importance.
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18
For instance, see:
(a) Minenkov, Y.; Occhipinti, G.; Jensen, V. R. J. Phys. Chem. A 2009, 113, 11833– 11844
Google Scholar
There is no corresponding record for this reference.
(b) Siegbahn, P. E. M.; Blomberg, M. R. A.; Chen, S.-L. J. Chem. Theory Comput. 2010, 6, 2040– 2044
Google Scholar
18b
Significant van der Waals Effects in Transition Metal Complexes
Siegbahn, Per E. M.; Blomberg, Margareta R. A.; Chen, Shi-Lu
Journal of Chemical Theory and Computation (2010), 6 (7), 2040-2044CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
There is, in general, very good experience using hybrid DFT to study mechanisms of enzyme reactions contg. transition metals. For redox reactions, the B3LYP* functional, which has 15% exact exchange, has been shown to be particularly accurate. Still, there are some cases which have turned out to be quite difficult with large errors. In the present study, the effects of van der Waals interaction have been investigated for these cases, using the empirical formula of Grimme. The results are encouraging.
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(c) Harvey, J. N. Faraday Discuss. 2010, 145, 487– 505
Google Scholar
There is no corresponding record for this reference.
(d) McMullin, C. L.; Jover, J.; Harvey, J. N.; Fey, N. Dalton Trans. 2010, 39, 10833– 10836
Google Scholar
18d
Accurate modelling of Pd(0) + PhX oxidative addition kinetics
McMullin, Claire L.; Jover, Jesus; Harvey, Jeremy N.; Fey, Natalie
Dalton Transactions (2010), 39 (45), 10833-10836CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
We have used dispersion-cor. DFT (DFT-D) together with solvation to examine possible mechanisms for reaction of PhX (X = Cl, Br, I) with Pd(PtBu3)2 and compare our results to recently published kinetic data (F. Barrios-Landeros, B. P. Carrow and J. F. Hartwig, J. Am. Chem. Soc., 2009, 131, 8141-8154). The calcd. activation free energies agree near-quant. with exptl. obsd. rate consts.
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(e) Lonsdale, R.; Harvey, J. N.; Mulholland, A. J. J. Phys. Chem. Lett. 2010, 1, 3232– 3237
Google Scholar
18e
Inclusion of Dispersion Effects Significantly Improves Accuracy of Calculated Reaction Barriers for Cytochrome P450 Catalyzed Reactions
Lonsdale, Richard; Harvey, Jeremy N.; Mulholland, Adrian J.
Journal of Physical Chemistry Letters (2010), 1 (21), 3232-3237CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
Prediction of cytochrome P 450 reactivity is of great importance to the development of new medicinal compds. D. functional theory (DFT) has proven itself as a useful tool in the characterization of the elusive reactive species, compd. I, and of the mechanisms of substrate oxidn. B3LYP is the most widely used d. functional in the study of P 450s; however, a major drawback of B3LYP is its inaccurate treatment of dispersion, leading to discrepancies between expt. and theory in some systems. Recent work has shown that an added empirical dispersion correction to B3LYP (B3LYP-D) yields more promising results for similar systems. In the present work, two previously studied systems, camphor hydroxylation and alkene oxidn., have been recalcd. using B3LYP-D. Our work shows that inclusion of dispersion has a significant effect on the energies and geometries of transition states and encounter complexes; furthermore, an improved agreement with exptl. data is obsd.
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(f) Osuna, S.; Swart, M.; Solà, M. J. Phys. Chem. A 2011, 115, 3491– 3496
Google Scholar
There is no corresponding record for this reference.
(g) Santoro, S.; Liao, R.-Z.; Himo, F. J. Org. Chem. 2011, 76, 9246– 9252
Google Scholar
There is no corresponding record for this reference.
(h) Nordin, M.; Liao, R.-Z.; Ahlford, K.; Adolfsson, H.; Himo, F. ChemCatChem 2012, 4, 1095– 1104
Google Scholar
There is no corresponding record for this reference.
(i) Xu, X.; Liu, P.; Lesser, A.; Sirois, L. E.; Wender, P. A.; Houk, K. N. J. Am. Chem. Soc. 2012, 134, 11012– 11025
Google Scholar
18i
Ligand Effects on Rates and Regioselectivities of Rh(I)-Catalyzed (5 + 2) Cycloadditions: A Computational Study of Cyclooctadiene and Dinaphthocyclooctatetraene as Ligands
Xu, Xiufang; Liu, Peng; Lesser, Adam; Sirois, Lauren E.; Wender, Paul A.; Houk, K. N.
Journal of the American Chemical Society (2012), 134 (26), 11012-11025CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The first theor. study on the effects of ligands on the mechanism, reactivities, and regioselectivities of Rh(I)-catalyzed (5 + 2) cycloaddns. of vinylcyclopropanes (VCPs) and alkynes has been performed using d. functional theory (DFT) calcns. Highly efficient and selective intermol. (5 + 2) cycloaddns. of VCPs and alkynes have been achieved recently using two novel rhodium catalysts, [Rh(dnCOT)]+SbF6- and [Rh(COD)]+SbF6-, which provide superior reactivities and regioselectivities relative to that of the previously reported [Rh(CO)2Cl]2 catalyst. Computationally, the high reactivities of the dnCOT and COD ligands are attributed to the steric repulsions that destabilize the Rh-product complex, the catalyst resting state in the catalytic cycle. The regioselectivities of reactions with various alkynes and different Rh catalysts are investigated, and a predictive model is provided that describes substrate-substrate and ligand-substrate steric repulsions, electronic effects, and noncovalent π/π and C-H/π interactions. In the reactions with dnCOT or COD ligands, the first new C-C bond is formed proximal to the bulky substituent on the alkyne to avoid ligand-substrate steric repulsions. This regioselectivity is reversed either by employing the smaller [Rh(CO)2Cl]2 catalyst to diminish the ligand-substrate repulsions or by using aryl alkynes, for which the ligand-substrate interactions become stabilizing due to π/π and C-H/π dispersion interactions. Electron-withdrawing groups on the alkyne prefer to be proximal to the first new C-C bond to maximize metal-substrate back-bonding interactions. These steric, electronic, and dispersion effects can all be utilized in designing new ligands to provide regiochem. control over product formation with high selectivities. The computational studies reveal the potential of employing the dnCOT family of ligands to achieve unique regiochem. control due to the steric influences and dispersion interactions assocd. with the rigid aryl substituents on the ligand.
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(j) Jiménez-Halla, J. O. C.; Kalek, M.; Stawinski, J.; Himo, F. Chem.—Eur. J. 2012, 18, 12424– 12436
Google Scholar
18j
Computational Study of the Mechanism and Selectivity of Palladium-Catalyzed Propargylic Substitution with Phosphorus Nucleophiles
Jimenez-Halla, J. Oscar C.; Kalek, Marcin; Stawinski, Jacek; Himo, Fahmi
Chemistry - A European Journal (2012), 18 (39), 12424-12436, S12424/1-S12424/155CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
The mechanism and sources of selectivity in the palladium-catalyzed propargylic substitution reaction that involves phosphorus nucleophiles, and which yields predominantly allenylphosphonates and related compds., have been studied computationally by d. functional theory. Full free-energy profiles are computed for both H-phosphonate and H-phosphonothioate substrates. The calcns. show that the special behavior of H-phosphonates among other heteroatom nucleophiles is indeed reflected in higher energy barriers for the attack on the central carbon atom of the allenyl/propargyl ligand relative to the ligand-exchange pathway, which leads to the exptl. obsd. products. It is argued that, to explain the preference of allenyl- vs. propargyl-phosphonate/phosphonothioate formation in reactions that involve H-phosphonates and H-phosphonothioates, anal. of the complete free-energy surfaces is necessary, because the product ratio is detd. by different transition states in the resp. branches of the catalytic cycle. In addn., these transition states change in going from a H-phosphonate to a H-phosphonothioate nucleophile.
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(k) Kalek, M.; Himo, F. J. Am. Chem. Soc. 2012, 134, 19159– 19169
Google Scholar
There is no corresponding record for this reference.
(l) Huang, G.; Xia, Y.; Sun, C.; Li, J.; Lee, D. J. Org. Chem. 2013, 78, 988– 995
Google Scholar
There is no corresponding record for this reference.
19
For selected reports of η³-allyl Rh species, see:
(a) Evans, P. A.; Lawler, M. J. J. Am. Chem. Soc. 2004, 126, 8642– 8643
Google Scholar
There is no corresponding record for this reference.
(b) Evans, P. A.; Leahy, D. K. Chemtracts 2003, 16, 567– 578
Google Scholar
There is no corresponding record for this reference.
(c) Evans, P. A.; Leahy, D. K.; Slieker, L. M. Tetrahedron: Asymmetry 2003, 14, 3613– 3618
Google Scholar
There is no corresponding record for this reference.
(d) Evans, P. A.; Robinson, J. E.; Moffett, K. K. Org. Lett. 2001, 3, 3269– 3271
Google Scholar
There is no corresponding record for this reference.
(e) Arnold, J. S.; Cizio, G. T.; Nguyen, H. M. Org. Lett. 2011, 13, 5576– 5579
Google Scholar
There is no corresponding record for this reference.
(f) Arnold, J. S.; Cizio, G. T.; Heitz, D. R.; Nguyen, H. M. Chem. Commun. 2012, 48, 11531– 11533
Google Scholar
There is no corresponding record for this reference.
(g) Arnold, J. S.; Stone, R. F.; Nguyen, H. M. Org. Lett. 2010, 12, 4580– 4583
Google Scholar
There is no corresponding record for this reference.
(h) Arnold, J. S.; Nguyen, H. M. J. Am. Chem. Soc. 2012, 134, 8380– 8383
Google Scholar
There is no corresponding record for this reference.
(i) Hayashi, T.; Okada, A.; Suzuka, T.; Kawatsura, M. Org. Lett. 2003, 5, 1713– 1715
Google Scholar
There is no corresponding record for this reference.
(j) Vrieze, D. C.; Hoge, G. S.; Hoerter, P. Z.; Van Haitsma, J. T.; Samas, B. M. Org. Lett. 2009, 11, 3140– 3142
Google Scholar
There is no corresponding record for this reference.
(k) Koschker, P.; Lumbroso, A.; Breit, B. J. Am. Chem. Soc. 2011, 133, 20746– 20749
Google Scholar
There is no corresponding record for this reference.
(l) Lumbroso, A.; Koschker, P.; Vautravers, N. R.; Breit, B. J. Am. Chem. Soc. 2011, 133, 2386– 2389
Google Scholar
19l
Redox-neutral atom-economic rhodium-catalyzed coupling of terminal alkynes with carboxylic acids toward branched allylic esters
Lumbroso, Alexandre; Koschker, Philipp; Vautravers, Nicolas R.; Breit, Bernhard
Journal of the American Chemical Society (2011), 133 (8), 2386-2389CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
