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Research ArticleMay 31, 2019

Primary Benzylamines by Efficient N-Alkylation of Benzyl Alcohols Using Commercial Ni Catalysts and Easy-to-Handle Ammonia Sources
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Yongzhuang Liu
Yongzhuang Liu
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Key Laboratory of Bio-Based Material Science and Technology, Ministry of Education, Northeast Forestry University, Harbin 150040, People’s Republic of China
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Anastasiia Afanasenko
Anastasiia Afanasenko
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Saravanakumar Elangovan
Saravanakumar Elangovan
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Zhuohua Sun
Zhuohua Sun
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Katalin Barta*
Katalin Barta
Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
*E-mail: [email protected]
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http://orcid.org/0000-0002-8046-4248

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ACS Sustainable Chemistry & Engineering

Cite this: ACS Sustainable Chem. Eng. 2019, 7, 13, 11267–11274

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https://doi.org/10.1021/acssuschemeng.9b00619

Published May 31, 2019

Abstract

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Primary benzylamines are highly important building blocks in the pharmaceutical and polymer industry. An attractive catalytic approach to access these compounds is the direct coupling of benzyl alcohols with ammonia via the borrowing hydrogen methodology. However, this approach is usually hampered by a series of side-reactions, one of the most prominent being the overalkylation of the formed primary amine. Herein, we describe a robust catalytic methodology, which utilizes commercially available heterogeneous Ni catalysts and easy-to-handle ammonia sources, such as aqueous ammonia or ammonium salts, for the formation of primary benzylamines with good selectivity and scope. Notably, our method enables the conversion of potentially lignin-derived vanillyl alcohol to vanillylamine, which can be used to produce emerging biobased polymers or as pharma building blocks. Important sugar derived platform alcohols as well as long chain aliphatic primary alcohols can be successfully aminated. Moreover, we provide an alternative, sustainable route to p-xylylenediamine and m-xylylenediamine, important components of heat resistant polyamides such as Kevlar.

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Keywords

Synopsis

Production of primary benzylamines and biobased amine building blocks with commercially available Ni catalysts and easily handled ammonia sources is accoplished via a hydrogen borrowing methodology.

Introduction

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Primary benzylamines are crucially important building blocks in the chemical industry. They are omnipresent moieties in biologically active compounds (1,2) and prominent scaffolds in widely used polymers, (3,4) thus the development of sustainable pathways to gain access to these compounds from readily available, inexpensive starting materials is of high importance. Especially primary benzylamines are important building blocks for further derivatization in the pharmaceutical or polymer industry. (3) Generally, these are obtained through the reaction of benzyl chloride with NH₃, a process that generates stoichiometric amounts of chloride salts as byproducts. (5,6)

A highly attractive and more environmentally friendly approach to generate the desired benzylamines would be to couple benzyl alcohols with the inexpensive and widely available ammonia, directly. This can be accomplished through the borrowing hydrogen methodology, which is atom-economic and waste-free and requires careful design or selection of an appropriate catalyst system capable to transfer hydrogen equivalents from the alcohol substrates to the corresponding imine intermediate to form the desired amine product. (7−12)

Surprisingly, despite their clear importance, only a few reports addressed the formation of primary benzylamines by the direct coupling of ammonia with benzyl alcohols using homogeneous (13−15) or heterogeneous (14−17) catalytic systems. This could be attributed to the fact that obtaining primary benzylamines in high selectivity has proven to be very challenging due to side reactions such as overalkylation of the formed primary amine product. (7,8)

The pioneering works of Shimizu have described a few examples of primary benzylamine synthesis from alcohols and ammonia gas, employing Ni/Al₂O₃ and CaSiO₃ as catalysts. (16,17) Shi reported the catalytic activity of NiCuFeO_x adopted for the alkylation of NH₃. (18) More recently, Hii obtained primary benzylamines using commercially available Ni/Al₂O₃–SiO₂ and ammonia gas in a continuous flow setup. (19) On the basis of these excellent works, we aimed at the development of new catalyst systems for the amination of important and not yet addressed substrates, primarily those that could be derived from various renewable resources. Thus, herein we specifically describe the chemistry of lignin-derived vanillyl alcohol (20) for the first time and demonstrate the challenging conversion of this renewable building block. The product benzylamine can be used, among others, for the production of emerging biobased polymers. (3,4) Our method also allows access to sugar-derived biobased target compounds, such as furfurylamine, 5-methylfurfurylamine, and tetrahydrofurfurylamine as well as aliphatic primary amines. Moreover, we also present sustainable pathways to access p-xylylenediamine and m-xylylenediamine that are important precursors for the production of thermally stable polyamide fibers such as Kevlar. (21)

Experimental Section

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Materials

Benzyl alcohol and its derivatives; dodecane; Raney nickel catalysts 2800, 3420, and 4200; Ni/Al₂O₃–SiO₂; aqueous ammonia (aq. NH₃, 25 wt %); ammonia in THF (0.4 M); ammonia in dioxane (0.5 M); ammonia carbonate; and all the solvents were purchased from Sigma-Aldrich and used as received. Carbon supported nickel (Ni/C, 10% Ni loading) catalyst was purchased from Riogen, Inc.

Methods

Representative Procedures

General Procedure 1

A 10 mL Swagelok stainless steel microreactor, equipped with a stirring bar, was charged with substrate (1 mmol), 200 mg of catalysts (as specified), 0.4 mL of aq. NH₃ (25%, 5.2 mmol), and 20 μL of dodecane (0.088 mmol) as an internal standard. Then, the reactor was sealed and placed in a preheated aluminum heating block at appropriate temperature (typically 180 °C). After the indicated reaction time (typically 18 h), the microreactor was cooled down to room temperature using an ice–water bath. The crude mixture (a solution) was separated from the metal Ni using a magnet and analyzed by GC-FID directly; conversion and selectivity were calculated based on calibration curves and an internal standard as shown in the Supporting Information, page S3. Then, the product was isolated as HCl salt as described next. The solvent was evaporated under reduced pressure, and diethyl ether (25 mL) was added. After drying over MgSO₄, the mixture was filtered and washed with an extra 10 mL of diethyl ether, then 0.5 mL of 1 M HCl in diethyl ether was added. A precipitate was formed immediately; the HCl salt was isolated by filtration and eventually washed with diethyl ether.

General Procedure 2

A 10 mL Swagelok stainless steel microreactor, equipped with a stirring bar, was charged with substrate (vanillyl alcohol, 0.5 mmol), 200 mg of catalysts (as specified), and ammonia carbonate (2 mmol). Then, the reactor was sealed and placed in a preheated aluminum heating block at an appropriate temperature (typically 140 °C). After the indicated reaction time (typically 18 h), the microreactor was cooled down to room temperature using an ice–water bath. The crude mixture was separated from the catalyst by filtration, concentrated in vacuo, and analyzed by GC-FID. The residue was purified by flash column chromatography to provide the pure amine product.

Control Reaction and Leaching Test

Control experiments were performed under general procedure 1 in the absence of catalyst in the Swagelok reactor. The obtained results displayed no formation of any amine product. In order to establish if leached Ni could have contributed to the reaction: two kinds of experiments were conducted, namely, “hot filtration” as well as ICP analysis for both catalytic systems (Raney Ni with aqueous ammonia and Ni/Al₂O₃–SiO₂ with ammonium carbonate). (22,23) The results revealed no product formation for both Raney Ni and Ni/Al₂O₃–SiO₂ systems (Supporting Information, pages S3 and S4).

Results and Discussion

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With the aim to establish a novel methodology that could be further easily extended to more complex compounds, such as lignin-derived vanillyl alcohol as well as carbohydrate derived alcohols (Figure 1a) for the direct amination of alcohols to primary amines with aqueous ammonia (aq. NH₃) instead of ammonia gas, via the borrowing hydrogen methodology (Figure 1b), we have selected simple benzyl alcohol (1a) as a suitable model compound (Scheme 1).

Figure 1. (a) Possible biobased amine building blocks from lignocellulose. (b) General mechanism of the “hydrogen borrowing” strategy. (c) Representative examples of bioactive molecules comprising benzylamine moieties or furfurylamine.

Scheme 1. Possible Reaction Pathways during Direct Amination of Benzyl Alcohol with Ammonia Using Raney Ni As Hydrogen Transfer Catalyst

Given the early examples of using Ni catalysts in borrowing hydrogen-based alkylation of amines, (16,17,19) we have evaluated commercially available Ni/C, Ni/Al₂O₃–SiO₂, and Raney Ni catalysts for the primary amine synthesis from benzyl alcohol and aq. NH₃. Using Ni/Al₂O₃–SiO₂ as a catalyst, full conversion was achieved, however only a trace amount of product was observed (Table S1) due to the formation of secondary amine as a major product. Raney Ni (92% conversion and 43% primary amine selectivity) was found more active than Ni/C (36% conversion), therefore we chose Raney Ni for further optimization and evaluated Raney Ni-3020, Raney Ni-4200, and Raney Ni-2800, which all displayed good conversion of 81–88% and varying selectivity values (41–61%). These results are summarized in Figure S1 and Table S2.

Reaction Network

On the basis of the products obtained thus far with Raney Ni (for a typical GC-FID chromatogram, see Figure S2), a reaction network was constructed that is summarized in Scheme 1. The main, desired pathway proceeds through benzyl alcohol (1a) dehydrogenation, followed by imine (2′a) formation and reduction using the H₂ equivalent “borrowed” from the alcohol. Given the increased nucleophilicity of the primary amine (2a) product compared to ammonia, formation of N-benzylidenebenzylamine (3′a) and the corresponding dibenzylamine (3a) is a dominant side reaction. Interestingly, under these reaction conditions, hydrogenolysis of benzyl alcohol to toluene (4a) and decarbonylation of the benzaldehyde intermediate to benzene (5a) cannot be prevented.

Optimization of the Reaction Conditions

On the basis of the reaction network (Scheme 1), it is clear that restraining the above-mentioned hydrogenolysis and double alkylation side reactions would promote selectivity toward the desired primary amine. Thus, the substrate/catalyst ratio, the nature of the reaction media, reaction time, and ammonia/substrate ratio were investigated, since especially a higher amount of ammonia would favor the formation of primary amine, and in this respect, ammonia solubility in the reaction medium would also play a role. Indeed, solvent screening using Raney Ni-2800 found large dependence of the product selectivity and substrate conversion on the type of solvent used (Table S3). Among the tested solvents, toluene, t-amyl alcohol, and p-xylene have shown good conversion (over 80%) and selectivity (50–60%) values. Due to the highest selectivity (61%) obtained therein, p-xylene, which can also be obtained from renewables, was chosen as an appropriate reaction medium.

After identifying p-xylene as a solvent of choice, next the substrate/catalyst ratio, reaction temperature, and reaction time were varied. The optimal amount of catalyst was found to be 200 mg, leading to a good conversion of 83% and selectivity of 61%. With further increasing the catalyst amount, almost full substrate conversion (97%) was achieved, however, hydrogenolysis and decarbonylation side reactions became more pronounced, resulting in benzene and toluene as main products (Figure 2a). Further, it was confirmed that the already used 180 °C is ideal for both conversion and primary amine selectivity than lower temperatures 160–170 °C (Figure 2c). Thus, the product formation profile in the function of reaction time was conducted at 180 °C; this revealed a gradual increase in conversion and selectivity from 2 to 18 h reaction time (Figure 2d). The above-mentioned product distributions related to reaction optimization can be found in Tables S4–S7.

Figure 2. Influence of various reaction parameters on the selectivity of primary benzylamines. Varying amounts of (a) catalyst (50–400 mg), (b) ammonia equivalents (1.3–7.8 mmol), (c) reaction temperatures (160–180 °C, 18 h), and (d) reaction time (180 °C, 2–24 h). General reaction conditions: *general procedure 1*, benzyl alcohol (1 mmol), aq. NH₃ (25 wt %), Raney Ni 2800, and dodecane (internal standard, 20 μL).

