General and Mild Method for the Synthesis of Polythioesters from Lactone FeedstocksClick to copy article linkArticle link copied!
- McKinley K. PaulMcKinley K. PaulSchool of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, Georgia 30332, United StatesMore by McKinley K. Paul
- Matthew C. RaesideMatthew C. RaesideSchool of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, Georgia 30332, United StatesMore by Matthew C. Raeside
- Will R. Gutekunst*Will R. Gutekunst*(W.R.G.) Email: [email protected]School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, Georgia 30332, United StatesMore by Will R. Gutekunst
Abstract
Polythioesters are attracting increasing interest in applications requiring degradability or recyclability. However, few general methods exist for the synthesis of these polymers. This report presents a fast and versatile method for synthesizing polythioesters from readily available lactone feedstocks. The two-step process begins with the thionation of lactones to thionolactones, followed by the ring-opening polymerization of the thionolactones to polythioesters. Unlike previous methods that rely on harsh reagents to accomplish this transformation, we demonstrate that the mild tetrabutylammonium thioacetate is a competent initiator for polymerization. This method exhibits broad applicability, as demonstrated by the successful polymerizations of an unstrained 17-membered macrocycle and an N-substituted cyclic thionocarbamate. Furthermore, the generality of this scheme enables the synthesis of polythioesters with highly tunable properties, as demonstrated here by the synthesis of a set of polymers with glass transition temperatures spanning 180 °C. Finally, the polythioesters are efficiently depolymerized into the corresponding thiolactones.
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Polythioesters have garnered significant attention in the literature as a promising class of materials with applications in the development of degradable and recyclable polymers. (1−21) Most commonly, polythioesters are synthesized through ring-opening polymerization (ROP) of thiolactones, as demonstrated by Kiesewetter and colleagues. (16) However, this conventional approach suffers from several drawbacks. For example, there are a limited number of commercial reagents that can be transformed into thiolactone monomers in a reasonable number of steps. Additionally, the traditional ROP process demands that the monomer possess sufficient ring strain to drive polymerization. (22) This constraint on monomer design limits the scope of accessible polythioesters. Thus, the chemical diversity in this class of polymers is limited by the few, nongeneral methods for synthesizing thiolactone monomers.
Preparation of polythioesters from lactone starting materials is an ideal solution to this problem, as lactones could provide inexpensive, structurally diverse, and potentially bioderived feedstocks. A promising two-step pathway to accomplish this transformation is the thionation of lactones to thionolactones, followed by a polymerization step, during which the C═S thionolactone monomers isomerize to produce C═O polythioesters. In contrast to the 1,2-addition–elimination mechanism conventionally employed in ROP of thionolactones, (23,24) polymerization of thionolactones to polythioesters occurs via SN2 reaction at the C–O carbon in the lactone ring, expelling a thioacetate chain end for propagation (Figure 1d). (2,25)
Figure 1
Figure 1. Overview of the previous work. (a) Initial work by Endo demonstrating conversion of thionolactones to polythioesters in a polythionoester/polythioester copolymer. (26) (b) Yuan et al.’s recent work showing full selectivity to polythioester products with phosphazene superbase initiator system. (25) (c) Typical 1,2-addition–elimination mechanism expected in ROP of thionolactones which generates polythionoesters. (d) SN2 of thionolactones to generate polythioesters. (e) This work: mild, general, and selective conversion of thionolactones to polythioester followed by depolymerization to thiolactone small molecules.
Endo and co-workers first demonstrated the viability of a thionolactone to polythioester transformation using harsh initiators (such as organolithiums or potassium tert-butoxide). Unfortunately, these conditions resulted in low selectivity of polythioester versus polythionoester products (Figure 1a). (26) However, Endo’s later investigations found that treatment of thionolactones with cationic initiators results exclusively in polythioester products. (27,28) More recently, Hong and co-workers demonstrated that treating thionolactones with phosphazene superbases and diphenylmethanol (or highly electrophilic oxonium salts) achieved complete selectivity to polythioester products with high molecular weights and fair dispersities (Figure 1b). (25,29) Extensive computational studies and end-group analysis via ESI-MS performed by Hong and co-workers showed that polymerization under anionic conditions occurs via propagating thiocarboxylate chain ends. However, only polymerization of five-membered substrates were demonstrated in this recent work, and thus the generality of these transformations was unknown before the current study.