A new method for the prepn. of a wide range of branched allylic esters from terminal alkynes that proceeds via a redox-neutral propargylic CH activation employing a rhodium(I)/DPEphos catalyst is reported.
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(m) Nishimura, T.; Hirabayashi, S.; Yasuhara, Y.; Hayashi, T. J. Am. Chem. Soc. 2006, 128, 2556– 2557
Google Scholar
There is no corresponding record for this reference.
(n) Choi, J.-c.; Osakada, K.; Yamamoto, T. Organometallics 1998, 17, 3044– 3050
Google Scholar
There is no corresponding record for this reference.
(o) Barros, H. J. V.; Guimarães, C. C.; dos Santos, E. N.; Gusevskaya, E. V. Organometallics 2007, 26, 2211– 2218
Google Scholar
There is no corresponding record for this reference.
(p) Jiao, L.; Lin, M.; Zhuo, L.-G.; Yu, Z.-X. Org. Lett. 2010, 12, 2528– 2531
Google Scholar
There is no corresponding record for this reference.
(q) Jiao, L.; Lin, M.; Yu, Z.-X. J. Am. Chem. Soc. 2011, 133, 447– 461
Google Scholar
There is no corresponding record for this reference.
(r) Lin, M.; Li, F.; Jiao, L.; Yu, Z.-X. J. Am. Chem. Soc. 2011, 133, 1690– 1693
Google Scholar
There is no corresponding record for this reference.
(s) Lin, M.; Kang, G.-Y.; Guo, Y.-A.; Yu, Z.-X. J. Am. Chem. Soc. 2012, 134, 398– 405
Google Scholar
There is no corresponding record for this reference.
(t) Li, Q.; Yu, Z.-X. Organometallics 2012, 31, 5185– 5195
Google Scholar
There is no corresponding record for this reference.
20
(a) Szabó, K. J. Chem.—Eur. J. 2004, 10, 5268– 5275
Google Scholar
20a
Palladium-catalyzed electrophilic allylation reactions via bis(allyl)palladium complexes and related intermediates
Szabo, Kalman J.
Chemistry - A European Journal (2004), 10 (21), 5268-5275CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. The synthetic scope of the allyl-Pd chem. can be extended to involve electrophilic reagents. The greatest challenge in these reactions is the catalytic generation of an allyl-Pd intermediate incorporating a nucleophilic allyl moiety. A vast majority of the published reactions that involve Pd-catalyzed allylation of electrophiles proceed via bis(allyl)palladium intermediates. The η1-moiety of the bis(allyl)palladium intermediates reacts with electrophiles, including aldehydes, imines, or Michael acceptors. Recently, catalytic electrophilic allylations via monoallylpalladium complexes have also been presented by employment of so-called pincer complex catalysts.
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(b) Szabó, K. J. Chem.—Eur. J. 2000, 6, 4413– 4421
Google Scholar
20b
Umpolung of the allylpalladium reactivity: mechanism and regioselectivity of the electrophilic attack on bis-allylpalladium complexes formed in palladium-catalyzed transformations
Szabo, Kalman J.
Chemistry - A European Journal (2000), 6 (23), 4413-4421CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH)
The structure and reactivity of various bis-allylpalladium complexes occurring as catalytic intermediates in important synthetic transformations were studied by applying d. functional theory at the B3PW91 (DA + P) level. η1,η3 Coordinated bis-allylpalladium complexes are readily formed from the corresponding η3,η3 complexes, esp. in the presence of π-acceptor phosphine ligands. The theor. calcns. indicate dσ → π* type hyperconjugative interactions occurring in the η1-coordinated allyl moiety of the η1,η3 coordinated complexes. These hyperconjugative interactions influence the structure of the complexes and dramatically increase the reactivity of the double bond in the η1-moiety. The DFT results indicate a remarkably low activation barrier for the electrophilic attack on the η1-allyl functionality. In bridged η1,η3 complexes, the electrophilic attack occurs with a very high regioselectivity, which can be explained from d-π type hyperconjugative interactions.
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21
There is an additional possibility of a migratory insertion of a third molecule of allene instead of the aldehyde. Such a pathway would eventually lead to [2 + 2 + 2] trimerization of the allene. However, since experimentally allene 2 only dimerizes (see ref 10), this possibility was not considered computationally.
There is no corresponding record for this reference.
22
For selected reviews of allylation of carbonyl compounds, see:
(a) Denmark, S. E.; Fu, J. Chem. Rev. 2003, 103, 2763– 2794
Google Scholar
22a
Catalytic enantioselective addition of allylic organometallic reagents to aldehydes and ketones
Denmark, Scott E.; Fu, Jiping
Chemical Reviews (Washington, DC, United States) (2003), 103 (8), 2763-2793CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review discusses the enantioselective allylation of aldehydes and ketones with a variety of allylmetal reagents to provide nonracemic homoallylic alcs. The mechanism of and chiral Lewis acid catalysts for the addn. of allylic silanes, stannanes and boranes to aldehydes and ketones, catalytic enantioselective allylation reactions with allylic halides, Lewis base-catalyzed enantioselective allylation with allylic trichlorosilanes, and allenylation and propargylation of aldehydes are discussed in the review; a table of conditions and selectivities for the enantioselective allylation of a variety of substrates is also provided.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXltVGjs78%253D&md5=b9f7c57ce56327693b6c8be57a50cda6
(b) Kennedy, J. W. J.; Hall, D. G. Angew. Chem., Int. Ed. 2003, 42, 4732– 4739
Google Scholar
22b
Recent advances in the activation of boron and silicon reagents for stereocontrolled allylation reactions
Kennedy, Jason W. J.; Hall, Dennis G.
Angewandte Chemie, International Edition (2003), 42 (39), 4732-4739CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. Despite the popularity of boron and silicon allylation reagents in stereocontrolled synthesis, they suffer from a no. of inherent limitations that have slowed down their development as synthetic tools for nucleophilic addns. to carbonyl compds. and imine derivs. These limitations are the low reactivity and diastereoselectivity of allyl trialkylsilane reagents, and the lack of catalytic systems for the activation and substoichiometric control of enantioselectivity in the addns. of allyl boron reagents. To develop more efficient and general methods for the control of abs. stereochem. in the resulting homoallylic alcs., new approaches aimed at solving the problem of activation of allylic boron and silicon reagents are needed. This Minireview describes a no. of recent approaches that have been devised to address this problem.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXosFKntLg%253D&md5=9661db0988639ab2c9ef7ab6b04e91b6
(c) Yu, C.-M.; Youn, J.; Jung, H.-K. Bull. Korean Chem. Soc. 2006, 27, 463– 472
Google Scholar
22c
Regulation of stereoselectivity and reactivity in inter- and intramolecular allylic transfer reactions
Yu, Chan-Mo; Youn, Jinsoup; Jung, Hee-Keum
Bulletin of the Korean Chemical Society (2006), 27 (4), 463-472CODEN: BKCSDE; ISSN:0253-2964. (Korean Chemical Society)
A review. The prepn. of enantiomerically enriched homoallylic alcs. through asym. addn. of chiral allylic transfer reagents and allylating reagents with chiral catalysts to carbonyl functionalities represents an important chem. transformation. Excellent progress has been made over the past decade in the development and application of catalytic asym. allylic transfer reactions. In this account, our efforts for the various intermol. allylic transfer reactions such as allylation, propargylation, allenylation, and dienylation utilizing an accelerating strategy and sequential allylic transfer reactions to achieve multiple stereoselection, mainly using transition metal catalysts, are described.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XkvVektr8%253D&md5=e940b908b85abcd16616c1858cef0085
(d) Marek, I.; Sklute, G. Chem. Commun. 2007, 1683– 1691
Google Scholar
22d
Creation of quaternary stereocenters in carbonyl allylation reactions
Marek, Ilan; Sklute, Genia
Chemical Communications (Cambridge, United Kingdom) (2007), (17), 1683-1691CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
A review. Despite the advances in stereoselective carbonyl allylation reactions, the creation of quaternary stereocenters by the addn. of 3,3'-disubstituted allylmetals to aldehydes is still a challenging issue. This feature article describes the most powerful approaches that have been devised to address this problem. The application of allyl boronates, allyl(trichloro)silanes and allylzinc reagents are discussed.
>> More from SciFinder ^®
https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXksFSit70%253D&md5=6f75de6048df9ee00d842748c108b870
(e) Hall, D. G. Synlett 2007, 1644– 1655
Google Scholar
There is no corresponding record for this reference.
23
For examples of [2 + 2 + 2] cyclization involving carbonyl compounds, see:
(a) Tsuchikama, K.; Yoshinami, Y.; Shibata, T. Synlett 2007, 1395– 1398
Google Scholar
There is no corresponding record for this reference.
(b) Tanaka, K.; Otake, Y.; Wada, A.; Noguchi, K.; Hirano, M. Org. Lett. 2007, 9, 2203– 2206
Google Scholar
There is no corresponding record for this reference.
24
Transition states connecting INT6 to INT7 and INT6′ to INT7′ could not be optimized. However, energy scans showed that the barriers are quite low, much lower than those for the direct reductive elimination (see the Supporting Information).
There is no corresponding record for this reference.
25
The methyl group in the η³-allyl complexes INT7 and INT7′, contrary to the case of INT2 discussed above, can undergo a relocation from the anti position to the syn position. This could potentially lead to the formation of isomers of products 4 and 6 containing different configurations at one of the double bonds. However, the barriers for the syn/anti substituent exchange in INT7 and INT7′ were calculated to be much higher than those for the reductive elimination. Therefore, INT7 and INT7′ undergo the reductive elimination before they can isomerize. See the Supporting Information for details.
There is no corresponding record for this reference.
26
The ratios were calculated using the Eyring equation. For example, the ratio of INT6 to INT6′ was calculated as
There is no corresponding record for this reference.
27
Wade, L. G., Jr. Organic Chemistry, 6th ed.; Prentice-Hall: Upper Saddle River, NJ, 2006.
Google Scholar
There is no corresponding record for this reference.
28
Nielsen, R. J.; Goddard, W. A., III. J. Am. Chem. Soc. 2006, 128, 9651– 9660
Google Scholar
There is no corresponding record for this reference.