From the reaction network (Scheme 1), it is anticipated that a higher ammonia/substrate ratio would increase selectivity to the desired product (2a) since conversion of the aldehyde intermediate (1′a) to the corresponding imine (2′a) needs to compete with aldehyde decarbonylation. Furthermore, providing more ammonia should be beneficial for suppressing double alkylation side reactions as well. Thus, in order to boost selectivity to the desired product, we conducted a series of reactions with varying ammonia amounts (see Figure 2b and Table S5). Gratifyingly, the primary amine selectivity could further be increased to 74% using a 5-fold excess (5.2 mmol) of ammonia compared to the substrate, while still maintaining good conversion levels. Further, the pressure in the minireactor was evaluated by using a Parr reactor of identical volume and was found to be ∼14 bar. A detailed discussion related to this point can be found in the Supporting Information, page S5. Further increasing the amount of aqueous ammonia resulted in a slight drop in selectivity. We consider the water to play an important role in the reaction, which facilitates imine (2′a) hydrolysis to the corresponding aldehyde (1′a) and , thus, suppresses the formation of the undesired 2′a. (24) It was also observed that conversion levels consistently remained around 80% independently of the amount of ammonia, as expected. No obvious leaching was detected after reaction by ICP analysis (see Supporting Information page S4 and S5). The Ni content in the solution was 24 ppm, which is comparable with previous literature values. (19)

Catalyst Recycling and Reusability

The advantage of using Raney Ni as a catalyst is the ease of reusability due to its magnetic properties. Therefore, we have demonstrated a simple recycling procedure with the help of a magnet. After the first run, the catalyst was washed with the reaction solvent in the microreactor, and subsequently fresh substrate, internal standard, and aq. NH₃ were introduced to carry out the next reaction. With this method, the conversion and selectivity values were roughly maintained for eight cycles. The results are shown in Figure S3, and a detailed products distribution of each run is shown in Table S8. Interestingly, a good conversion of 65–70% and good selectivities of 63–78% were generally obtained. The formation of toluene and benzene side products was highest in the first run, which may be attributed to the small amount of hydrogen present in the catalyst itself.

Primary Benzylamines from Benzyl Alcohols

With the optimized reaction conditions in hand, we next established the scope of the method using benzyl alcohols bearing various electron withdrawing and electron donating substituents. The results are summarized in Table 1, and related experimental data are shown in Figures S8–S15. In general, conversion values and selectivities exceeded those obtained with unsubstituted benzyl alcohol. Benzyl alcohols 1b and 1c bearing an electron donating p-methyl and tert-butyl groups displayed ∼90% conversion and 56% and 70% isolated yields of 2b and 2c, respectively (entries 1 and 2). Using an o-methyl substituted benzyl alcohol 1d showed 44% isolated yield of o-methylbenzylamine 2d (entry 3). Good conversion and selectivity were obtained with p-fluorobenzyl alcohol 1e as a substrate (entry 4). However, the p-fluorobenzylamine 2e product was challenging to isolate. Poor results were obtained with the chlorinated substrate 1f (entry 5) likely due to substrate dehalogenation and catalyst poisoning. Piperonyl alcohol 1g delivered the corresponding pharmaceutically relevant primary amine 2g in good, 58% isolated yield (entry 6). Substrates bearing both p-trifluoromethyl 1h and m-trifluoromethyl 1i groups displayed around 50% isolated yields of corresponding primary amines (entries 7 and 8).

Table 1. Primary Amines via Coupling of Various Alcohols with aq. NH₃^b

^{^a}

Conversions and selectivities were determined by GC-FID.

^{^b}

General reaction conditions, general procedure 1: alcohol (1.0 mmol), aq. NH₃ (25 wt %, 0.4 mL), Raney Ni catalyst (200 mg), t-amyl alcohol (3 mL), 180 °C, 24 h, isolated yields using ammonia salt method in parentheses.

Moving toward lignin-related building blocks 1j–1l that have not been explored previously, we have found that the 3,4-methoxybenzyl alcohol 1k, as well as p-methoxy substituted benzyl alcohol 1j, showed excellent conversion (90%) and high selectivity values (entries 9 and 10). Interestingly, when using p-hydroxybenzyl alcohol 1l as a substrate (entry 11), no nitrogen containing products were observed as shown in Figure S4. The main detected products were 4-hydroxytoluene (80%), phenol (17%), and a trace amount of dimer, which could be attributed to known deoxygenative coupling with the formed phenol. (20,25)

Toward Biobased and Other Important Benzylamines

Vanillin is industrially produced from guaiacol by classic “bottom-up” strategies, and the current industrial demand for vanillin is not yet substantial. (26) However, a revived interest in lignin oxidation (27,28) methods applied on both organosolv and Kraft lignin led to an increase of obtainable well-defined building blocks: vanillin and syringaldehyde. As important aromatic platform chemicals, these aromatic monomers will, in the future, serve as starting material for the production of emerging biobased chemicals, polymers, and materials, creating more demand. Many of the target products will contain nitrogen, therefore both reductive amination from vanillin as well as the development of novel hydrogen borrowing methods starting directly from vanillin alcohol is of high importance. With a recent focus on lignin depolymerization, (4) both vanillyl and syringyl-alcohol may be, in the future, potentially obtainable directly from lignin or lignocellulose.

Phenolic primary amines are important building blocks for pharmaceuticals (29,30) and polymers (31) (Figure 1c). However, surprisingly, in the literature there is a lack of hydrogen borrowing methodologies applied to vanillyl alcohol, syringyl alcohol, or even the simpler p-hydroxybenzyl alcohol as a substrate using ammonia. In line with our ongoing interest in amination chemistry (32,33) and catalytic lignin depolymerization, (34) we sought to develop a new catalytic method for the efficient amination of the valuable biobased alcohols.

In our initial studies, we observed that vanillyl and syringyl alcohols, bearing a free phenol group, behaved markedly different from the structurally related and electronically similar 3,4-dimethoxybenzyl alcohol shown above (Table 1, entry 10). When we used vanillyl alcohols for the amination reaction with Raney Ni and ammonia at 180 °C, the results were similar to those obtained with p-hydroxybenzyl alcohol. The main product was 2-methoxy-4-methyl phenol (65%), suggesting that hydrogenolysis of the starting material was prevalent over dehydrogenation. Surprisingly, further decreasing the reaction temperature and screening various ammonia sources have not significantly influenced this tendency, and 2-methoxy-4-methylphenol remained the dominant product in all of the examined reactions. At the same time, due to the lower reaction temperature, also the decarbonylation product o-methoxyphenol appeared in significant quantities (Figure 3, Table S9).

Figure 3. Comparison study between Raney Ni (gray region) and Ni/Al₂O₃–SiO₂(white region) catalyzed vanillyl alcohol amination with various ammonia sources. General reaction conditions: *general procedure 2*, 200 mg of Ni catalyst, 0.5 mmol of substrate, 2 equiv of NH₃ in ammonia salts, 140 °C, 18 h; conversion and selectivity values were calculated by GC-FID. For aq. NH₃: 0.4 mL aq. NH₃, 3 mL t-amyl alcohol as solvent. For NH₃ in organic solvents: directly use 3 mL of ammonia in dioxane (0.5 M) or THF (0.4 M) as both solvent and ammonia source.

When examining the product suite obtained during the amination of vanillyl alcohol with ammonia (Figure S5), several differences were observed compared to the reactivity of regular benzyl alcohols, which did not contain a phenol substituent para to the benzyl alcohol moiety. Besides the higher tendency for hydrogenolysis, the formation of dimeric aromatics that did not contain any nitrogen were observed as side products. Indeed, the tendency for vanillyl alcohol to undergo various dimerization pathways (Figure 4), especially under basic conditions, involving a quinonemethide intermediate (Figure 4, compound 7m) is known from early works of Hemmingson and Leary (35) and Dimmel et al. (20) Based on the molecular weight and MS fragments of the byproducts and previous studies, (20,35) herein we propose possible formation pathways of the dimeric byproducts as shown in Figure 4 (a detailed discussion is shown in the Supporting Information, note 4). The ease of water or hydroxide release from these phenolic benzyl alcohols due to resonance stabilization should be the main reason for the prominent side reactions occurring in these substrates, rendering the direct amination that requires maintaining the C–O bond challenging.

Figure 4. Possible dimerization byproducts detected from amination reaction of vanillyl alcohol.

Due to the observed prominent hydrogenolysis activity of Raney Ni, we have decided to investigate the use of other Ni-based catalysts. We chose the commercially available Ni/Al₂O₃–SiO₂ catalyst and various ammonia sources for further screening (Figure 3 and Table S10). As before, in all cases, near full conversion was achieved, and (NH₄)₂CO₃ emerged as the best ammonia source, with a 45% yield of vanillylamine detected.

Therefore, further optimization was conducted with Ni/Al₂O₃–SiO₂ as a catalyst and (NH₄)₂CO₃ as an ammonia source. In particular, the catalyst to substrate and substrate to ammonia ratio was varied as specified in Table 2. It was concluded that a substrate to (NH₄)₂CO₃ ratio of 1:4 was optimal for achieving good primary amine selectivities and suppressing over alkylation pathways to a certain extent. For example, excellent conversion (>99%) and good (58%) selectivity of vanillylamine with 40% isolated product yield were obtained under specific conditions (Table 2, entry 4). It should be noted that the inherent dimerization pathways could not be suppressed under any of the selected conditions, presenting a general hurdle for achieving higher product selectivity under these conditions, however based on excellent prior work, conversion levels should be improvable in a flow setup. (19) A relatively high, 144 ppm Ni content was detected by ICP analysis, which could be attributed to the existence of the acidic phenol group (see Supporting Information pages S4, S5).

Table 2. Direct Synthesis of Primary Amines from Vanillyl Alcohol and (NH₄)₂CO₃ Using Ni/Al₂O₃–SiO₂ As a Catalyst^a

				selectivity/%
entry	catalyst amount/mg	sub. (mmol)/(NH₄)₂CO₃ (mmol) ratio	conversion /%	2m	5m	4m	6m	3′m	dimers
1	100	0.5:1	83	52	2	3	0	19	23
2	100	0.25:1	87	54	0	2	1	25	27
3	100	0.5:2	54	50	1	2	0	23	23
4	200	0.5:2	>99	58 (40)^b	2	4	0	16	20
5	50	0.5:2	34	56	1	2	0	19	22
6	400	1:4	>99	4	4	55	1	7	29

^{^a}

General reaction conditions: general procedure 2, Ni/Al₂O₃–SiO₂ catalyst, vanillyl alcohol substrate, (NH₄)₂CO₃, 3 mL t-amyl alcohol, 140 °C, 18 h; conversion and selectivity were calculated by GC-FID.

^{^b}

Isolated yield by column chromatography.

Other Biobased and Aliphatic Alcohols

Further, we applied our catalytic system to other valuable biobased alcohols (36) as well as challenging aliphatic alcohols (Table 3). The results revealed that significantly better yields of furfurylamine (2n,52%), 5-methylfurfurylamine (2o, 45%), and tetrahydrofurfurylamine (2p,41%) were obtained with Ni/Al₂O₃–SiO₂ compared to Raney Ni, which could be explained by the presence of hydrogen in Raney Ni favoring the hydrogenolysis of the corresponding alcohol. The aliphatic alcohols, namely cyclopentanol (1q), 1-octanol (1r), and 1-dodecanol (1s), were successfully converted to the corresponding primary amines with 34%, 41%, and 47% isolated yields, respectively. Gratifyingly, when the Ni/Al₂O₃–SiO₂ catalytic system was applied to isosorbide, the desired amine 2t was obtained with 51% yield.