Inspired by these findings, we hypothesized that employing a milder initiator, chemically akin to the propagating thioacetate chain end, would facilitate the same transformation under milder conditions (Figure 1e). To test this hypothesis, 100 equiv of thionovalerolactone 1 was treated with 1 equiv of thioacetic acid and 1 equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in dimethylformamide (DMF) at 5 M. The reaction was heated at 80 °C for 1 h which yielded a sole polymer product with 50% conversion. 13C NMR of the precipitated polymer indicated that the material was completely the polythioester product, as confirmed by comparison to an independently prepared sample of the polythionoester (Figures S3–S6). Prolonging reaction time to 3 h increased conversion to 79%. Interestingly, gas phase density functional theory calculations at the M06-2x/6-311++G** level of theory indicate that the electrophilic orbital involved in the SN2-ROP process is not LUMO but LUMO+1 of the thionolactones (Figures S52 and S53). While the high molecular weight polymer products of the initial test were selectively polythioesters, the crude 1H NMR of our test reaction showed small molecule byproducts around 4.0 ppm, similar to those which Hong and co-workers identified as side products resulting from thionoenolate chemistry. (25) Due to DMF’s dissociation to dimethylamine and carbon monoxide at elevated temperatures, (30) it was hypothesized that switching solvent to dimethylacetamide (DMA) could reduce the thionoenolate-related byproducts. In line with this thought, performing the same reaction in DMA produced fewer byproducts at around 4.0 ppm (Figure S7).
Encouraged by these preliminary results, we further investigated the effect of solvent and concentration on the reaction. Solvents with various characteristics such as polar, nonpolar, hydrogen bond acceptors, and hydrogen bond donors were screened (Tables S2 and S3). However, DMA showed the best performance of any solvent investigated. Next, different initiator systems were evaluated (Table 1). As a control experiment, thionovalerolactone 1 was subjected to DBU alone (Table 1, entry 2). The observed polymerization in this control indicates either that DBU itself is able to directly perform the initiating SN2 to give a zwitterionic ring-opened species or that DBU is able to deprotonate a monomer, generating a thionoenolate species capable of nucleophilic initiation as suggested by Hong and co-workers. (25) To explore the effect of different nucleophiles, benzyl mercaptan and diphenylmethanol were screened in combination with DBU (Table 1, entries 3 and 4). While both systems were found to initiate polymerization, they showed inferior performance to that of the thioacetic acid and DBU combination. As hydrogen bonding was invoked in the exploration of the phosphazene/diphenylmethanol initiation system, (25) hydrogen bond donors were added to the DBU and thioacetic acid system with the goal of increasing polymerization control. Hexafluoroisopropanol (HFIP) and diphenylmethanol were selected for this purpose (Table 1, entries 5 and 6). Both H-bond donors reduced the conversion that took place in 3 h, and neither donor had a positive impact on the dispersity of polymerization. After the thioacetate anion was established as the best performing nucleophile, various bases were investigated.


Conditions: 100 equiv of thionovalerolactone 1, 1 equiv of initiator, DMA, 5 M, 3 h, 80 °C, quenched with excess TFA. (a) Value from ref (31). (b) Value from ref (34). (c) Value from ref (33). (d) Value from ref (35). (e) Value from ref (36). (f) Reaction in toluene, 3 M, 0.5 h. (g) Reaction in toluene, 5 M, 3 h.
Hypothesizing that a sterically bulky countercation could hinder chain transfer and backbiting reactions (Figure S10), several bulky bases were screened in combination with thioacetic acid including Hünig’s base, tBu-P4, an electron-rich aniline, and 2,6-lutidine (Table 1, entries 7–10). Unfortunately, none of these bases showed significantly superior performance compared with DBU and thioacetic acid. tBu-P4, however, did show a slightly decreased dispersity compared to DBU. Along another line of investigation, if the polymerization observed in the control experiment of treating monomer with DBU alone (Table 1, entry 2) was evidence of DBU acting directly as a nucleophilic initiator to generate a zwitterionic chain end, it would stand to reason that using a more nucleophilic amine would improve the polymerization performance. For this purpose, highly nucleophilic quinuclidine was screened (Table 1, entry 11). However, the quinuclidine and thioacetic acid combination showed much lower conversion than the DBU and thioacetic acid combination. This result, combined with the 10 orders of magnitude Ka difference between thioacetic acid and DBU (pKaBH+H2O = 13.5 for DBU compared to pKaBHH2O = 3.4 for thioacetic acid), (31,32) indicates that DBU is acting as a Brønsted base rather than a nucleophile in the thioacetic acid/DBU initiation system. This hypothesis is bolstered by the high conversion and low dispersity resulting from use of the phosphazene super base (pKaBH+DMSO = 30.2 for the phosphazene compared to pKaBH+DMSO = 13.9 for DBU). (31,33) Furthermore, weaker bases, such as Hünig’s base and 2,6-lutidine, both showed lower conversions than DBU, with 2,6-lutidine showing no conversion at all. From these results, it was concluded that stronger bases likely result in higher conversions and lower dispersities due to their production of a higher concentration of the true nucleophilic initiator, the thioacetate anion. To test this theory, the acid–base equilibrium was removed from the equation by testing initiation via addition of the organic soluble tetrabutylammonium thioacetate salt (Table 1, entry 12). Satisfyingly, the thioacetate salt showed the best performance of any initiator screened, matching the conversion of the phosphazene base and thioacetic acid system but with slightly decreased dispersity. Kinetic experiments were also performed (Figure S54), showing first-order behavior for this system.