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Abstract
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Scheme 1
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Scheme 2
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Scheme 3
Scheme 3. Possible General Mechanistic Pathways for the Reaction in Scheme 2b, As Suggested by Experimental Findings or Proposed in the Literature^a
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Scheme aEach of the three pathways can yield all of the possible products. Here, only the routes leading to product 3 are shown.
Figure 1
Figure 1. Free energy profiles for the possible initial steps of the reaction. The intermediates connecting INT1 with TS1 and TS1b were found to be higher in free energy than INT1, so they are not shown in the diagram (see the Supporting Information for details).
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Figure 2
Figure 2. Optimized structures of selected intermediates and transition states for the initial step (distances in Å and angles in deg). For clarity, the phenyl substituents on the phosphorus centers have been omitted in the figure.
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Scheme 4
Scheme 4. Possible Transition States for Oxidative Coupling of the Two Allene Moieties^a
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Scheme aIt should be noted that for each of the TS structures there are varying numbers of Z/E or cis/trans isomers, resulting in an overall total of 24 possible TSs.
Scheme 5
Scheme 5. Possible η³–η¹–η³ Isomerization of INT2^a
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Scheme aFree energies relative to the global zero are indicated in kcal/mol.
Figure 3
Figure 3. Free energy profile for the formation of the second C–C bond.
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Figure 4
Figure 4. Optimized structures of the allylation reactants, transition states, and resulting complexes.
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Figure 5
Figure 5. Free energy profile for the β-hydride elimination step.
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Figure 6
Figure 6. Optimized structures of the β-hydride elimination transition states and the resulting η¹-allyl complexes.
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Figure 7
Figure 7. Free energy profile for the reductive elimination step.
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Figure 8
Figure 8. Optimized structures of the reductive elimination reactants and transition states.
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Scheme 6
Scheme 6. Summary of the Mechanism of the [RhCl(dppe)]-Catalyzed 1:2 Coupling of Aldehydes and Allenes
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Figure 9
Figure 9. Free energy profile for the [RhCl(dppe)]-catalyzed 1:2 coupling of aldehydes and allenes.
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Scheme 7
Scheme 7. Summary of the Mechanism of the [Rh(dppe)]⁺-Catalyzed 1:2 Coupling of Aldehydes and Allenes
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Figure 10
Figure 10. Free energy profile for the [Rh(dppe)]⁺-catalyzed 1:2 coupling of aldehydes and allenes.
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Figure 11
Figure 11. Optimized structures of the alkoxide oxidation transition states TS6⁺ and TS6′⁺.
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References
This article references 28 other publications.
1. 1
  (a) Lautens, M.; Klute, W.; Tam, W. Chem. Rev. 1996, 96, 49– 92
  1a
  Transition Metal-Mediated Cycloaddition Reactions
  Lautens, Mark; Klute, Wolfgang; Tam, William
  Chemical Reviews (Washington, D. C.) (1996), 96 (1), 49-92CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
  A review with 226 refs. A discussion of established and interesting new cycloaddn. reactions promoted by metal species is presented.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XjsVKktw%253D%253D&md5=3776dd13a62c7dbef311a7cbf457dd7f
  (b) Kotha, S.; Brahmachary, E.; Lahiri, K. Eur. J. Org. Chem. 2005, 4741– 4767
  1b
  Transition metal-catalyzed [2+2+2] cycloaddition and application in organic synthesis
  Kotha, Sambasivarao; Brahmachary, Enugurthi; Lahiri, Kakali
  European Journal of Organic Chemistry (2005), (22), 4741-4767CODEN: EJOCFK; ISSN:1434-193X. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. The [2+2+2] cycloaddn. strategy is complementary to the well known Diels-Alder reaction for the generation of polycyclic compds. This [2+2+2] approach is atom-economical and, with the availability of new catalysts to effect the [2+2+2] cycloaddn. reaction, synthesis of a wide variety of highly functionalized polycycles is possible. This review deals with some recent advances relating to [2+2+2] cycloaddn. reactions involving the syntheses both of polycycles and of heterocycles. More specifically, syntheses of various biol. active mols., unusual amino acids, and theor. interesting mols. are described. An attempt has also been made to give an overview of recent advances in the achievement of chemo-, regio-, and stereoselectivity in cyclotrimerization reactions.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1KgurrM&md5=93220a4594f4dfa8e3cf02aac00ba43a
  (c) Murakami, M. Angew. Chem., Int. Ed. 2003, 42, 718– 720
  There is no corresponding record for this reference.
  (d) Inglesby, P. A.; Evans, P. A. Chem. Soc. Rev. 2010, 39, 2791– 2805
  1d
  Stereoselective transition metal-catalysed higher-order carbocyclisation reactions
  Inglesby, Phillip A.; Evans, P. Andrew
  Chemical Society Reviews (2010), 39 (8), 2791-2805CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
  A review. Transition metal-catalyzed higher-order carbocyclization reactions represent an important class of reactions due to their ability to construct complex polycyclic systems in a highly selective and atom-economical fashion. A key and striking feature with these transformations is the dichotomy in reactivity that a substrate displays with different transition metal complexes, which is akin to the manner enzymes direct terpene biosynthesis. This tutorial review details the historical development of higher-order carbocyclization reactions, specifically the variants of [m+2+2] that involve carbon-based π-systems, where m = 2, 3 and 4, in the context of crit. developments with various transition metal complexes.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptFyhu7c%253D&md5=f8e29c1b1b3795588b1be0f7e9c11a97
  (e) Shibata, T.; Tsuchikama, K. Org. Biomol. Chem. 2008, 6, 1317– 1323
  There is no corresponding record for this reference.
  (f) Tanaka, K. Chem.—Asian J. 2009, 4, 508– 518
  1f
  Transition-metal-catalyzed enantioselective [2+2+2] cycloadditions for the synthesis of axially chiral biaryls
  Tanaka, Ken
  Chemistry - An Asian Journal (2009), 4 (4), 508-518CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. Recent advances towards a development of novel transition-metal-catalyzed enantioselective [2+2+2] cycloaddn. for the synthesis of axially chiral biaryls are reviewed. A no. of efficient enantioselective biaryl syntheses were accomplished by chiral cobalt(I), iridium(I), and rhodium(I) complex catalyzed [2+2+2] cycloaddn. Furthermore, the enantioselective synthesis of axially chiral biaryls possessing non-biaryl axial chirality was also developed by using chiral rhodium(I) complexes as catalysts.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXks1Cht7c%253D&md5=941a1af8b94d4a5e67af5a6b0f552d64
  (g) Yu, Z.-X.; Wang, Y.; Wang, Y. Chem.—Asian J. 2010, 5, 1072– 1088
  1g
  Transition-metal-catalyzed cycloadditions for the synthesis of eight-membered carbocycles
  Yu, Zhi-Xiang; Wang, Yi; Wang, Yuanyuan
  Chemistry - An Asian Journal (2010), 5 (5), 1072-1088CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. Eight-membered carbocycles are in a wide variety of natural products that exhibit a broad range of biol. and medicinal activities (cf. the most potent anticancer drug, taxol). However, the synthesis of eight-membered carbocycles is quite challenging as traditional approaches are met with entropic and enthalpic penalties in the ring-forming transition states. These neg. effects can be totally or partially avoided with the implementation of transition-metal-catalyzed/mediated cycloaddns. In this focus review, examples of elegant and efficient metal-catalyzed and some metal-mediated cycloaddns. (including Ni- catalyzed [4+4] and Rh-catalyzed [4+2+2] and [5+2+1] reactions) are presented to illustrate this. Application of these cycloaddn. reactions in total synthesis was also presented to show the significance of these reactions in addressing challenges in natural product synthesis.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXls1Wkur8%253D&md5=867a869887dd578c5621f6992c3b6319
2. 2
  (a) Willis, M. C. Chem. Rev. 2010, 110, 725– 748
  2a
  Transition Metal Catalyzed Alkene and Alkyne Hydroacylation
  Willis, Michael C.
  Chemical Reviews (Washington, DC, United States) (2010), 110 (2), 725-748CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
  This review is a coordinated anal. of the intramol. or intermol. alkene hydroacylation using transition metal catalysts. The mechanism of such transformations is also presented in this systematic review.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtleisL3N&md5=bd9108b8b2ab0b60865cdd64044736fa
  (b) Jun, C.-H.; Moon, C. W.; Lee, D.-Y. Chem.—Eur. J. 2002, 8, 2422– 2428
  2b
  Chelation-assisted carbon-hydrogen and carbon-carbon bond activation by transition metal catalysts
  Jun, Chul-Ho; Moon, Choong Woon; Lee, Dae-Yon
  Chemistry - A European Journal (2002), 8 (11), 2422-2428CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH)
  A review with refs. on the chelation-assisted C-H and C-C bond activation of carbonyl compds. by RhI catalysts. Hydroacylation of olefins was accomplished by utilizing 2-amino-3-picoline as a chelation auxiliary. The same strategy was employed for the C-C bond activation of unstrained ketones. Allylamine 24 was devised as a synthon of formaldehyde. Hydroiminoacylation of alkynes with allylamine 24 was applied to the alkyne cleavage by the aid of cyclohexylamine.
  >> More from SciFinder ^®
  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XksFWgs7s%253D&md5=9f3fa5e5d3340dfb3541509a40f2bcc3
  (c) Leung, J. C.; Krische, M. J. Chem. Sci. 2012, 3, 2202– 2209