Table 3. Primary Amines via Coupling of Bio-Based and Aliphatic Alcohols with aq. NH₃^c

^{^a}

Reaction temperature at 180 °C.

^{^b}

Isolated yields by ammonia salt method.

^{^c}

General reaction conditions: general procedure 1, alcohol (0.5 mmol), aq. NH₃ (25 wt %, 0.4 mL), Ni catalyst (200 mg), t-amyl alcohol (3 mL), 160 °C, 18 h; yields were determined by GC-FID.

Next, we turned our attention to another class of important benzylamines, p-xylylenediamine and m-xylylenediamine, that contains important polymer building blocks for the production of thermally stable polyamide fibers such as Kevlar. Industrially, these xylylenediamines are produced by ammoxidizing xylene to phthalonitrile (∼400 °C), followed by hydrogenation (100 bar H₂). (37) It is fair to mention that the latter step is highly selective and well-established, however, production of dicyanobenzenes usually requires quite harsh reaction conditions starting from xylene. If, in the future, the production of 1,4- benzenedimethanol becomes feasible from renewables, the direct amination of these alcohols with ammonia (provided selectivity and efficiency improves) will become a superior sustainable method of choice to produce these important diamines. Therefore, proof-of principle methods to accomplish this important direct amination step are highly desired.

To this end, we started our investigation using 1,4-benzenedimethanol (1u), aqueous NH₃, and Raney Ni at 180 °C as starting reaction conditions. However, the desired p-xylylenediamine (2u) was only produced in small quantities (Table 4, entry 1), and besides, full substrate conversion formation of benzylamine (50%) and p-methylbenzylamine (32%) was shown as two main products (Table S11). This clearly signified a fast hydrogenolysis under these conditions (180 °C) and an insufficient substrate/ammonia ratio. Indeed, much better p-xylylenediamine selectivity was seen when increasing the NH₃ amount. When the reaction temperature further decreased to 170 °C, a good product selectivity was achieved. Further reducing the reaction temperature to 160 °C resulted in a drop in substrate conversion. When using 1,3-benzenedimethanol as a substrate and the established reaction conditions, m-xylylenediamine 2v was obtained, albeit with slightly lower selectivity (Table 4, entry 5).

Table 4. Direct Synthesis of Xylylenediamines from Benzenedimethanols and aq. NH₃ Using Raney Ni As a Catalyst^c

^{^a}

3 mL t-amyl alcohol and 1 mL aq. NH₃ (25%).

^{^b}

0.5 mmol 1,3-benzenedimethanol as substrate; conversion and selectivity values were calculated by GC-FID.

^{^c}

General reaction conditions: general procedure 1, 200 mg Raney Ni catalyst, 0.5 mmol 1,4-benzenedimethanol substrate, 2 mL aq. NH₃ (25%), 2 mL t-amyl alcohol, 18 h.

Conclusion

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In summary, we have presented the direct amination of benzyl alcohols with NH₃ for obtaining a range of primary benzylamines, including examples potentially relevant for the pharmaceutical and polymer industry. The method could be extended to direct amination of aromatic diols, to access the important building blocks p-xylylenediamine and m-xylylenediamine. The conversion of lignin-derived and carbohydrate-derived renewable building blocks as well as challenging aliphatic alcohols was also achieved. To the best of our knowledge, phenolic primary vanillylamine was obtained as the first example of direct amination of vanillyl alcohol with ammonia via the hydrogen borrowing strategy in good yield. With this particular biobased substrate, the Ni/Al₂O₃–SiO₂/(NH₄)₂CO₃ catalyst system emerged as the best alternative. The described catalytic methodology is atom-economic and environmentally benign, and it uses commercial Ni catalysts and employs easy-to-handle ammonia sources without the need for the addition of gaseous reagents.

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.9b00619.

Detailed spectrometric, chromatographic, and chemical information and ¹H and ¹³C NMR spectral data (PDF)

sc9b00619_si_001.pdf (2.9 MB)

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Author Information

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Corresponding Author
- Katalin Barta - Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands; http://orcid.org/0000-0002-8046-4248; Email: [email protected]
Authors
- Yongzhuang Liu - Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands; Key Laboratory of Bio-Based Material Science and Technology, Ministry of Education, Northeast Forestry University, Harbin 150040, People’s Republic of China
- Anastasiia Afanasenko - Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Saravanakumar Elangovan - Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Zhuohua Sun - Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
Notes
The authors declare no competing financial interest.

Acknowledgments

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K.B. is grateful for financial support from the European Research Council, ERC Starting Grant 2015 (CatASus) 638076. This work is part of the research programme Talent Scheme (Vidi) with project number 723.015.005 (K.B.), which is partly financed by The Netherlands Organization for Scientific Research (NWO). Y.L. is grateful for financial support from the China Scholarship Council (grant number 201706600008).

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Chemical Reviews (Washington, DC, United States) (2016), 116 (22), 14181-14224CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
Amines are key-intermediates in chem. industry due to their nucleophilic characteristic which confers a high reactivity to them. Thus, they are key-monomers for the synthesis of polyamides, polyureas, polyepoxydes···which are all of growing interest in automotive, aerospace, building or health applications. Despite a growing interest for biobased monomers and polymers, and particularly polyamides, it should be noticed that very few natural amines are available. Actually, there is only chitosan and poly(lysine). In this review, we present both fundamental and applied research on the synthesis of biobased primary and secondary amines with current available biobased resources. Their use is described as building block for material chem. Hence, we first recall some background on the synthesis of amines, including the reactivity of amines. Second we focus on the synthesis of biobased amines from all sorts of biomass, from carbohydrate, from terpenes, or from oleochem. sources. Third, because they need optimization and technol. developments, we discuss some examples of their use for the creation of biobased polymers. We conclude on the future of the synthesis of biobased amines and their use in different applications.
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Sun, Z.; Fridrich, B.; De Santi, A.; Elangovan, S.; Barta, K. Bright Side of Lignin Depolymerization: Toward New Platform Chemicals. Chem. Rev. 2018, 118 (2), 614– 678, DOI: 10.1021/acs.chemrev.7b00588
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Bright Side of Lignin Depolymerization: Toward New Platform Chemicals
Sun, Zhuohua; Fridrich, Balint; de Santi, Alessandra; Elangovan, Saravanakumar; Barta, Katalin
Chemical Reviews (Washington, DC, United States) (2018), 118 (2), 614-678CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review. Lignin, a major component of lignocellulose, is the largest source of arom. building blocks on the planet and harbors great potential to serve as starting material for the prodn. of bio-based products. Despite the initial challenges assocd. with the robust and irregular structure of lignin, the valorization of this intriguing arom. biopolymer has come a long way: recently, many creative strategies emerged that deliver defined products via catalytic or biocatalytic depolymn. in good yields. The purpose of this review is to provide insight into these novel approaches and the potential application of such emerging new structures for the synthesis of bio-based polymers or pharmacol. active mols. Existing strategies for functionalization or defunctionalization of lignin based compds. are also summarized. Following the whole value chain from raw lignocellulose through depolymn. to application whenever possible, specific lignin based compds. emerge that could be in the future considered as potential lignin derived platform chems.
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Heuer, L. Benzylamine. Ullmann’s Encyclopedia of Industrial Chemistry; John Wiley & Sons: New York, 2000.
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Mason, A. T. XCV. Preparation of mono-, di-, and tri-benzylamine. J. Chem. Soc., Trans. 1893, 63, 1311, DOI: 10.1039/CT8936301311
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Preparation of mono-, di-, and tri-benzylamine
Mason, Arthur T.
Journal of the Chemical Society, Transactions (1893), 63 (), 1311-1314CODEN: JCHTA3; ISSN:0368-1645.
Cannizzaro observed that when benzylic chloride is heated with an alcoholic solution of ammonia in sealed tubes, it is converted into mono-, di-, and tri-benzylamine. An advantageous method of preparing and isolating the primary and secondary amines has not been based on this observation, although benzylic chloride is a very cheap commercial product. Benzylic chloride is attacked by a cold alcoholic solution of ammonia, and after standing four or five days, the action is complete. Tribenzylamine is the principal product, while with a large excess the tertiary base is formed only in small amounts, the primary and secondary amines as the chief products. The details of the method of preparing mono- and di-benzylamine are presented.
California Research Corp. Preparation of benzylamine, US 2987548, 1961
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Corma, A.; Navas, J.; Sabater, M. J. Advances in One-Pot Synthesis through Borrowing Hydrogen Catalysis. Chem. Rev. 2018, 118 (4), 1410– 1459, DOI: 10.1021/acs.chemrev.7b00340
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Advances in One-Pot Synthesis through Borrowing Hydrogen Catalysis
Corma, Avelino; Navas, Javier; Sabater, Maria J.
Chemical Reviews (Washington, DC, United States) (2018), 118 (4), 1410-1459CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review. The borrowing H (BH) principle, also called H autotransfer, is a powerful approach which combines transfer hydrogenation (avoiding the direct use of mol. H) with one or more intermediate reactions to synthesize more complex mols. without the need for tedious sepn. or isolation processes. The strategy which usually relies on three steps, (i) dehydrogenation, (ii) intermediate reaction, and (iii) hydrogenation is an excellent and well-recognized process from the synthetic, economic, and environmental point of view. In this context, the objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis. Two main subareas of the topic (homogeneous and heterogeneous catalysis) were identified, from which three subheadings based on the source of the electrophile (alkanes, alcs., and amines) were considered. Then the type of bond being formed (C-C and C-heteroatom) was taken into account to end-up with the intermediate reaction working in tandem with the metal-catalyzed hydrogenation/dehydrogenation step. The review was completed with the more recent advances in asym. catalysis using the BH strategy.
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Bähn, S.; Imm, S.; Neubert, L.; Zhang, M.; Neumann, H.; Beller, M. The Catalytic Amination of Alcohols. ChemCatChem 2011, 3 (12), 1853– 1864, DOI: 10.1002/cctc.201100255
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Irrgang, T.; Kempe, R. 3d-Metal Catalyzed N- and C-Alkylation Reactions via Borrowing Hydrogen or Hydrogen Autotransfer. Chem. Rev. 2018, 119 (4), 2524– 2549, DOI: 10.1021/acs.chemrev.8b00306
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Shimizu, K. I. Heterogeneous Catalysis for the Direct Synthesis of Chemicals by Borrowing Hydrogen Methodology. Catal. Sci. Technol. 2015, 5 (3), 1412– 1427, DOI: 10.1039/C4CY01170H
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Heterogeneous catalysis for the direct synthesis of chemicals by borrowing hydrogen methodology
Shimizu, Ken-ichi
Catalysis Science & Technology (2015), 5 (3), 1412-1427CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
A review. The development of heterogeneous catalysts for green chem. synthesis is a growing area in catalysis and green-sustainable chem. This review summarizes recent examples of hydrogen transfer-type reactions using supported transition metal catalysts with special emphasis on the direct synthesis of chems. by borrowing hydrogen methodol. The highlighted reactions are: (1) transfer hydrogenation of carbonyl compds., (2) transfer dehydrogenation of alcs., (3) N-alkylation of amines or NH3 with alcs., (4) alkylation of acidic CH2 or CH3 group with alcs., (5) self- and cross-alkylation of alcs., (6) N- or C3-alkylation of indoles with alcs., (7) synthesis of quinolines from nitroarenes and alcs., (8) synthesis of thioethers from thiols and alcs., and (9) cross-alkylation of amines with different amines. These catalytic reactions have a common mechanistic feature: a domino dehydrogenation-condensation-hydrogenation sequence of alcs. (or amines) and nucleophiles. A key concept in the catalyst design in some of the systems is the multifunctionality of metal-loaded acidic and/or basic metal oxides, in which the acid and/or base sites selectively catalyze the condensation reactions, and the metal site catalyzes the transfer dehydrogenation of alc. (or amines) and transfer hydrogenation of the condensation products as intermediates. In comparison with the recent examples of organometallic catalysis with borrowing hydrogen methodol., the advantages of heterogeneous catalysis are discussed in terms of catalytic efficiency and sustainability.
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Gonzalez-Arellano, C.; Yoshida, K.; Gai, P. L.; Luque, R. Highly Active and Selective Supported Iron Oxide Nanoparticles in Microwave-Assisted N-Alkylations of Amines with Alcohols. Green Chem. 2010, 12 (7), 1281– 1287, DOI: 10.1039/c003410j
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Highly active and selective supported iron oxide nanoparticles in microwave-assisted N-alkylations of amines with alcohols
Gonzalez-Arellano, Camino; Yoshida, Kenta; Luque, Rafael; Gai, Pratibha L.
Green Chemistry (2010), 12 (7), 1281-1287CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
Highly active and stable supported Fe oxide nanoparticles show excellent activities and switchable selectivities to target products in the microwave-assisted N-alkylation of amines with alcs.
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Balu, A. M.; Pineda, A.; Obermayer, D.; Romero, A. A.; Kappe, C. O.; Luque, R. Versatile low-loaded mechanochemically synthesized supported iron oxide nanoparticles for continuous flow alkylations. RSC Adv. 2013, 3 (37), 16292– 16295, DOI: 10.1039/c3ra43160f
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Versatile low-loaded mechanochemically synthesized supported iron oxide nanoparticles for continuous flow alkylation
Balu, Alina M.; Pineda, Antonio; Obermayer, David; Romero, Antonio A.; Kappe, C. Oliver; Luque, Rafael
RSC Advances (2013), 3 (37), 16292-16295CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
A novel and highly versatile mechanochem. synthesized low-loaded (0.25 wt.%) supported iron oxide nanomaterial catalyst has been demonstrated to be highly active and selective for the prodn. of o-(benzyl)(methyl)benzene and p-(benzyl)(methyl)benzene (preferentially) carbon-carbon bond (C-C) alkylated products in a continuous flow alkylation of toluene with benzyl chloride as compared to the etherification product (dibenzyl ether) obsd. in the alkylation of toluene with benzyl alc. The low quantities of highly accessible iron oxide nanoparticles on the external surface of an aluminosilicate support provided versatile acidic sites that were able to promote both the alkylation of toluene with benzyl alc. and benzyl chloride. ICP-MS anal. revealed that the catalyst is highly stable and does not significantly leach under the investigated conditions, providing solid evidence of an iron-catalyzed heterogeneous protocol.
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Gunanathan, C.; Milstein, D. Selective Synthesis of Primary Amines Directly from Alcohols and Ammonia. Angew. Chem., Int. Ed. 2008, 47 (45), 8661– 8664, DOI: 10.1002/anie.200803229
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Selective synthesis of primary amines directly from alcohols and ammonia
Gunanathan, Chidambaram; Milstein, David
Angewandte Chemie, International Edition (2008), 47 (45), 8661-8664CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
Selective and efficient synthesis of primary amines directly from alcs. and ammonia is achieved under mild conditions. The reaction is homogeneously catalyzed by a novel air-stable ruthenium pincer complex and can proceed in toluene or even in the absence of solvent or "on water".
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Imm, S.; Bähn, S.; Zhang, M.; Neubert, L.; Neumann, H.; Klasovsky, F.; Pfeffer, J.; Haas, T.; Beller, M. Improved Ruthenium-Catalyzed Amination of Alcohols with Ammonia: Synthesis of Diamines and Amino Esters. Angew. Chem., Int. Ed. 2011, 50 (33), 7599– 7603, DOI: 10.1002/anie.201103199
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Improved ruthenium-catalyzed amination of alcohols with ammonia: synthesis of diamines and amino esters
Imm, Sebastian; Baehn, Sebastian; Zhang, Min; Neubert, Lorenz; Neumann, Helfried; Klasovsky, Florian; Pfeffer, Jan; Haas, Thomas; Beller, Matthias
Angewandte Chemie, International Edition (2011), 50 (33), 7599-7603, S7599/1-S7599/11CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A homogeneous selective catalytic amination of primary and secondary diols with ammonia is described. Catalyzed by [Ru(CO)ClH(PPh3)3]/Xantphos, the corresponding diamines were obtained in good yields using this method.
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Fujita, K.; Furukawa, S.; Morishima, N.; Shimizu, M.; Yamaguchi, R. N-Alkylation of Aqueous Ammonia with Alcohols Leading to Primary Amines Catalyzed by Water-Soluble N-Heterocyclic Carbene Complexes of Iridium. ChemCatChem 2018, 10 (9), 1993– 1997, DOI: 10.1002/cctc.201702037
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N-Alkylation of Aqueous Ammonia with Alcohols Leading to Primary Amines Catalyzed by Water-Soluble N-Heterocyclic Carbene Complexes of Iridium
Fujita, Ken-ichi; Furukawa, Shohichi; Morishima, Namino; Shimizu, Mineyuki; Yamaguchi, Ryohei
ChemCatChem (2018), 10 (9), 1993-1997CODEN: CHEMK3; ISSN:1867-3880. (Wiley-VCH Verlag GmbH & Co. KGaA)
A new catalytic system for the N-monoalkylation of aq. ammonia with a variety of alcs. was developed. Water-sol. dicationic complexes of iridium bearing N-heterocyclic carbene and diammine ligands exhibited high catalytic activity for this type of reaction on the basis of hydrogen-transfer processes without generating harmful or wasteful byproducts. Various primary amines were efficiently synthesized by using safe, inexpensive, and easily handled aq. ammonia as a nitrogen source. For example, the reaction of 1-(4-methylphenyl)ethanol with aq. ammonia in the presence of a water-sol. N-heterocyclic carbene complex of iridium at 150° for 40 h gave 1-(4-methylphenyl)ethylamine in 83% yield.