  2c
  Catalytic intermolecular hydroacylation of C-C π-bonds in the absence of chelation assistance
  Leung, Joyce C.; Krische, Michael J.
  Chemical Science (2012), 3 (7), 2202-2209CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
  A review. Intermol. rhodium catalyzed hydroacylation in the absence of chelation assistance remains a largely unmet challenge due to competing decarbonylation of the acylrhodium intermediates to form catalytically inactive carbonyl complexes. Here, catalytic systems for intermol. hydroacylation in the absence of chelation assistance are reviewed, with an emphasis on recently described processes that operate through mechanistic pathways beyond aldehyde C-H oxidative addn.
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3. 3
  (a) Jang, H.-Y.; Krische, M. J. Acc. Chem. Res. 2004, 37, 653– 661
  There is no corresponding record for this reference.
  (b) Ngai, M.-Y.; Kong, J.-R.; Krische, M. J. J. Org. Chem. 2007, 72, 1063– 1072
  There is no corresponding record for this reference.
  (c) Iida, H.; Krische, M. J. Top. Curr. Chem. 2007, 279, 77– 104
  There is no corresponding record for this reference.
  (d) Bower, J. F.; Kim, I. S.; Patman, R. L.; Krische, M. J. Angew. Chem., Int. Ed. 2009, 48, 34– 46
  There is no corresponding record for this reference.
  (e) Skucas, E.; Ngai, M.-Y.; Komanduri, V.; Krische, M. J. Acc. Chem. Res. 2007, 40, 1394– 1401
  There is no corresponding record for this reference.
4. 4
  Kong, J. R.; Krische, M. J. J. Am. Chem. Soc. 2006, 128, 16040– 16041
  4
  Catalytic Carbonyl Z-Dienylation via Multicomponent Reductive Coupling of Acetylene to Aldehydes and α-Ketoesters Mediated by Hydrogen: Carbonyl Insertion into Cationic Rhodacyclopentadienes
  Kong, Jong Rock; Krische, Michael J.
  Journal of the American Chemical Society (2006), 128 (50), 16040-16041CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Exposure of aldehydes or α-ketoesters to equal vols. of acetylene and hydrogen gas at ambient temp. and pressure in the presence of cationic rhodium catalysts provides products of carbonyl Z-butadienylation, which arise via multicomponent coupling of four mols.: two mols. of acetylene, a mol. of vicinal dicarbonyl compd., and a mol. of elemental hydrogen. The collective data suggest a catalytic mechanism involving carbonyl insertion into a cationic rhodacyclopentadiene intermediate derived via oxidative dimerization of acetylene. Hydrogenolytic cleavage of the resulting oxarhodacycloheptadiene via formal σ-bond metathesis provides the product of carbonyl addn. and cationic rhodium(I) to close the catalytic cycle. Studies involving the hydrogenation of 1,6-diyne 14a (I) in the presence of α-ketoester 6a (II) corroborate the proposed catalytic mechanism. These multicomponent couplings represent the first use of acetylene gas, a basic chem. feedstock, in metal-catalyzed reductive C-C bond formation.
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5. 5
  The reaction scope was later expanded by inclusion of other aldehydes and imines as coupling partners. See:
  (a) Skucas, E.; Kong, J. R.; Krische, M. J. J. Am. Chem. Soc. 2007, 129, 7242– 7243
  5a
  Enantioselective Reductive Coupling of Acetylene to N-Arylsulfonyl Imines via Rhodium Catalyzed C-C Bond-Forming Hydrogenation: (Z)-Dienyl Allylic Amines
  Skucas, Eduardas; Kong, Jong Rock; Krische, Michael J.
  Journal of the American Chemical Society (2007), 129 (23), 7242-7243CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The first highly enantioselective catalytic vinylation of aldimines to furnish allylic amines is reported. Exposure of arom. and aliph. N-arylsulfonyl aldimines to equal vols. of acetylene and hydrogen gas at 45 °C and ambient pressure in the presence of chirally modified cationic rhodium catalysts provides the (Z)-dienyl allylic amines, e.g., I, in highly optically enriched form (93-98% ee) and as single geometrical isomers (>95:5, Z/E). The coupling products arise via multicomponent coupling of four mols.: two mols. of acetylene, a mol. of aldimine, and elemental hydrogen. Unlike other imine addns. involving nonstabilized carbanions, the present protocol circumvents use of preformed organometallic reagents.
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  (b) Han, S. B.; Kong, J. R.; Krische, M. J. Org. Lett. 2008, 10, 4133– 4135
  There is no corresponding record for this reference.
6. 6
  Toyoshima, T.; Miura, T.; Murakami, M. Angew. Chem., Int. Ed. 2011, 50, 10436– 10439
  6
  Selective 1:2 Coupling of Aldehydes and Allenes with Control of Regiochemistry
  Toyoshima, Takeharu; Miura, Tomoya; Murakami, Masahiro
  Angewandte Chemie, International Edition (2011), 50 (44), 10436-10439, S10436/1-S10436/72CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A new rhodium-catalyzed coupling reaction of one mol. of aldehyde and two mol. of allene was developed and gave selectively either of two constitutional isomers of β,γ-dialkylidene ketones, e.g. I and II. Interestingly, the regioselectivity of the reaction depends on the counterion of a rhodium(I) complex.
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7. 7
  (a) Oonishi, Y.; Hosotani, A.; Sato, Y. J. Am. Chem. Soc. 2011, 133, 10386– 10389
  7a
  Rh(I)-Catalyzed Formal [6 + 2] Cycloaddition of 4-Allenals with Alkynes or Alkenes in a Tether
  Oonishi, Yoshihiro; Hosotani, Akihito; Sato, Yoshihiro
  Journal of the American Chemical Society (2011), 133 (27), 10386-10389CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Rh(I)-catalyzed formal [6 + 2] cycloaddn. of allenal, e.g., I, having an alkyne or alkene in a tether proceeded smoothly, giving fused bicyclic ketone derivs., e.g., II, in good to excellent yields. It was also found that cyclization of enantiomerically enriched I (94% ee) gave cyclic ketone deriv. II in high yield with reasonable chirality transfer (86% ee). This result indicates that this cyclization proceeds through stereoselective formation of rhodacycle H' followed by insertion of a multiple bond.
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  (b) Hojo, D.; Tanaka, K. Org. Lett. 2012, 14, 1492– 1495
  7b
  Rhodium-Catalyzed C-H Bond Activation/[4+2] Annulation/Aromatization Cascade To Produce Phenol, Naphthol, Phenanthrenol, and Triphenylenol Derivatives
  Hojo, Daiki; Tanaka, Ken
  Organic Letters (2012), 14 (6), 1492-1495CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  It has been established that a cationic rhodium(I)/dppp complex catalyzes the aldehyde C-H bond activation/[4 + 2] annulation/aromatization cascade to produce phenol, naphthol, phenanthrenol, and triphenylenol derivs. from readily available conjugated alkynyl aldehydes and alkynes.
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8. 8
  The total of 36 refers only to the number of possible linear compounds containing the reactant molecules coupled in a aldehyde–allene–allene sequence. In fact, two of the above isomers contain two asymmetric carbon atoms and hence can exist as two diastereomers, raising the number of possible products with distinct energies to 38. If cyclic structures and those containing allene–aldehyde–allene sequence are also considered, the number of possible products is even greater.
  There is no corresponding record for this reference.
9. 9
  Williams, V. M.; Kong, J. R.; Ko, B. J.; Mantri, Y.; Brodbelt, J. S.; Baik, M.-H.; Krische, M. J. J. Am. Chem. Soc. 2009, 131, 16054– 16062
  There is no corresponding record for this reference.
10. 10
  Miura, T.; Biyajima, T.; Toyoshima, T.; Murakami, M. Beilstein J. Org. Chem. 2011, 7, 578– 581
  10
  Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes
  Miura, Tomoya; Biyajima, Tsuneaki; Toyoshima, Takeharu; Murakami, Masahiro
  Beilstein Journal of Organic Chemistry (2011), 7 (), 578-581, No. 67CODEN: BJOCBH; ISSN:1860-5397. (Beilstein-Institut zur Foerderung der Chemischen Wissenschaften)
  A rhodium(I)/dppe catalyst promoted dimerization of monosubstituted allenes in a stereoselective manner to give cross-conjugated trienes, which are different from those obtained by a palladium catalyst. A palladium-catalyzed reaction of 1,2-undecadiene delivered the previously reported 11-methyl-10-methylene-8,11-eicosadiene and a new product [i.e., (8E)-10,11-bis(methylene)-8-eicosene]. [4+2] Cycloaddn. products of (8E)-10,11-bis(methylene)-8-eicosene with 1,1,2,2-ethenetetracarbonitrile and 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione were reported.
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11. 11
  In fact, to the best of our knowledge, all of the transition-metal-catalyzed [n + m + o] cycloadditions involving allenes developed to date incorporate only one or two molecules of allene into the product. See:
  (a) Murakami, M.; Ubukata, M.; Itami, K.; Ito, Y. Angew. Chem., Int. Ed. 1998, 37, 2248– 2250
  There is no corresponding record for this reference.
  (b) Shanmugasundaram, M.; Wu, M.-S.; Cheng, C.-H. Org. Lett. 2001, 3, 4233– 4236
  There is no corresponding record for this reference.
  (c) Shanmugasundaram, M.; Wu, M.-S.; Jeganmohan, M.; Huang, C.-W.; Cheng, C.-H. J. Org. Chem. 2002, 67, 7724– 7729
  There is no corresponding record for this reference.
  (d) Miura, T.; Morimoto, M.; Murakami, M. J. Am. Chem. Soc. 2010, 132, 15836– 15838
  There is no corresponding record for this reference.
  (e) Brusoe, A. T.; Alexanian, E. J. Angew. Chem., Int. Ed. 2011, 50, 6596– 6600
  There is no corresponding record for this reference.
12. 12
  (a) McCarren, P. R.; Liu, P.; Cheong, P. H.-Y.; Jamison, T. F.; Houk, K. N. J. Am. Chem. Soc. 2009, 131, 6654– 6655
  There is no corresponding record for this reference.
  (b) Liu, P.; McCarren, P.; Cheong, P. H.-Y.; Jamison, T. F.; Houk, K. N. J. Am. Chem. Soc. 2010, 132, 2050– 2057
  12b
  Origins of Regioselectivity and Alkene-Directing Effects in Nickel-Catalyzed Reductive Couplings of Alkynes and Aldehydes
  Liu, Peng; McCarren, Patrick; Cheong, Paul Ha-Yeon; Jamison, Timothy F.; Houk, K. N.
  Journal of the American Chemical Society (2010), 132 (6), 2050-2057CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The origins of reactivity and regioselectivity in nickel-catalyzed reductive coupling reactions of alkynes and aldehydes were investigated with d. functional calcns. The regioselectivities of reactions of simple alkynes are controlled by steric effects, while conjugated enynes and diynes are predicted to have increased reactivity and very high regioselectivities, placing alkenyl or alkynyl groups distal to the forming C-C bond. The reactions of enynes and diynes involve 1,4-attack of the Ni-carbonyl complex on the conjugated enyne or diyne. The consequences of these conclusions on reaction design are discussed.
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  (c) Liu, P.; Krische, M. J.; Houk, K. N. Chem.—Eur. J. 2011, 17, 4021– 4029
  12c
  Mechanism and Origins of Regio- and Enantioselectivities in RhI-Catalyzed Hydrogenative Couplings of 1,3-Diynes and Activated Carbonyl Partners: Intervention of a Cumulene Intermediate
  Liu, Peng; Krische, Michael J.; Houk, Kendall N.
  Chemistry - A European Journal (2011), 17 (14), 4021-4029, S4021/1-S4021/24CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
  The mechanism of the rhodium-catalyzed reductive coupling of 1,3-diynes and vicinal dicarbonyl compds. employing H2 as reductant was studied by d. functional theory. Oxidative coupling through 1,4-addn. of the RhI-bound dicarbonyl to the conjugated diyne via a seven-membered cyclic cumulene transition state leads to exclusive formation of linear adducts. Diyne 1,4-addn. is much faster than the 1,2-addn. to simple alkynes. The 1,2-dicarbonyl compd. is bound to rhodium in a bidentate fashion during the oxidative coupling event. The chemo-, regio-, and enantioselectivities of this reaction were studied and are attributed to this unique 1,4-addn. pathway. The close proximity of the ligand and the alkyne substituent distal to the forming C-C bond controls the regio- and enantioselectivity: coupling occurs at the sterically more demanding alkyne terminus, which minimizes nonbonded interaction with the ligand. A stereochem. model is proposed that accounts for preferential formation of the (R)-configurated coupling product when (R)-biaryl phosphine ligands are used.
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13. 13
  Frisch, M. J.; Gaussian 03, revision D.01; Gaussian, Inc.: Wallingford, CT, 2004.
  There is no corresponding record for this reference.
14. 14
  (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648– 5652
  14a
  Density-functional thermochemistry. III. The role of exact exchange
  Becke, Axel D.
  Journal of Chemical Physics (1993), 98 (7), 5648-52CODEN: JCPSA6; ISSN:0021-9606.
  Despite the remarkable thermochem. accuracy of Kohn-Sham d.-functional theories with gradient corrections for exchange-correlation, the author believes that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional (contg. local-spin-d., gradient, and exact-exchange terms) is tested for 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total at. energies of first- and second-row systems. This functional performs better than previous functionals with gradient corrections only, and fits expt. atomization energies with an impressively small av. abs. deviation of 2.4 kcal/mol.
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  (b) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785– 789
  14b
  Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
  Lee, Chengteh; Yang, Weitao; Parr, Robert G.
  Physical Review B: Condensed Matter and Materials Physics (1988), 37 (2), 785-9CODEN: PRBMDO; ISSN:0163-1829.
  A correlation-energy formula due to R. Colle and D. Salvetti (1975), in which the correlation energy d. is expressed in terms of the electron d. and a Laplacian of the 2nd-order Hartree-Fock d. matrix, is restated as a formula involving the d. and local kinetic-energy d. On insertion of gradient expansions for the local kinetic-energy d., d.-functional formulas for the correlation energy and correlation potential are then obtained. Through numerical calcns. on a no. of atoms, pos. ions, and mols., of both open- and closed-shell type, it is demonstrated that these formulas, like the original Colle-Salvetti formulas, give correlation energies within a few percent.
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15. 15
  Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270– 283
  15
  Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms scandium to mercury
  Hay, P. Jeffrey; Wadt, Willard R.
  Journal of Chemical Physics (1985), 82 (1), 270-83CODEN: JCPSA6; ISSN:0021-9606.
  Ab initio effective core potentials (ECP's) were generated to replace the Coulomb, exchange, and core-orthogonality effects of the chem. inert core electron in the transition metal atoms Sc to Hg. For the second and third transition series relative ECP's were generated which also incorporate the mass-velocity and Darwin relativistic effects into the potential. The ab initio ECP's should facilitate valence electron calcns. on mols. contg. transition-metal atoms with accuracies approaching all-electron calcns. at a fraction of the computational cost. Analytic fits to the potentials are presented for use in multicenter integral evaluation. Gaussian orbital valence basis sets are developed for the (3d,4s,4p), (4d,5s,5p), and (5d,6s,6p) orbitals of the first, second, and third transition series atoms, resp. All-electron and valence-electron at. excitation energies are also compared for the low-lying states of Sc-Hg, and the valence-electron calcns. reproduce the all-electron excitation energies (typically within a few tenths of an eV).
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16. 16
  (a) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995– 2001
  16a
  Quantum Calculation of Molecular Energies and Energy Gradients in Solution by a Conductor Solvent Model
  Barone, Vincenzo; Cossi, Maurizio
  Journal of Physical Chemistry A (1998), 102 (11), 1995-2001CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
  A new implementation of the conductor-like screening solvation model (COSMO) in the GAUSSIAN94 package is presented. It allows Hartree-Fock (HF), d. functional (DF) and post-HF energy, and HF and DF gradient calcns.: the cavities are modeled on the mol. shape, using recently optimized parameters, and both electrostatic and nonelectrostatic contributions to energies and gradients are considered. The calcd. solvation energies for 19 neutral mols. in water are found in very good agreement with exptl. data; the solvent-induced geometry relaxation is studied for some closed and open shell mols., at HF and DF levels. The computational times are very satisfying: the self-consistent energy evaluation needs a time 15-30% longer than the corresponding procedure in vacuo, whereas the calcn. of energy gradients is only 25% longer than in vacuo for medium size mols.
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  (b) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem. 2003, 24, 669– 681
  16b
  Energies, structures, and electronic properties of molecules in solution with the C-PCM solvation model
  Cossi, Maurizio; Rega, Nadia; Scalmani, Giovanni; Barone, Vincenzo
  Journal of Computational Chemistry (2003), 24 (6), 669-681CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
  The conductor-like solvation model, as developed in the framework of the polarizable continuum model (PCM), has been reformulated and newly implemented in order to compute energies, geometric structures, harmonic frequencies, and electronic properties in soln. for any chem. system that can be studied in vacuo. Particular attention is devoted to large systems requiring suitable iterative algorithms to compute the solvation charges: the fast multipole method (FMM) has been extensively used to ensure a linear scaling of the computational times with the size of the solute. A no. of test applications are presented to evaluate the performances of the method.
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17. 17
  Grimme, S. J. Comput. Chem. 2006, 27, 1787– 1799
  17
  Semiempirical GGA-type density functional constructed with a long-range dispersion correction
  Grimme, Stefan
  Journal of Computational Chemistry (2006), 27 (15), 1787-1799CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
  A new d. functional (DF) of the generalized gradient approxn. (GGA) type for general chem. applications termed B97-D is proposed. It is based on Becke's power-series ansatz from 1997 and is explicitly parameterized by including damped atom-pairwise dispersion corrections of the form C6·R-6. A general computational scheme for the parameters used in this correction has been established and parameters for elements up to xenon and a scaling factor for the dispersion part for several common d. functionals (BLYP, PBE, TPSS, B3LYP) are reported. The new functional is tested in comparison with other GGAs and the B3LYP hybrid functional on std. thermochem. benchmark sets, for 40 noncovalently bound complexes, including large stacked arom. mols. and group II element clusters, and for the computation of mol. geometries. Further cross-validation tests were performed for organometallic reactions and other difficult problems for std. functionals. In summary, it is found that B97-D belongs to one of the most accurate general purpose GGAs, reaching, for example for the G97/2 set of heat of formations, a mean abs. deviation of only 3.8 kcal mol-1. The performance for noncovalently bound systems including many pure van der Waals complexes is exceptionally good, reaching on the av. CCSD(T) accuracy. The basic strategy in the development to restrict the d. functional description to shorter electron correlation lengths scales and to describe situations with medium to large interat. distances by damped C6·R-6 terms seems to be very successful, as demonstrated for some notoriously difficult reactions. As an example, for the isomerization of larger branched to linear alkanes, B97-D is the only DF available that yields the right sign for the energy difference. From a practical point of view, the new functional seems to be quite robust and it is thus suggested as an efficient and accurate quantum chem. method for large systems where dispersion forces are of general importance.
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18. 18
  For instance, see:
  (a) Minenkov, Y.; Occhipinti, G.; Jensen, V. R. J. Phys. Chem. A 2009, 113, 11833– 11844
  There is no corresponding record for this reference.
  (b) Siegbahn, P. E. M.; Blomberg, M. R. A.; Chen, S.-L. J. Chem. Theory Comput. 2010, 6, 2040– 2044
  18b
  Significant van der Waals Effects in Transition Metal Complexes