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Shimizu, K. I.; Kon, K.; Onodera, W.; Yamazaki, H.; Kondo, J. N. Heterogeneous Ni Catalyst for Direct Synthesis of Primary Amines from Alcohols and Ammonia. ACS Catal. 2013, 3 (1), 112– 117, DOI: 10.1021/cs3007473
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Heterogeneous Ni Catalyst for Direct Synthesis of Primary Amines from Alcohols and Ammonia
Shimizu, Ken-ichi; Kon, Kenichi; Onodera, Wataru; Yamazaki, Hiroshi; Kondo, Junko N.
ACS Catalysis (2013), 3 (1), 112-117CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
This paper reports the synthesis of primary amines from alcs. and NH3 by an Al2O3-supported nickel nanoparticle catalyst as the first example of heterogeneous and noble metal-free catalytic system for this reaction without addnl. hydrogen sources under relatively mild conditions. Various aliph. alcs. are tolerated, and turnover nos. were higher than those of ruthenium-based homogeneous catalysts. The catalyst was recoverable and was reused. The effects of the nickel oxidn. states and the acid-base nature of support oxides on the catalytic activity were studied. It is clarified that the surface metallic nickel sites are the catalytically active species, and the co-presence of acidic and basic sites on the support surface is also indispensable for this catalytic system.
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Shimizu, K. I.; Kanno, S.; Kon, K.; Hakim Siddiki, S. M. A.; Tanaka, H.; Sakata, Y. N-Alkylation of Ammonia and Amines with Alcohols Catalyzed by Ni-Loaded CaSiO₃. Catal. Today 2014, 232, 134– 138, DOI: 10.1016/j.cattod.2013.09.002
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N-alkylation of ammonia and amines with alcohols catalyzed by Ni-loaded CaSiO3
Shimizu, Ken-ichi; Kanno, Shota; Kon, Kenichi; Hakim Siddiki, S. M. A.; Tanaka, Hideyuki; Sakata, Yoshihisa
Catalysis Today (2014), 232 (), 134-138CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
Nickel nanoparticles loaded onto calcium silicate (Ni/CaSiO3) were prepd. by ion-exchange method followed by in situ H2-redn. of the calcined precursor. Ni/CaSiO3 is effective for the catalytic direct synthesis of primary amines from alcs. and NH3 under relatively mild conditions. Various aliph. alcs. are tolerated, and the turnover no. (TON) was higher than those of Ru-based homogeneous catalysts. The catalyst was recoverable and was reused. Effects of the surface oxidn. states and particle size of Ni on the catalytic activity were studied by IR study of the states of adsorbed CO and TEM. The surface Ni0 sites on small (3 nm) sized Ni nanoparticles are the catalytically active species. Ni/CaSiO3 was also effective for the alkylation of anilines and aliph. amines with various alcs. (benzyl and aliph. alcs.) under additive free conditions; primary amines were converted into secondary amines and secondary amines into tertiary amines.
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Cui, X.; Dai, X.; Deng, Y.; Shi, F. Development of a General Non-Noble Metal Catalyst for the Benign Amination of Alcohols with Amines and Ammonia. Chem. - Eur. J. 2013, 19 (11), 3665– 3675, DOI: 10.1002/chem.201203417
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Development of a general non-noble metal catalyst for the benign amination of alcohols with amines and ammonia
Cui, Xinjiang; Dai, Xingchao; Deng, Youquan; Shi, Feng
Chemistry - A European Journal (2013), 19 (11), 3665-3675CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
The N-alkylation of amines or ammonia with alcs. is a valuable route for the synthesis of N-alkyl amines. However, as a potentially clean and economic choice for N-alkyl amine synthesis, non-noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeOx catalyst was designed and prepd. for the N-alkylation of ammonia or amines with alc. or primary amines. N-alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of org. ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N-heterocyclic compds., and secondary amines could be N-alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one-pot reaction of ammonia and alcs. In addn. to excellent catalytic performance, the catalyst itself possesses outstanding superiority, i.e., it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixt. and it could be recovered and reused for several runs without obvious deactivation. Nitric acid, copper(2+) salt (2:1).
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Leung, A. Y. K.; Hellgardt, K.; Hii, K. K. M. Catalysis in Flow: Nickel-Catalyzed Synthesis of Primary Amines from Alcohols and NH₃. ACS Sustainable Chem. Eng. 2018, 6 (4), 5479– 5484, DOI: 10.1021/acssuschemeng.8b00338
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Catalysis in Flow: Nickel-Catalyzed Synthesis of Primary Amines from Alcohols and NH3
Leung, Andrew Yuk Keung; Hellgardt, Klaus; Hii, King Kuok "Mimi"
ACS Sustainable Chemistry & Engineering (2018), 6 (4), 5479-5484CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
A highly selective synthesis of primary amines from alcs. and NH3 was achieved on using a com. available Ni catalyst, without adding H2. Using a continuous flow reaction platform, the amination of aliph. alcs. can be achieved in good yields and selectivities, as the accumulation of water byproduct can be removed. Competitive formation of the nitrile side-product was suppressed when the catalyst was prereduced. Modes of catalyst deactivation were also briefly examd.
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Dimmel, D. R.; Shepard, D.; Brown, T. A. The Influence of Anthrahydroquinone and Other Additives on the Condensation Reactions of Vanillyl Alcohol. J. Wood Chem. Technol. 1981, 1 (2), 123– 146, DOI: 10.1080/02773818108085109
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The influence of anthrahydroquinone and other additives on the condensation reactions of vanillyl alcohol
Dimmel, Donald R.; Shepard, Donaline; Brown, Thomas A.
Journal of Wood Chemistry and Technology (1981), 1 (2), 123-46CODEN: JWCTDJ; ISSN:0277-3813.
Alkali cooking of vanillyl alc. [498-00-0] as a model for lignin in the presence of anthrahydroquinone [4981-66-2], generated from anthraquinone and glucose or Na2S2O4, 3,5-dinitrobenzoic acid [99-34-3], and Na2S resulted in the formation of dimers and trimers, and these additives greatly depressed the levels of condensation products. The detection of dimers and trimers suggested some radical intermediates are present under these reaction conditions, and the degree of condensation and ratio of products were temp. dependent. The effect of selected additives on the condensation reaction of dioxane lignin [8068-03-9] was also detd.
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Reashad Bin Kabir, E.; Nasrin Ferdous, E. Kevlar-The Super Tough Fiber. Int. J. Text. Sci. 2012, 1 (6), 78– 83, DOI: 10.5923/j.textile.20120106.04
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Borkowski, T.; Dobosz, J.; Tylus, W.; Trzeciak, A. M. Palladium Supported on Al₂O₃-CeO₂ Modified with Ionic Liquids as a Highly Active Catalyst of the Suzuki-Miyaura Cross-Coupling. J. Catal. 2014, 319, 87– 94, DOI: 10.1016/j.jcat.2014.08.007
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Palladium supported on Al2O3-CeO2 modified with ionic liquids as a highly active catalyst of the Suzuki-Miyaura cross-coupling
Borkowski, Tomasz; Dobosz, Justyna; Tylus, Wlodzimierz; Trzeciak, Anna M.
Journal of Catalysis (2014), 319 (), 87-94CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
Palladium catalysts immobilized on Al2O3-CeO2 and modified with ionic liqs. (ILs), formed Suzuki-Miyaura products with yields of up to 97%. A catalyst contg. [bmim]BF4 showed unchanged activity in three consecutive runs. During the Suzuki-Miyaura reaction, Pd(0) nanoparticles were formed with a diam. of 6-10 nm depending on the kind of IL used. The distribution of palladium inside the Al2O3-CeO2 support was not uniform, with the max. in the central part of the wire. The migration of palladium in the support was obsd. during the reaction.
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Eremin, D. B.; Ananikov, V. P. Understanding Active Species in Catalytic Transformations: From Molecular Catalysis to Nanoparticles, Leaching, “Cocktails” of Catalysts and Dynamic Systems. Coord. Chem. Rev. 2017, 346, 2– 19, DOI: 10.1016/j.ccr.2016.12.021
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Understanding active species in catalytic transformations: From molecular catalysis to nanoparticles, leaching, "Cocktails" of catalysts and dynamic systems
Eremin, Dmitry B.; Ananikov, Valentine P.
Coordination Chemistry Reviews (2017), 346 (), 2-19CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
In the present review, we consider the transformations of mol. catalysts, leaching, aggregation and various interconversions of metal complexes, clusters and nanoparticles that occur during catalytic processes. The role of catalyst evolution and the mechanistic picture of "Cocktail"-type systems are considered from the perspective of the development of a new generation of efficient, selective and re-usable catalysts for synthetic applications. Rational catalyst development and the improvement of catalyst performance cannot be achieved without an understanding of the dynamic nature of catalytic systems.
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Hahn, G.; Kunnas, P.; de Jonge, N.; Kempe, R. General synthesis of primary amines via reductive amination employing a reusable nickel catalyst. Nat. Catal. 2019, 2, 71– 77, DOI: 10.1038/s41929-018-0202-6
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General synthesis of primary amines via reductive amination employing a reusable nickel catalyst
Hahn, G.; Kunnas, P.; de Jonge, N.; Kempe, R.
Nature Catalysis (2019), 2 (1), 71-77CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
A nanostructured nickel catalyst was reported for the general and selective synthesis of primary amines via reductive amination, employing ammonia dissolved in water. The catalyst, which operated at low temp. and pressure, was highly active, reusable and easy to handle. The synthesis from a specific nickel complex and γ-Al2O3 was straightforward, with the ligand-metal combination of this complex being crucial. Aldehydes (including purely aliph. ones), aryl-alkyl, dialkyl and diaryl ketones could all be converted smoothly into primary amines. In addn., the amination of pharmaceuticals, bioactive compds. and natural products was demonstrated. Many functional groups-including hydrogenation-sensitive examples-were tolerated.
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Wang, Y.; Shao, Z.; Zhang, K.; Liu, Q. Manganese-Catalyzed Dual-Deoxygenative Coupling of Primary Alcohols with 2-Arylethanols. Angew. Chem., Int. Ed. 2018, 130 (46), 15363– 15367, DOI: 10.1002/anie.201809333
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Fache, M.; Boutevin, B.; Caillol, S. Vanillin Production from Lignin and Its Use as a Renewable Chemical. ACS Sustainable Chem. Eng. 2016, 4 (1), 35– 46, DOI: 10.1021/acssuschemeng.5b01344
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Vanillin Production from Lignin and Its Use as a Renewable Chemical
Fache, Maxence; Boutevin, Bernard; Caillol, Sylvain
ACS Sustainable Chemistry & Engineering (2016), 4 (1), 35-46CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
A review. The use of vanillin as a building block for the chem. industry is discussed in this article. Vanillin is currently one of the only mol. phenolic compds. manufd. on an industrial scale from biomass. It has thus the potential to become a key-intermediate for the synthesis of bio-based polymers, for which arom. monomers are needed to reach good thermo-mech. properties. After a first part dedicated to the current sousing of vanillin, this article focuses on the alk. oxidn. lignin-to-vanillin process, reporting advantages and limits, discusses the various post-depolymn. methods for product isolation and finally examines the outlook for the wider use of vanillin as a key building block for the chem. industry.
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Tarabanko, V. E.; Tarabanko, N. Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects. Int. J. Mol. Sci. 2017, 18 (11), 2421, DOI: 10.3390/ijms18112421
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Catalytic oxidation of lignins into the aromatic aldehydes: general process trends and development prospects
Tarabanko, Valery E.; Tarabanko, Nikolay
International Journal of Molecular Sciences (2017), 18 (11), 2421/1-2421/29CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)
A review. This review discusses principal patterns that govern the processes of lignins' catalytic oxidn. into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temp., mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidn. of various lignins are only insignificantly (10-15%) inferior to oxidn. by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process-over 10 mol per mol of obtained vanillin-is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidn. into the arom. aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidn. of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the arom. aldehydes and cellulose are analyzed.
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Vangeel, T.; Schutyser, W.; Renders, T.; Sels, B. F. Perspective on Lignin Oxidation: Advances, Challenges, and Future Directions. Top. Curr. Chem. 2018, 376 (4), 30, DOI: 10.1007/s41061-018-0207-2
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Perspective on Lignin Oxidation: Advances, Challenges, and Future Directions