  Siegbahn, Per E. M.; Blomberg, Margareta R. A.; Chen, Shi-Lu
  Journal of Chemical Theory and Computation (2010), 6 (7), 2040-2044CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
  There is, in general, very good experience using hybrid DFT to study mechanisms of enzyme reactions contg. transition metals. For redox reactions, the B3LYP* functional, which has 15% exact exchange, has been shown to be particularly accurate. Still, there are some cases which have turned out to be quite difficult with large errors. In the present study, the effects of van der Waals interaction have been investigated for these cases, using the empirical formula of Grimme. The results are encouraging.
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  (c) Harvey, J. N. Faraday Discuss. 2010, 145, 487– 505
  There is no corresponding record for this reference.
  (d) McMullin, C. L.; Jover, J.; Harvey, J. N.; Fey, N. Dalton Trans. 2010, 39, 10833– 10836
  18d
  Accurate modelling of Pd(0) + PhX oxidative addition kinetics
  McMullin, Claire L.; Jover, Jesus; Harvey, Jeremy N.; Fey, Natalie
  Dalton Transactions (2010), 39 (45), 10833-10836CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
  We have used dispersion-cor. DFT (DFT-D) together with solvation to examine possible mechanisms for reaction of PhX (X = Cl, Br, I) with Pd(PtBu3)2 and compare our results to recently published kinetic data (F. Barrios-Landeros, B. P. Carrow and J. F. Hartwig, J. Am. Chem. Soc., 2009, 131, 8141-8154). The calcd. activation free energies agree near-quant. with exptl. obsd. rate consts.
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  (e) Lonsdale, R.; Harvey, J. N.; Mulholland, A. J. J. Phys. Chem. Lett. 2010, 1, 3232– 3237
  18e
  Inclusion of Dispersion Effects Significantly Improves Accuracy of Calculated Reaction Barriers for Cytochrome P450 Catalyzed Reactions
  Lonsdale, Richard; Harvey, Jeremy N.; Mulholland, Adrian J.
  Journal of Physical Chemistry Letters (2010), 1 (21), 3232-3237CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  Prediction of cytochrome P 450 reactivity is of great importance to the development of new medicinal compds. D. functional theory (DFT) has proven itself as a useful tool in the characterization of the elusive reactive species, compd. I, and of the mechanisms of substrate oxidn. B3LYP is the most widely used d. functional in the study of P 450s; however, a major drawback of B3LYP is its inaccurate treatment of dispersion, leading to discrepancies between expt. and theory in some systems. Recent work has shown that an added empirical dispersion correction to B3LYP (B3LYP-D) yields more promising results for similar systems. In the present work, two previously studied systems, camphor hydroxylation and alkene oxidn., have been recalcd. using B3LYP-D. Our work shows that inclusion of dispersion has a significant effect on the energies and geometries of transition states and encounter complexes; furthermore, an improved agreement with exptl. data is obsd.
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  (f) Osuna, S.; Swart, M.; Solà, M. J. Phys. Chem. A 2011, 115, 3491– 3496
  There is no corresponding record for this reference.
  (g) Santoro, S.; Liao, R.-Z.; Himo, F. J. Org. Chem. 2011, 76, 9246– 9252
  There is no corresponding record for this reference.
  (h) Nordin, M.; Liao, R.-Z.; Ahlford, K.; Adolfsson, H.; Himo, F. ChemCatChem 2012, 4, 1095– 1104
  There is no corresponding record for this reference.
  (i) Xu, X.; Liu, P.; Lesser, A.; Sirois, L. E.; Wender, P. A.; Houk, K. N. J. Am. Chem. Soc. 2012, 134, 11012– 11025
  18i
  Ligand Effects on Rates and Regioselectivities of Rh(I)-Catalyzed (5 + 2) Cycloadditions: A Computational Study of Cyclooctadiene and Dinaphthocyclooctatetraene as Ligands
  Xu, Xiufang; Liu, Peng; Lesser, Adam; Sirois, Lauren E.; Wender, Paul A.; Houk, K. N.
  Journal of the American Chemical Society (2012), 134 (26), 11012-11025CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The first theor. study on the effects of ligands on the mechanism, reactivities, and regioselectivities of Rh(I)-catalyzed (5 + 2) cycloaddns. of vinylcyclopropanes (VCPs) and alkynes has been performed using d. functional theory (DFT) calcns. Highly efficient and selective intermol. (5 + 2) cycloaddns. of VCPs and alkynes have been achieved recently using two novel rhodium catalysts, [Rh(dnCOT)]+SbF6- and [Rh(COD)]+SbF6-, which provide superior reactivities and regioselectivities relative to that of the previously reported [Rh(CO)2Cl]2 catalyst. Computationally, the high reactivities of the dnCOT and COD ligands are attributed to the steric repulsions that destabilize the Rh-product complex, the catalyst resting state in the catalytic cycle. The regioselectivities of reactions with various alkynes and different Rh catalysts are investigated, and a predictive model is provided that describes substrate-substrate and ligand-substrate steric repulsions, electronic effects, and noncovalent π/π and C-H/π interactions. In the reactions with dnCOT or COD ligands, the first new C-C bond is formed proximal to the bulky substituent on the alkyne to avoid ligand-substrate steric repulsions. This regioselectivity is reversed either by employing the smaller [Rh(CO)2Cl]2 catalyst to diminish the ligand-substrate repulsions or by using aryl alkynes, for which the ligand-substrate interactions become stabilizing due to π/π and C-H/π dispersion interactions. Electron-withdrawing groups on the alkyne prefer to be proximal to the first new C-C bond to maximize metal-substrate back-bonding interactions. These steric, electronic, and dispersion effects can all be utilized in designing new ligands to provide regiochem. control over product formation with high selectivities. The computational studies reveal the potential of employing the dnCOT family of ligands to achieve unique regiochem. control due to the steric influences and dispersion interactions assocd. with the rigid aryl substituents on the ligand.
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  (j) Jiménez-Halla, J. O. C.; Kalek, M.; Stawinski, J.; Himo, F. Chem.—Eur. J. 2012, 18, 12424– 12436
  18j
  Computational Study of the Mechanism and Selectivity of Palladium-Catalyzed Propargylic Substitution with Phosphorus Nucleophiles
  Jimenez-Halla, J. Oscar C.; Kalek, Marcin; Stawinski, Jacek; Himo, Fahmi
  Chemistry - A European Journal (2012), 18 (39), 12424-12436, S12424/1-S12424/155CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
  The mechanism and sources of selectivity in the palladium-catalyzed propargylic substitution reaction that involves phosphorus nucleophiles, and which yields predominantly allenylphosphonates and related compds., have been studied computationally by d. functional theory. Full free-energy profiles are computed for both H-phosphonate and H-phosphonothioate substrates. The calcns. show that the special behavior of H-phosphonates among other heteroatom nucleophiles is indeed reflected in higher energy barriers for the attack on the central carbon atom of the allenyl/propargyl ligand relative to the ligand-exchange pathway, which leads to the exptl. obsd. products. It is argued that, to explain the preference of allenyl- vs. propargyl-phosphonate/phosphonothioate formation in reactions that involve H-phosphonates and H-phosphonothioates, anal. of the complete free-energy surfaces is necessary, because the product ratio is detd. by different transition states in the resp. branches of the catalytic cycle. In addn., these transition states change in going from a H-phosphonate to a H-phosphonothioate nucleophile.
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  (k) Kalek, M.; Himo, F. J. Am. Chem. Soc. 2012, 134, 19159– 19169
  There is no corresponding record for this reference.
  (l) Huang, G.; Xia, Y.; Sun, C.; Li, J.; Lee, D. J. Org. Chem. 2013, 78, 988– 995
  There is no corresponding record for this reference.
19. 19
  For selected reports of η³-allyl Rh species, see:
  (a) Evans, P. A.; Lawler, M. J. J. Am. Chem. Soc. 2004, 126, 8642– 8643
  There is no corresponding record for this reference.
  (b) Evans, P. A.; Leahy, D. K. Chemtracts 2003, 16, 567– 578
  There is no corresponding record for this reference.
  (c) Evans, P. A.; Leahy, D. K.; Slieker, L. M. Tetrahedron: Asymmetry 2003, 14, 3613– 3618
  There is no corresponding record for this reference.
  (d) Evans, P. A.; Robinson, J. E.; Moffett, K. K. Org. Lett. 2001, 3, 3269– 3271
  There is no corresponding record for this reference.
  (e) Arnold, J. S.; Cizio, G. T.; Nguyen, H. M. Org. Lett. 2011, 13, 5576– 5579
  There is no corresponding record for this reference.
  (f) Arnold, J. S.; Cizio, G. T.; Heitz, D. R.; Nguyen, H. M. Chem. Commun. 2012, 48, 11531– 11533
  There is no corresponding record for this reference.
  (g) Arnold, J. S.; Stone, R. F.; Nguyen, H. M. Org. Lett. 2010, 12, 4580– 4583
  There is no corresponding record for this reference.
  (h) Arnold, J. S.; Nguyen, H. M. J. Am. Chem. Soc. 2012, 134, 8380– 8383
  There is no corresponding record for this reference.
  (i) Hayashi, T.; Okada, A.; Suzuka, T.; Kawatsura, M. Org. Lett. 2003, 5, 1713– 1715
  There is no corresponding record for this reference.
  (j) Vrieze, D. C.; Hoge, G. S.; Hoerter, P. Z.; Van Haitsma, J. T.; Samas, B. M. Org. Lett. 2009, 11, 3140– 3142
  There is no corresponding record for this reference.
  (k) Koschker, P.; Lumbroso, A.; Breit, B. J. Am. Chem. Soc. 2011, 133, 20746– 20749
  There is no corresponding record for this reference.
  (l) Lumbroso, A.; Koschker, P.; Vautravers, N. R.; Breit, B. J. Am. Chem. Soc. 2011, 133, 2386– 2389
  19l
  Redox-neutral atom-economic rhodium-catalyzed coupling of terminal alkynes with carboxylic acids toward branched allylic esters
  Lumbroso, Alexandre; Koschker, Philipp; Vautravers, Nicolas R.; Breit, Bernhard
  Journal of the American Chemical Society (2011), 133 (8), 2386-2389CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  A new method for the prepn. of a wide range of branched allylic esters from terminal alkynes that proceeds via a redox-neutral propargylic CH activation employing a rhodium(I)/DPEphos catalyst is reported.
  >> More from SciFinder ^®
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  (m) Nishimura, T.; Hirabayashi, S.; Yasuhara, Y.; Hayashi, T. J. Am. Chem. Soc. 2006, 128, 2556– 2557
  There is no corresponding record for this reference.
  (n) Choi, J.-c.; Osakada, K.; Yamamoto, T. Organometallics 1998, 17, 3044– 3050
  There is no corresponding record for this reference.
  (o) Barros, H. J. V.; Guimarães, C. C.; dos Santos, E. N.; Gusevskaya, E. V. Organometallics 2007, 26, 2211– 2218
  There is no corresponding record for this reference.
  (p) Jiao, L.; Lin, M.; Zhuo, L.-G.; Yu, Z.-X. Org. Lett. 2010, 12, 2528– 2531
  There is no corresponding record for this reference.
  (q) Jiao, L.; Lin, M.; Yu, Z.-X. J. Am. Chem. Soc. 2011, 133, 447– 461
  There is no corresponding record for this reference.
  (r) Lin, M.; Li, F.; Jiao, L.; Yu, Z.-X. J. Am. Chem. Soc. 2011, 133, 1690– 1693
  There is no corresponding record for this reference.
  (s) Lin, M.; Kang, G.-Y.; Guo, Y.-A.; Yu, Z.-X. J. Am. Chem. Soc. 2012, 134, 398– 405
  There is no corresponding record for this reference.
  (t) Li, Q.; Yu, Z.-X. Organometallics 2012, 31, 5185– 5195
  There is no corresponding record for this reference.
20. 20
  (a) Szabó, K. J. Chem.—Eur. J. 2004, 10, 5268– 5275
  20a
  Palladium-catalyzed electrophilic allylation reactions via bis(allyl)palladium complexes and related intermediates
  Szabo, Kalman J.
  Chemistry - A European Journal (2004), 10 (21), 5268-5275CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. The synthetic scope of the allyl-Pd chem. can be extended to involve electrophilic reagents. The greatest challenge in these reactions is the catalytic generation of an allyl-Pd intermediate incorporating a nucleophilic allyl moiety. A vast majority of the published reactions that involve Pd-catalyzed allylation of electrophiles proceed via bis(allyl)palladium intermediates. The η1-moiety of the bis(allyl)palladium intermediates reacts with electrophiles, including aldehydes, imines, or Michael acceptors. Recently, catalytic electrophilic allylations via monoallylpalladium complexes have also been presented by employment of so-called pincer complex catalysts.
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  (b) Szabó, K. J. Chem.—Eur. J. 2000, 6, 4413– 4421
  20b
  Umpolung of the allylpalladium reactivity: mechanism and regioselectivity of the electrophilic attack on bis-allylpalladium complexes formed in palladium-catalyzed transformations
  Szabo, Kalman J.
  Chemistry - A European Journal (2000), 6 (23), 4413-4421CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH)
  The structure and reactivity of various bis-allylpalladium complexes occurring as catalytic intermediates in important synthetic transformations were studied by applying d. functional theory at the B3PW91 (DA + P) level. η1,η3 Coordinated bis-allylpalladium complexes are readily formed from the corresponding η3,η3 complexes, esp. in the presence of π-acceptor phosphine ligands. The theor. calcns. indicate dσ → π* type hyperconjugative interactions occurring in the η1-coordinated allyl moiety of the η1,η3 coordinated complexes. These hyperconjugative interactions influence the structure of the complexes and dramatically increase the reactivity of the double bond in the η1-moiety. The DFT results indicate a remarkably low activation barrier for the electrophilic attack on the η1-allyl functionality. In bridged η1,η3 complexes, the electrophilic attack occurs with a very high regioselectivity, which can be explained from d-π type hyperconjugative interactions.
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21. 21
  There is an additional possibility of a migratory insertion of a third molecule of allene instead of the aldehyde. Such a pathway would eventually lead to [2 + 2 + 2] trimerization of the allene. However, since experimentally allene 2 only dimerizes (see ref 10), this possibility was not considered computationally.
  There is no corresponding record for this reference.
22. 22
  For selected reviews of allylation of carbonyl compounds, see:
  (a) Denmark, S. E.; Fu, J. Chem. Rev. 2003, 103, 2763– 2794
  22a
  Catalytic enantioselective addition of allylic organometallic reagents to aldehydes and ketones
  Denmark, Scott E.; Fu, Jiping
  Chemical Reviews (Washington, DC, United States) (2003), 103 (8), 2763-2793CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
  A review discusses the enantioselective allylation of aldehydes and ketones with a variety of allylmetal reagents to provide nonracemic homoallylic alcs. The mechanism of and chiral Lewis acid catalysts for the addn. of allylic silanes, stannanes and boranes to aldehydes and ketones, catalytic enantioselective allylation reactions with allylic halides, Lewis base-catalyzed enantioselective allylation with allylic trichlorosilanes, and allenylation and propargylation of aldehydes are discussed in the review; a table of conditions and selectivities for the enantioselective allylation of a variety of substrates is also provided.
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  (b) Kennedy, J. W. J.; Hall, D. G. Angew. Chem., Int. Ed. 2003, 42, 4732– 4739
  22b
  Recent advances in the activation of boron and silicon reagents for stereocontrolled allylation reactions
  Kennedy, Jason W. J.; Hall, Dennis G.
  Angewandte Chemie, International Edition (2003), 42 (39), 4732-4739CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. Despite the popularity of boron and silicon allylation reagents in stereocontrolled synthesis, they suffer from a no. of inherent limitations that have slowed down their development as synthetic tools for nucleophilic addns. to carbonyl compds. and imine derivs. These limitations are the low reactivity and diastereoselectivity of allyl trialkylsilane reagents, and the lack of catalytic systems for the activation and substoichiometric control of enantioselectivity in the addns. of allyl boron reagents. To develop more efficient and general methods for the control of abs. stereochem. in the resulting homoallylic alcs., new approaches aimed at solving the problem of activation of allylic boron and silicon reagents are needed. This Minireview describes a no. of recent approaches that have been devised to address this problem.
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  (c) Yu, C.-M.; Youn, J.; Jung, H.-K. Bull. Korean Chem. Soc. 2006, 27, 463– 472
  22c
  Regulation of stereoselectivity and reactivity in inter- and intramolecular allylic transfer reactions
  Yu, Chan-Mo; Youn, Jinsoup; Jung, Hee-Keum
  Bulletin of the Korean Chemical Society (2006), 27 (4), 463-472CODEN: BKCSDE; ISSN:0253-2964. (Korean Chemical Society)
  A review. The prepn. of enantiomerically enriched homoallylic alcs. through asym. addn. of chiral allylic transfer reagents and allylating reagents with chiral catalysts to carbonyl functionalities represents an important chem. transformation. Excellent progress has been made over the past decade in the development and application of catalytic asym. allylic transfer reactions. In this account, our efforts for the various intermol. allylic transfer reactions such as allylation, propargylation, allenylation, and dienylation utilizing an accelerating strategy and sequential allylic transfer reactions to achieve multiple stereoselection, mainly using transition metal catalysts, are described.
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  (d) Marek, I.; Sklute, G. Chem. Commun. 2007, 1683– 1691
  22d
  Creation of quaternary stereocenters in carbonyl allylation reactions
  Marek, Ilan; Sklute, Genia
  Chemical Communications (Cambridge, United Kingdom) (2007), (17), 1683-1691CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
  A review. Despite the advances in stereoselective carbonyl allylation reactions, the creation of quaternary stereocenters by the addn. of 3,3'-disubstituted allylmetals to aldehydes is still a challenging issue. This feature article describes the most powerful approaches that have been devised to address this problem. The application of allyl boronates, allyl(trichloro)silanes and allylzinc reagents are discussed.
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  (e) Hall, D. G. Synlett 2007, 1644– 1655
  There is no corresponding record for this reference.
23. 23
  For examples of [2 + 2 + 2] cyclization involving carbonyl compounds, see:
  (a) Tsuchikama, K.; Yoshinami, Y.; Shibata, T. Synlett 2007, 1395– 1398
  There is no corresponding record for this reference.
  (b) Tanaka, K.; Otake, Y.; Wada, A.; Noguchi, K.; Hirano, M. Org. Lett. 2007, 9, 2203– 2206
  There is no corresponding record for this reference.
24. 24
  Transition states connecting INT6 to INT7 and INT6′ to INT7′ could not be optimized. However, energy scans showed that the barriers are quite low, much lower than those for the direct reductive elimination (see the Supporting Information).
  There is no corresponding record for this reference.
25. 25
  The methyl group in the η³-allyl complexes INT7 and INT7′, contrary to the case of INT2 discussed above, can undergo a relocation from the anti position to the syn position. This could potentially lead to the formation of isomers of products 4 and 6 containing different configurations at one of the double bonds. However, the barriers for the syn/anti substituent exchange in INT7 and INT7′ were calculated to be much higher than those for the reductive elimination. Therefore, INT7 and INT7′ undergo the reductive elimination before they can isomerize. See the Supporting Information for details.
  There is no corresponding record for this reference.
26. 26
  The ratios were calculated using the Eyring equation. For example, the ratio of INT6 to INT6′ was calculated as
  There is no corresponding record for this reference.
27. 27
  Wade, L. G., Jr. Organic Chemistry, 6th ed.; Prentice-Hall: Upper Saddle River, NJ, 2006.
  There is no corresponding record for this reference.
28. 28
  Nielsen, R. J.; Goddard, W. A., III. J. Am. Chem. Soc. 2006, 128, 9651– 9660
  There is no corresponding record for this reference.
Supporting Information
Supporting Information
Complete ref 13, additional results not shown in the text, and Cartesian coordinates of all optimized structures discussed in the paper. This material is available free of charge via the Internet at http://pubs.acs.org.
- ja4014166_si_001.pdf (8.97 MB)
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Mechanism and Selectivity of Rhodium-Catalyzed 1:2 Coupling of Aldehydes and AllenesClick to copy article linkArticle link copied!