Vangeel Thijs; Schutyser Wouter; Renders Tom; Sels Bert F
Topics in current chemistry (Cham) (2018), 376 (4), 30 ISSN:2365-0869.
Lignin valorization has gained increasing attention over the past decade. Being the world's largest source of renewable aromatics, its valorization could pave the way towards more profitable and more sustainable lignocellulose biorefineries. Many lignin valorization strategies focus on the disassembly of lignin into aromatic monomers, which can serve as platform molecules for the chemical industry. Within this framework, the oxidative conversion of lignin is of great interest because it enables the formation of highly functionalized, valuable compounds. This work provides a brief overview and critical discussion of lignin oxidation research. In the first part, oxidative conversion of lignin models and isolated lignin streams is reviewed. The second part highlights a number of challenges with respect to the substrate, catalyst, and operating conditions, and proposes some future directions regarding the oxidative conversion of lignin.
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Aiello, F.; Badolato, M.; Pessina, F.; Sticozzi, C.; Maestrini, V.; Aldinucci, C.; Luongo, L.; Guida, F.; Ligresti, A.; Artese, A. Design and Synthesis of New Transient Receptor Potential Vanilloid Type-1 (TRPV1) Channel Modulators: Identification, Molecular Modeling Analysis, and Pharmacological Characterization of the N -(4-Hydroxy-3-Methoxybenzyl)-4-(Thiophen-2-Yl)butanamid. ACS Chem. Neurosci. 2016, 7 (6), 737– 748, DOI: 10.1021/acschemneuro.5b00333
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Design and Synthesis of New Transient Receptor Potential Vanilloid Type-1 (TRPV1) Channel Modulators: Identification, Molecular Modeling Analysis, and Pharmacological Characterization of the N-(4-Hydroxy-3-methoxybenzyl)-4-(thiophen-2-yl)butanamide, a Small Molecule Endowed with Agonist TRPV1 Activity and Protective Effects against Oxidative Stress
Aiello, Francesca; Badolato, Mariateresa; Pessina, Federica; Sticozzi, Claudia; Maestrini, Vanessa; Aldinucci, Carlo; Luongo, Livio; Guida, Francesca; Ligresti, Alessia; Artese, Anna; Allara, Marco; Costa, Giosue; Frosini, Maria; Schiano Moriello, Aniello; De Petrocellis, Luciano; Valacchi, Giuseppe; Alcaro, Stefano; Maione, Sabatino; Di Marzo, Vincenzo; Corelli, Federico; Brizzi, Antonella
ACS Chemical Neuroscience (2016), 7 (6), 737-748CODEN: ACNCDM; ISSN:1948-7193. (American Chemical Society)
4-(Thiophen-2-yl)butanoic acid was identified as a cyclic substitute of the unsatd. alkyl chain of the natural ligand, capsaicin. Accordingly, a new class of amides was synthesized in good yield and high purity and their mol. recognition against the target was investigated by means of docking expts. followed by mol. dynamics simulations, in order to rationalize their geometrical and thermodn. profiles. The pharmacol. properties of these new compds. were expressed as activation (EC50) and desensitization (IC50) potencies. Several compds. were found to activate TRPV1 channels, and in particular, derivs. I and II behaved as TRPV1 agonists endowed with good efficacy as compared to capsaicin. The most promising compd. I was also evaluated for its protective role against oxidative stress on keratinocytes and differentiated human neuroblastoma cell lines expressing the TRPV1 receptor as well as for its cytotoxicity and analgesic activity in vivo.
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Yu, Y.-F.; Huang, Y.-D.; Zhang, C.; Wu, X.-N.; Zhou, Q.; Wu, D.; Wu, Y.; Luo, H.-B. Discovery of Novel Pyrazolopyrimidinone Derivatives as Phosphodiesterase 9A Inhibitors Capable of Inhibiting Butyrylcholinesterase for Treatment of Alzheimer’s Disease. ACS Chem. Neurosci. 2017, 8 (11), 2522– 2534, DOI: 10.1021/acschemneuro.7b00268
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Discovery of Novel Pyrazolopyrimidinone Derivatives as Phosphodiesterase 9A Inhibitors Capable of Inhibiting Butyrylcholinesterase for Treatment of Alzheimer's Disease
Yu, Yan-Fa; Huang, Ya-Dan; Zhang, Chen; Wu, Xu-Nian; Zhou, Qian; Wu, Deyan; Wu, Yinuo; Luo, Hai-Bin
ACS Chemical Neuroscience (2017), 8 (11), 2522-2534CODEN: ACNCDM; ISSN:1948-7193. (American Chemical Society)
Discovery of multitarget directed ligands (MTDLs) targeting at different factors simultaneously to control the complicated pathogenesis of Alzheimer's disease (AD), has become an important research area in recent years. Both PDE9A and BuChE inhibitors could participate in different processes of AD to attenuate neuronal injuries and improve cognitive impairments. However, research on the MTDLs combining the inhibition of PDE9A and BuChE simultaneously has not been reported yet. In this study, a series of novel pyrazolopyrimidinone-rivastigmine hybrids were designed, synthesized, and evaluated in vitro. Most compds. exhibited remarkable inhibitory activities against both PDE9A and BuChE. Compds. I and II showed the best IC50 values against PDE9A (I: 14 nM, II:17 nM, resp.) together with the considerable inhibition against BuChE (IC50, I: 3.3 μM, II: 0.97 μM). Their inhibitory potencies against BuChE were even higher than the anti-AD drug rivastigmine. Worthy to mention is that both showed moderate selectivity for BuChE over AChE. Mol. docking studies revealed their binding patters and explained the influence of configuration and substitutions on the inhibition of PDE9A and BuChE. Furthermore, compds. I and II exhibited negligible toxicity, which made them suitable for the further study of AD in vivo.
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Fache, M.; Montérémal, C.; Boutevin, B.; Caillol, S. Amine Hardeners and Epoxy Cross-Linker from Aromatic Renewable Resources. Eur. Polym. J. 2015, 73, 344– 362, DOI: 10.1016/j.eurpolymj.2015.10.032
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Amine hardeners and epoxy cross-linker from aromatic renewable resources
Fache, Maxence; Monteremal, Camille; Boutevin, Bernard; Caillol, Sylvain
European Polymer Journal (2015), 73 (), 344-362CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
Bio-based epoxy thermosets are currently extensively studied. To be industrially relevant, bio-based epoxy formulations must be tailored so that the properties of the resulting thermosets can be conveniently controlled. This can be achieved by choosing the right hardener. Amine hardeners were thus synthesized from potentially bio-sourced vanillin and furfural. These compds. are also arom., an important structural feature to reach good thermo-mech. properties. A tri-functional, vanillin-derived epoxy cross-linker was also synthesized. Multi-functional epoxy monomers can increase the crosslinking d. of the network, which is another convenient way of controlling the final properties. Epoxy thermosets were prepd. from bio-based epoxy monomers and hardeners, and from ref. compds. commonly used in industry. These polymers were characterized and structure-property relationships are discussed.
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Yan, T.; Feringa, B. L.; Barta, K. Iron Catalysed Direct Alkylation of Amines with Alcohols. Nat. Commun. 2014, 5, 5602, DOI: 10.1038/ncomms6602
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Iron catalyzed direct alkylation of amines with alcohols
Yan, Tao; Feringa, Ben L.; Barta, Katalin
Nature Communications (2014), 5 (), 5602CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
The selective conversion of carbon-oxygen bonds into carbon-nitrogen bonds to form amines was one of the most important chem. transformations for the prodn. of bulk and fine chems. and pharma intermediates. An atom-economic way of carrying out such C-N bond formations was the direct N-alkylation of simple amines with alcs. by borrowing hydrogen strategy. Transition metal complexes based on precious metals have emerged as suitable catalysts for this transformation; however, the crucial change towards the use of abundant, inexpensive and environmentally friendly metals, in particular iron, has not yet been accomplished. The homogeneous, iron-catalyzed, direct alkylation of amines with alcs. was described. The scope of this new methodol. includes the monoalkylation of anilines and benzyl amines with a wide range of alcs., and the use of diols in the formation of five, six- and seven- membered nitrogen heterocycles, which are privileged structures in numerous pharmaceuticals.
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Afanasenko, A.; Elangovan, S.; Stuart, M. C. A.; Bonura, G.; Frusteri, F.; Barta, K. Efficient Nickel-Catalysed: N-Alkylation of Amines with Alcohols. Catal. Sci. Technol. 2018, 8 (21), 5498– 5505, DOI: 10.1039/C8CY01200H
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Efficient nickel-catalysed N-alkylation of amines with alcohols
Afanasenko, Anastasiia; Elangovan, Saravanakumar; Stuart, Marc C. A.; Bonura, Giuseppe; Frusteri, Francesco; Barta, Katalin
Catalysis Science & Technology (2018), 8 (21), 5498-5505CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
In the presence of nickel nanoparticles generated in situ from Ni(cod)2 and KOH, arylamines underwent chemoselective alkylation with alkyl and benzylic alcs. and diols to yield N-monoalkylated arylamines. The morphol. of the nickel nanoparticles generated was characterized by TEM; reactions of arylamines and alkylamines yielded nanoparticles with differing morphologies, consistent with their differences in reactivity. The nanoparticles were used four times in alkylation reactions, but gave products in decreasing yields.
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Sun, Z.; Bottari, G.; Afanasenko, A.; Stuart, M. C. A.; Deuss, P. J.; Fridrich, B.; Barta, K. Complete Lignocellulose Conversion with Integrated Catalyst Recycling Yielding Valuable Aromatics and Fuels. Nat. Catal. 2018, 1 (1), 82– 92, DOI: 10.1038/s41929-017-0007-z
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Complete lignocellulose conversion with integrated catalyst recycling yielding valuable aromatics and fuels
Sun, Zhuohua; Bottari, Giovanni; Afanasenko, Anastasiia; Stuart, Marc C. A.; Deuss, Peter J.; Fridrich, Balint; Barta, Katalin
Nature Catalysis (2018), 1 (1), 82-92CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
Lignocellulose, the main component of agricultural and forestry waste, harbours tremendous potential as a renewable starting material for future biorefinery practices. However, this potential remains largely unexploited due to the lack of strategies that derive substantial value from its main constituents. Here, we present a catalytic strategy that is able to transform lignocellulose to a range of attractive products. At the center of our approach is the flexible use of a non-precious metal catalyst in two distinct stages of a lignocellulose conversion process that enables integrated catalyst recycling through full conversion of all process residues. From the lignin, pharmaceutical and polymer building blocks are obtained. Notably, among these pathways are systematic chemo-catalytic methodologies to yield amines from lignin. The (hemi)cellulose-derived aliph. alcs. are transformed to alkanes, achieving excellent total carbon utilization. This work will inspire the development of fully sustainable and economically viable biorefineries.
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Hemmingson, Jacqueline A.; Leary, Gordon
Australian Journal of Chemistry (1980), 33 (4), 917-25CODEN: AJCHAS; ISSN:0004-9425.
Self-condensation of vanillyl alc. [498-00-0] and veratryl alc. [93-03-8] as models for lignin in H2O or aq. EtOH resulted in formation of benzyl ether and diphenylmethane structures. The results of the study suggested that condensation reactions between p-hydroxybenzyl alc. structures may also occur in the lignin of long-lived species of plants as the plant ages.
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Abbott, J. R.; Patel, P. A.; Howes, J. E.; Akan, D. T.; Kennedy, J. P.; Burns, M. C.; Browning, C. F.; Sun, Q.; Rossanese, O. W.; Phan, J. Discovery of Quinazolines That Activate SOS1-Mediated Nucleotide Exchange on RAS. ACS Med. Chem. Lett. 2018, 9 (9), 941– 946, DOI: 10.1021/acsmedchemlett.8b00296
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Abbott, Jason R.; Patel, Pratiq A.; Howes, Jennifer E.; Akan, Denis T.; Kennedy, J. Phillip; Burns, Michael C.; Browning, Carrie F.; Sun, Qi; Rossanese, Olivia W.; Phan, Jason; Waterson, Alex G.; Fesik, Stephen W.
ACS Medicinal Chemistry Letters (2018), 9 (9), 941-946CODEN: AMCLCT; ISSN:1948-5875. (American Chemical Society)
Proteins in the RAS family are important regulators of cellular signaling and, when mutated, can drive cancer pathogenesis. Despite considerable effort over the last 30 years, RAS proteins have proven to be recalcitrant therapeutic targets. One approach for modulating RAS signaling is to target proteins that interact with RAS, such as the guanine nucleotide exchange factor (GEF) son of sevenless homolog 1 (SOS1). Here, we report hit-to-lead studies on quinazoline-contg. compds. that bind to SOS1 and activate nucleotide exchange on RAS. Using structure-based design, we refined the substituents attached to the quinazoline nucleus and built in addnl. interactions not present in the initial HTS hit. Optimized compds. activate nucleotide exchange at single-digit micromolar concns. in vitro. In HeLa cells, these quinazolines increase the levels of RAS-GTP and cause signaling changes in the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway.
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Akram Ashouri, Saadi Samadi, Masoud Ahmadian, Behzad Nasiri. Copper-catalyzed synthesis of diarylamines using p-toluene sulfonamides and benzhydrol derivatives under homogeneous borrowing hydrogen conditions. Comptes Rendus. Chimie 2020, 23 (1) , 47-55. https://doi.org/10.5802/crchim.5
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ACS Sustainable Chemistry & Engineering