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Abstract

1 Introduction

Scheme 1

Scheme 2

Scheme 3

2 Computational Details

3 Results and Discussion

3.1 Initial Step of the Catalytic Cycle: Oxidative Coupling versus Oxidative Addition

Figure 1

Figure 2

Scheme 4

Scheme 5

3.2 Formation of the Second C–C Bond

Figure 3

Figure 4

3.3 β-Hydride Elimination

Figure 5

Figure 6

3.4 Reductive Elimination

Figure 7

Figure 8

3.5 Overall Catalytic Cycle and Origins of the Regioselectivity in the [RhCl(dppe)]-Catalyzed Reaction

Scheme 6

Figure 9

3.6 Regioselectivity in the [Rh(dppe)]+-Catalyzed Reaction

Scheme 7

Figure 10

Figure 11

4 Conclusions

Supporting Information

Terms & Conditions

Author Information

Acknowledgment

References

Cited By

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Abstract

Scheme 1

Scheme 2

Scheme 3

Figure 1

Figure 2

Scheme 4

Scheme 5

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Scheme 6

Figure 9

Scheme 7

Figure 10

Figure 11

References

Supporting Information

Supporting Information

Terms & Conditions

Mechanism and Selectivity of Rhodium-Catalyzed 1:2 Coupling of Aldehydes and Allenes
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3.6 Regioselectivity in the [Rh(dppe)]⁺-Catalyzed Reaction