Cite this: ACS Sustainable Chem. Eng. 2019, 7, 13, 11267–11274

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https://doi.org/10.1021/acssuschemeng.9b00619

Published May 31, 2019

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Abstract
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Figure 1
Figure 1. (a) Possible biobased amine building blocks from lignocellulose. (b) General mechanism of the “hydrogen borrowing” strategy. (c) Representative examples of bioactive molecules comprising benzylamine moieties or furfurylamine.
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Scheme 1
Scheme 1. Possible Reaction Pathways during Direct Amination of Benzyl Alcohol with Ammonia Using Raney Ni As Hydrogen Transfer Catalyst
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Figure 2
Figure 2. Influence of various reaction parameters on the selectivity of primary benzylamines. Varying amounts of (a) catalyst (50–400 mg), (b) ammonia equivalents (1.3–7.8 mmol), (c) reaction temperatures (160–180 °C, 18 h), and (d) reaction time (180 °C, 2–24 h). General reaction conditions: general procedure 1, benzyl alcohol (1 mmol), aq. NH₃ (25 wt %), Raney Ni 2800, and dodecane (internal standard, 20 μL).
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Figure 3
Figure 3. Comparison study between Raney Ni (gray region) and Ni/Al₂O₃–SiO₂(white region) catalyzed vanillyl alcohol amination with various ammonia sources. General reaction conditions: general procedure 2, 200 mg of Ni catalyst, 0.5 mmol of substrate, 2 equiv of NH₃ in ammonia salts, 140 °C, 18 h; conversion and selectivity values were calculated by GC-FID. For aq. NH₃: 0.4 mL aq. NH₃, 3 mL t-amyl alcohol as solvent. For NH₃ in organic solvents: directly use 3 mL of ammonia in dioxane (0.5 M) or THF (0.4 M) as both solvent and ammonia source.
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Figure 4
Figure 4. Possible dimerization byproducts detected from amination reaction of vanillyl alcohol.
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References
This article references 37 other publications.
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  A review. The borrowing H (BH) principle, also called H autotransfer, is a powerful approach which combines transfer hydrogenation (avoiding the direct use of mol. H) with one or more intermediate reactions to synthesize more complex mols. without the need for tedious sepn. or isolation processes. The strategy which usually relies on three steps, (i) dehydrogenation, (ii) intermediate reaction, and (iii) hydrogenation is an excellent and well-recognized process from the synthetic, economic, and environmental point of view. In this context, the objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis. Two main subareas of the topic (homogeneous and heterogeneous catalysis) were identified, from which three subheadings based on the source of the electrophile (alkanes, alcs., and amines) were considered. Then the type of bond being formed (C-C and C-heteroatom) was taken into account to end-up with the intermediate reaction working in tandem with the metal-catalyzed hydrogenation/dehydrogenation step. The review was completed with the more recent advances in asym. catalysis using the BH strategy.
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  Heterogeneous catalysis for the direct synthesis of chemicals by borrowing hydrogen methodology
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  Heterogeneous Ni Catalyst for Direct Synthesis of Primary Amines from Alcohols and Ammonia
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  This paper reports the synthesis of primary amines from alcs. and NH3 by an Al2O3-supported nickel nanoparticle catalyst as the first example of heterogeneous and noble metal-free catalytic system for this reaction without addnl. hydrogen sources under relatively mild conditions. Various aliph. alcs. are tolerated, and turnover nos. were higher than those of ruthenium-based homogeneous catalysts. The catalyst was recoverable and was reused. The effects of the nickel oxidn. states and the acid-base nature of support oxides on the catalytic activity were studied. It is clarified that the surface metallic nickel sites are the catalytically active species, and the co-presence of acidic and basic sites on the support surface is also indispensable for this catalytic system.
17. 17
  Shimizu, K. I.; Kanno, S.; Kon, K.; Hakim Siddiki, S. M. A.; Tanaka, H.; Sakata, Y. N-Alkylation of Ammonia and Amines with Alcohols Catalyzed by Ni-Loaded CaSiO₃. Catal. Today 2014, 232, 134– 138, DOI: 10.1016/j.cattod.2013.09.002
  17
  N-alkylation of ammonia and amines with alcohols catalyzed by Ni-loaded CaSiO3
  Shimizu, Ken-ichi; Kanno, Shota; Kon, Kenichi; Hakim Siddiki, S. M. A.; Tanaka, Hideyuki; Sakata, Yoshihisa
  Catalysis Today (2014), 232 (), 134-138CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
  Nickel nanoparticles loaded onto calcium silicate (Ni/CaSiO3) were prepd. by ion-exchange method followed by in situ H2-redn. of the calcined precursor. Ni/CaSiO3 is effective for the catalytic direct synthesis of primary amines from alcs. and NH3 under relatively mild conditions. Various aliph. alcs. are tolerated, and the turnover no. (TON) was higher than those of Ru-based homogeneous catalysts. The catalyst was recoverable and was reused. Effects of the surface oxidn. states and particle size of Ni on the catalytic activity were studied by IR study of the states of adsorbed CO and TEM. The surface Ni0 sites on small (3 nm) sized Ni nanoparticles are the catalytically active species. Ni/CaSiO3 was also effective for the alkylation of anilines and aliph. amines with various alcs. (benzyl and aliph. alcs.) under additive free conditions; primary amines were converted into secondary amines and secondary amines into tertiary amines.
18. 18
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  18
  Development of a general non-noble metal catalyst for the benign amination of alcohols with amines and ammonia
  Cui, Xinjiang; Dai, Xingchao; Deng, Youquan; Shi, Feng
  Chemistry - A European Journal (2013), 19 (11), 3665-3675CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
  The N-alkylation of amines or ammonia with alcs. is a valuable route for the synthesis of N-alkyl amines. However, as a potentially clean and economic choice for N-alkyl amine synthesis, non-noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeOx catalyst was designed and prepd. for the N-alkylation of ammonia or amines with alc. or primary amines. N-alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of org. ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N-heterocyclic compds., and secondary amines could be N-alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one-pot reaction of ammonia and alcs. In addn. to excellent catalytic performance, the catalyst itself possesses outstanding superiority, i.e., it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixt. and it could be recovered and reused for several runs without obvious deactivation. Nitric acid, copper(2+) salt (2:1).
19. 19
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  19
  Catalysis in Flow: Nickel-Catalyzed Synthesis of Primary Amines from Alcohols and NH3
  Leung, Andrew Yuk Keung; Hellgardt, Klaus; Hii, King Kuok "Mimi"
  ACS Sustainable Chemistry & Engineering (2018), 6 (4), 5479-5484CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
  A highly selective synthesis of primary amines from alcs. and NH3 was achieved on using a com. available Ni catalyst, without adding H2. Using a continuous flow reaction platform, the amination of aliph. alcs. can be achieved in good yields and selectivities, as the accumulation of water byproduct can be removed. Competitive formation of the nitrile side-product was suppressed when the catalyst was prereduced. Modes of catalyst deactivation were also briefly examd.
20. 20
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  22
  Palladium supported on Al2O3-CeO2 modified with ionic liquids as a highly active catalyst of the Suzuki-Miyaura cross-coupling
  Borkowski, Tomasz; Dobosz, Justyna; Tylus, Wlodzimierz; Trzeciak, Anna M.
  Journal of Catalysis (2014), 319 (), 87-94CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
  Palladium catalysts immobilized on Al2O3-CeO2 and modified with ionic liqs. (ILs), formed Suzuki-Miyaura products with yields of up to 97%. A catalyst contg. [bmim]BF4 showed unchanged activity in three consecutive runs. During the Suzuki-Miyaura reaction, Pd(0) nanoparticles were formed with a diam. of 6-10 nm depending on the kind of IL used. The distribution of palladium inside the Al2O3-CeO2 support was not uniform, with the max. in the central part of the wire. The migration of palladium in the support was obsd. during the reaction.
23. 23
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  23
  Understanding active species in catalytic transformations: From molecular catalysis to nanoparticles, leaching, "Cocktails" of catalysts and dynamic systems
  Eremin, Dmitry B.; Ananikov, Valentine P.
  Coordination Chemistry Reviews (2017), 346 (), 2-19CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
  In the present review, we consider the transformations of mol. catalysts, leaching, aggregation and various interconversions of metal complexes, clusters and nanoparticles that occur during catalytic processes. The role of catalyst evolution and the mechanistic picture of "Cocktail"-type systems are considered from the perspective of the development of a new generation of efficient, selective and re-usable catalysts for synthetic applications. Rational catalyst development and the improvement of catalyst performance cannot be achieved without an understanding of the dynamic nature of catalytic systems.
24. 24
  Hahn, G.; Kunnas, P.; de Jonge, N.; Kempe, R. General synthesis of primary amines via reductive amination employing a reusable nickel catalyst. Nat. Catal. 2019, 2, 71– 77, DOI: 10.1038/s41929-018-0202-6
  24
  General synthesis of primary amines via reductive amination employing a reusable nickel catalyst
  Hahn, G.; Kunnas, P.; de Jonge, N.; Kempe, R.
  Nature Catalysis (2019), 2 (1), 71-77CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
  A nanostructured nickel catalyst was reported for the general and selective synthesis of primary amines via reductive amination, employing ammonia dissolved in water. The catalyst, which operated at low temp. and pressure, was highly active, reusable and easy to handle. The synthesis from a specific nickel complex and γ-Al2O3 was straightforward, with the ligand-metal combination of this complex being crucial. Aldehydes (including purely aliph. ones), aryl-alkyl, dialkyl and diaryl ketones could all be converted smoothly into primary amines. In addn., the amination of pharmaceuticals, bioactive compds. and natural products was demonstrated. Many functional groups-including hydrogenation-sensitive examples-were tolerated.
25. 25
  Wang, Y.; Shao, Z.; Zhang, K.; Liu, Q. Manganese-Catalyzed Dual-Deoxygenative Coupling of Primary Alcohols with 2-Arylethanols. Angew. Chem., Int. Ed. 2018, 130 (46), 15363– 15367, DOI: 10.1002/anie.201809333
  There is no corresponding record for this reference.
26. 26
  Fache, M.; Boutevin, B.; Caillol, S. Vanillin Production from Lignin and Its Use as a Renewable Chemical. ACS Sustainable Chem. Eng. 2016, 4 (1), 35– 46, DOI: 10.1021/acssuschemeng.5b01344
  26
  Vanillin Production from Lignin and Its Use as a Renewable Chemical
  Fache, Maxence; Boutevin, Bernard; Caillol, Sylvain
  ACS Sustainable Chemistry & Engineering (2016), 4 (1), 35-46CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
  A review. The use of vanillin as a building block for the chem. industry is discussed in this article. Vanillin is currently one of the only mol. phenolic compds. manufd. on an industrial scale from biomass. It has thus the potential to become a key-intermediate for the synthesis of bio-based polymers, for which arom. monomers are needed to reach good thermo-mech. properties. After a first part dedicated to the current sousing of vanillin, this article focuses on the alk. oxidn. lignin-to-vanillin process, reporting advantages and limits, discusses the various post-depolymn. methods for product isolation and finally examines the outlook for the wider use of vanillin as a key building block for the chem. industry.
27. 27
  Tarabanko, V. E.; Tarabanko, N. Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects. Int. J. Mol. Sci. 2017, 18 (11), 2421, DOI: 10.3390/ijms18112421
  27
  Catalytic oxidation of lignins into the aromatic aldehydes: general process trends and development prospects
  Tarabanko, Valery E.; Tarabanko, Nikolay
  International Journal of Molecular Sciences (2017), 18 (11), 2421/1-2421/29CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)
  A review. This review discusses principal patterns that govern the processes of lignins' catalytic oxidn. into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temp., mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidn. of various lignins are only insignificantly (10-15%) inferior to oxidn. by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process-over 10 mol per mol of obtained vanillin-is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidn. into the arom. aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidn. of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the arom. aldehydes and cellulose are analyzed.
28. 28
  Vangeel, T.; Schutyser, W.; Renders, T.; Sels, B. F. Perspective on Lignin Oxidation: Advances, Challenges, and Future Directions. Top. Curr. Chem. 2018, 376 (4), 30, DOI: 10.1007/s41061-018-0207-2
  28
  Perspective on Lignin Oxidation: Advances, Challenges, and Future Directions
  Vangeel Thijs; Schutyser Wouter; Renders Tom; Sels Bert F
  Topics in current chemistry (Cham) (2018), 376 (4), 30 ISSN:2365-0869.
  Lignin valorization has gained increasing attention over the past decade. Being the world's largest source of renewable aromatics, its valorization could pave the way towards more profitable and more sustainable lignocellulose biorefineries. Many lignin valorization strategies focus on the disassembly of lignin into aromatic monomers, which can serve as platform molecules for the chemical industry. Within this framework, the oxidative conversion of lignin is of great interest because it enables the formation of highly functionalized, valuable compounds. This work provides a brief overview and critical discussion of lignin oxidation research. In the first part, oxidative conversion of lignin models and isolated lignin streams is reviewed. The second part highlights a number of challenges with respect to the substrate, catalyst, and operating conditions, and proposes some future directions regarding the oxidative conversion of lignin.
29. 29
  Aiello, F.; Badolato, M.; Pessina, F.; Sticozzi, C.; Maestrini, V.; Aldinucci, C.; Luongo, L.; Guida, F.; Ligresti, A.; Artese, A. Design and Synthesis of New Transient Receptor Potential Vanilloid Type-1 (TRPV1) Channel Modulators: Identification, Molecular Modeling Analysis, and Pharmacological Characterization of the N -(4-Hydroxy-3-Methoxybenzyl)-4-(Thiophen-2-Yl)butanamid. ACS Chem. Neurosci. 2016, 7 (6), 737– 748, DOI: 10.1021/acschemneuro.5b00333
  29
  Design and Synthesis of New Transient Receptor Potential Vanilloid Type-1 (TRPV1) Channel Modulators: Identification, Molecular Modeling Analysis, and Pharmacological Characterization of the N-(4-Hydroxy-3-methoxybenzyl)-4-(thiophen-2-yl)butanamide, a Small Molecule Endowed with Agonist TRPV1 Activity and Protective Effects against Oxidative Stress
  Aiello, Francesca; Badolato, Mariateresa; Pessina, Federica; Sticozzi, Claudia; Maestrini, Vanessa; Aldinucci, Carlo; Luongo, Livio; Guida, Francesca; Ligresti, Alessia; Artese, Anna; Allara, Marco; Costa, Giosue; Frosini, Maria; Schiano Moriello, Aniello; De Petrocellis, Luciano; Valacchi, Giuseppe; Alcaro, Stefano; Maione, Sabatino; Di Marzo, Vincenzo; Corelli, Federico; Brizzi, Antonella
  ACS Chemical Neuroscience (2016), 7 (6), 737-748CODEN: ACNCDM; ISSN:1948-7193. (American Chemical Society)
  4-(Thiophen-2-yl)butanoic acid was identified as a cyclic substitute of the unsatd. alkyl chain of the natural ligand, capsaicin. Accordingly, a new class of amides was synthesized in good yield and high purity and their mol. recognition against the target was investigated by means of docking expts. followed by mol. dynamics simulations, in order to rationalize their geometrical and thermodn. profiles. The pharmacol. properties of these new compds. were expressed as activation (EC50) and desensitization (IC50) potencies. Several compds. were found to activate TRPV1 channels, and in particular, derivs. I and II behaved as TRPV1 agonists endowed with good efficacy as compared to capsaicin. The most promising compd. I was also evaluated for its protective role against oxidative stress on keratinocytes and differentiated human neuroblastoma cell lines expressing the TRPV1 receptor as well as for its cytotoxicity and analgesic activity in vivo.
30. 30
  Yu, Y.-F.; Huang, Y.-D.; Zhang, C.; Wu, X.-N.; Zhou, Q.; Wu, D.; Wu, Y.; Luo, H.-B. Discovery of Novel Pyrazolopyrimidinone Derivatives as Phosphodiesterase 9A Inhibitors Capable of Inhibiting Butyrylcholinesterase for Treatment of Alzheimer’s Disease. ACS Chem. Neurosci. 2017, 8 (11), 2522– 2534, DOI: 10.1021/acschemneuro.7b00268
  30
  Discovery of Novel Pyrazolopyrimidinone Derivatives as Phosphodiesterase 9A Inhibitors Capable of Inhibiting Butyrylcholinesterase for Treatment of Alzheimer's Disease
  Yu, Yan-Fa; Huang, Ya-Dan; Zhang, Chen; Wu, Xu-Nian; Zhou, Qian; Wu, Deyan; Wu, Yinuo; Luo, Hai-Bin
  ACS Chemical Neuroscience (2017), 8 (11), 2522-2534CODEN: ACNCDM; ISSN:1948-7193. (American Chemical Society)
  Discovery of multitarget directed ligands (MTDLs) targeting at different factors simultaneously to control the complicated pathogenesis of Alzheimer's disease (AD), has become an important research area in recent years. Both PDE9A and BuChE inhibitors could participate in different processes of AD to attenuate neuronal injuries and improve cognitive impairments. However, research on the MTDLs combining the inhibition of PDE9A and BuChE simultaneously has not been reported yet. In this study, a series of novel pyrazolopyrimidinone-rivastigmine hybrids were designed, synthesized, and evaluated in vitro. Most compds. exhibited remarkable inhibitory activities against both PDE9A and BuChE. Compds. I and II showed the best IC50 values against PDE9A (I: 14 nM, II:17 nM, resp.) together with the considerable inhibition against BuChE (IC50, I: 3.3 μM, II: 0.97 μM). Their inhibitory potencies against BuChE were even higher than the anti-AD drug rivastigmine. Worthy to mention is that both showed moderate selectivity for BuChE over AChE. Mol. docking studies revealed their binding patters and explained the influence of configuration and substitutions on the inhibition of PDE9A and BuChE. Furthermore, compds. I and II exhibited negligible toxicity, which made them suitable for the further study of AD in vivo.
31. 31
  Fache, M.; Montérémal, C.; Boutevin, B.; Caillol, S. Amine Hardeners and Epoxy Cross-Linker from Aromatic Renewable Resources. Eur. Polym. J. 2015, 73, 344– 362, DOI: 10.1016/j.eurpolymj.2015.10.032
  31
  Amine hardeners and epoxy cross-linker from aromatic renewable resources
  Fache, Maxence; Monteremal, Camille; Boutevin, Bernard; Caillol, Sylvain
  European Polymer Journal (2015), 73 (), 344-362CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
  Bio-based epoxy thermosets are currently extensively studied. To be industrially relevant, bio-based epoxy formulations must be tailored so that the properties of the resulting thermosets can be conveniently controlled. This can be achieved by choosing the right hardener. Amine hardeners were thus synthesized from potentially bio-sourced vanillin and furfural. These compds. are also arom., an important structural feature to reach good thermo-mech. properties. A tri-functional, vanillin-derived epoxy cross-linker was also synthesized. Multi-functional epoxy monomers can increase the crosslinking d. of the network, which is another convenient way of controlling the final properties. Epoxy thermosets were prepd. from bio-based epoxy monomers and hardeners, and from ref. compds. commonly used in industry. These polymers were characterized and structure-property relationships are discussed.
32. 32
  Yan, T.; Feringa, B. L.; Barta, K. Iron Catalysed Direct Alkylation of Amines with Alcohols. Nat. Commun. 2014, 5, 5602, DOI: 10.1038/ncomms6602
  32
  Iron catalyzed direct alkylation of amines with alcohols
  Yan, Tao; Feringa, Ben L.; Barta, Katalin
  Nature Communications (2014), 5 (), 5602CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
  The selective conversion of carbon-oxygen bonds into carbon-nitrogen bonds to form amines was one of the most important chem. transformations for the prodn. of bulk and fine chems. and pharma intermediates. An atom-economic way of carrying out such C-N bond formations was the direct N-alkylation of simple amines with alcs. by borrowing hydrogen strategy. Transition metal complexes based on precious metals have emerged as suitable catalysts for this transformation; however, the crucial change towards the use of abundant, inexpensive and environmentally friendly metals, in particular iron, has not yet been accomplished. The homogeneous, iron-catalyzed, direct alkylation of amines with alcs. was described. The scope of this new methodol. includes the monoalkylation of anilines and benzyl amines with a wide range of alcs., and the use of diols in the formation of five, six- and seven- membered nitrogen heterocycles, which are privileged structures in numerous pharmaceuticals.
33. 33
  Afanasenko, A.; Elangovan, S.; Stuart, M. C. A.; Bonura, G.; Frusteri, F.; Barta, K. Efficient Nickel-Catalysed: N-Alkylation of Amines with Alcohols. Catal. Sci. Technol. 2018, 8 (21), 5498– 5505, DOI: 10.1039/C8CY01200H
  33
  Efficient nickel-catalysed N-alkylation of amines with alcohols
  Afanasenko, Anastasiia; Elangovan, Saravanakumar; Stuart, Marc C. A.; Bonura, Giuseppe; Frusteri, Francesco; Barta, Katalin
  Catalysis Science & Technology (2018), 8 (21), 5498-5505CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
  In the presence of nickel nanoparticles generated in situ from Ni(cod)2 and KOH, arylamines underwent chemoselective alkylation with alkyl and benzylic alcs. and diols to yield N-monoalkylated arylamines. The morphol. of the nickel nanoparticles generated was characterized by TEM; reactions of arylamines and alkylamines yielded nanoparticles with differing morphologies, consistent with their differences in reactivity. The nanoparticles were used four times in alkylation reactions, but gave products in decreasing yields.
34. 34
  Sun, Z.; Bottari, G.; Afanasenko, A.; Stuart, M. C. A.; Deuss, P. J.; Fridrich, B.; Barta, K. Complete Lignocellulose Conversion with Integrated Catalyst Recycling Yielding Valuable Aromatics and Fuels. Nat. Catal. 2018, 1 (1), 82– 92, DOI: 10.1038/s41929-017-0007-z
  34
  Complete lignocellulose conversion with integrated catalyst recycling yielding valuable aromatics and fuels
  Sun, Zhuohua; Bottari, Giovanni; Afanasenko, Anastasiia; Stuart, Marc C. A.; Deuss, Peter J.; Fridrich, Balint; Barta, Katalin
  Nature Catalysis (2018), 1 (1), 82-92CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
  Lignocellulose, the main component of agricultural and forestry waste, harbours tremendous potential as a renewable starting material for future biorefinery practices. However, this potential remains largely unexploited due to the lack of strategies that derive substantial value from its main constituents. Here, we present a catalytic strategy that is able to transform lignocellulose to a range of attractive products. At the center of our approach is the flexible use of a non-precious metal catalyst in two distinct stages of a lignocellulose conversion process that enables integrated catalyst recycling through full conversion of all process residues. From the lignin, pharmaceutical and polymer building blocks are obtained. Notably, among these pathways are systematic chemo-catalytic methodologies to yield amines from lignin. The (hemi)cellulose-derived aliph. alcs. are transformed to alkanes, achieving excellent total carbon utilization. This work will inspire the development of fully sustainable and economically viable biorefineries.
35. 35
  Hemmingson, J. A.; Leary, G. The Self-Condensation Reactions of the Lignin Model Compounds, Vanillyl and Veratryl Alcohol. Aust. J. Chem. 1980, 33 (4), 917– 925, DOI: 10.1071/CH9800917
  35
  The self-condensation reactions of the lignin model compounds, vanillyl and veratryl alcohol
  Hemmingson, Jacqueline A.; Leary, Gordon
  Australian Journal of Chemistry (1980), 33 (4), 917-25CODEN: AJCHAS; ISSN:0004-9425.
  Self-condensation of vanillyl alc. [498-00-0] and veratryl alc. [93-03-8] as models for lignin in H2O or aq. EtOH resulted in formation of benzyl ether and diphenylmethane structures. The results of the study suggested that condensation reactions between p-hydroxybenzyl alc. structures may also occur in the lignin of long-lived species of plants as the plant ages.
36. 36
  Abbott, J. R.; Patel, P. A.; Howes, J. E.; Akan, D. T.; Kennedy, J. P.; Burns, M. C.; Browning, C. F.; Sun, Q.; Rossanese, O. W.; Phan, J. Discovery of Quinazolines That Activate SOS1-Mediated Nucleotide Exchange on RAS. ACS Med. Chem. Lett. 2018, 9 (9), 941– 946, DOI: 10.1021/acsmedchemlett.8b00296
  36
  Discovery of Quinazolines That Activate SOS1-Mediated Nucleotide Exchange on RAS
  Abbott, Jason R.; Patel, Pratiq A.; Howes, Jennifer E.; Akan, Denis T.; Kennedy, J. Phillip; Burns, Michael C.; Browning, Carrie F.; Sun, Qi; Rossanese, Olivia W.; Phan, Jason; Waterson, Alex G.; Fesik, Stephen W.
  ACS Medicinal Chemistry Letters (2018), 9 (9), 941-946CODEN: AMCLCT; ISSN:1948-5875. (American Chemical Society)
  Proteins in the RAS family are important regulators of cellular signaling and, when mutated, can drive cancer pathogenesis. Despite considerable effort over the last 30 years, RAS proteins have proven to be recalcitrant therapeutic targets. One approach for modulating RAS signaling is to target proteins that interact with RAS, such as the guanine nucleotide exchange factor (GEF) son of sevenless homolog 1 (SOS1). Here, we report hit-to-lead studies on quinazoline-contg. compds. that bind to SOS1 and activate nucleotide exchange on RAS. Using structure-based design, we refined the substituents attached to the quinazoline nucleus and built in addnl. interactions not present in the initial HTS hit. Optimized compds. activate nucleotide exchange at single-digit micromolar concns. in vitro. In HeLa cells, these quinazolines increase the levels of RAS-GTP and cause signaling changes in the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway.
37. 37
  Nakamura, K. Method for producing xylylenediamine. U.S. Patent No. 6,476,269, Nov. 5, 2002.
  There is no corresponding record for this reference.
Supporting Information
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- Detailed spectrometric, chromatographic, and chemical information and ¹H and ¹³C NMR spectral data (PDF)
- sc9b00619_si_001.pdf (2.9 MB)
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Primary Benzylamines by Efficient N-Alkylation of Benzyl Alcohols Using Commercial Ni Catalysts and Easy-to-Handle Ammonia SourcesClick to copy article linkArticle link copied!

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Abstract

Synopsis

Introduction

Experimental Section

Materials

Methods

Representative Procedures

General Procedure 1

General Procedure 2

Control Reaction and Leaching Test

Results and Discussion

Figure 1

Scheme 1

Reaction Network

Optimization of the Reaction Conditions

Figure 2

Catalyst Recycling and Reusability

Primary Benzylamines from Benzyl Alcohols

Toward Biobased and Other Important Benzylamines

Figure 3

Figure 4

Other Biobased and Aliphatic Alcohols

Conclusion

Supporting Information

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Scheme 1

Figure 2

Figure 3

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Primary Benzylamines by Efficient N-Alkylation of Benzyl Alcohols Using Commercial Ni Catalysts and Easy-to-Handle Ammonia Sources
Click to copy article linkArticle link copied!