After optimal polymerization conditions were established, the generality of the reaction was explored (Table 2). A variety of thionolactone monomers were prepared from the corresponding lactones by thionation with either P4S10 or Lawesson’s reagent. The thionolactone monomers were then polymerized with the tetrabutylammonium thioacetate salt in DMA at 5 M/80 °C at a target degree of polymerization (DP) of 200. The homologous series of five (2), six (1), and seven membered (3) unsubstituted thionolactones were initially polymerized. All were polymerized to high conversions with moderate dispersities, demonstrating the generality of the reaction with respect to the ring size. The amount of small molecule thiolactone byproducts, arising from backbiting during polymerization (Figure S10), was greater in the less strained five membered system compared to the more strained six and seven membered systems. However, the thiolactone-producing backbiting reaction could largely be mitigated by decreasing the reaction time. With these results established, monomer 4 was then polymerized. This polymer, P4, was previously unable to be synthesized in a prior report due to the lack of ring strain in the corresponding thiolactone. (22) The synthesis of P4 via the method reported here highlights that the primary driving force of polymerization is the energy released upon C═S to C═O isomerization and not the release of ring strain energy as in ring-opening polymerizations of thiolactones. Thus, removing the consideration of ring strain from monomer design via the synthetic pathway reported here further increases the number and diversity of synthetically accessible polythioesters.

Polymerization conditions: 200 equiv of monomer, 1 equiv of CH3COS NBu4, 5 M DMA, 80 °C, quenched with excess TFA. (a) 200 equiv of monomer, 1 equiv of thioacetic acid, 1 equiv of DBU, DMPU 1 M, 145 °C, 3 h, quenched with excess TFA. (b) 200 equiv of monomer, 1 equiv of CH3COS NBu4, solvent free, 100 °C, 2 h, quenched with excess TFA. (c) Measured via multiangle laser light scattering (MALLS). (d) Value from ref (22). (e) Value from ref (25).
However, although the above examples demonstrate the broad applicability of this reaction, several limitations were found. The phthalide-derived monomer S1 (Figures S11 and S12) was not able to be polymerized, and instead only small molecule isomerization of the thionolactone to the corresponding thiolactone was observed. This outcome is hypothesized to arise from a Thorpe–Ingold-like effect, (37,38) in which the close proximity of the thioacetate and thioester in the ring-opened conformation causes ring closure to become highly favorable. Moreover, monomer S2, a six membered thionolactone methylated at the SN2 carbon, was unreactive in polymerization. This result underscores a predictable limitation in this polymerization scheme: steric hindrance at the SN2 site inhibits the reaction. This result is in line with the previous report, which found that the analogous five membered thionolactone methylated at the SN2 site did not polymerize upon treatment with the phosphazene initiator system. (25)
As polythioesters often show glass transition temperatures below room temperature, (22) several monomers with rigid cyclic groups were targeted with the hopes of achieving glass transition temperatures above room temperature. Gratifyingly, polymers P5 and P6 demonstrated Tg’s well above room temperature, and surprisingly, polymers P3 and P8 also showed Tg’s above room temperature. Among the polymers investigated, P1 possesses a Tg below −80 °C, (22) while P6 exhibited a glass transition temperature of 104 °C. Thus, the polymers reported here encompass a wide range of glass transition temperatures spanning over 180 °C. These results underscore the flexibility and utility of the synthesis pathway developed in this study; the generality of the method enables the synthesis of monomers with a diverse array of structures, offering a versatile approach to producing polythioesters with highly tunable properties.
Additionally, biphenyl monomer 6 showed a low dispersity of 1.2. This surprising result is likely due to the lack of steric hindrance at the SN2 carbon due to the ring conformation of the monomer. (17) By contrast, the conformation of the ring-opened system likely produces a more sterically hindered O–C carbon, reducing the favorability of backbiting or chain transfer reactions which increase dispersity. Macrocyclic monomer 7 also showed a relatively low dispersity of 1.4. Monomer 7 required modified conditions for polymerization (see the Supporting Information for a discussion), with the most important modification being a diluted 1 M polymerization concentration. Thus, the lower dispersity observed in this system is likely due to the lower concentration of chain ends relative to other systems.
While monomers 6 and 7 showed lower dispersities, no system investigated showed dispersities near 1.1 associated with highly controlled polymerization. Thus, possible sources of dispersity broadening were investigated. As thioacetates are generally understudied as both nucleophiles and leaving groups, it was unclear whether chain transfer reactions could occur readily in this system. To test the feasibility of chain transfer, a model thioester, S-dodecyl benzothioate S5, was treated with thioacetic acid and DBU in the previously discussed polymerization conditions (Figure S14). 1H NMR of the reaction after 3 h showed equilibration between the starting materials and the substituted products, S-dodecyl ethanethioate S6 and thiobenzoic acid S7. This result indicates that chain transfer is possible in this system and is likely the primary side reaction which broadens dispersity during polymerization, as small molecule thiolactone products were not observed in high proportions by crude 1H NMR in many of the substrates indicating that backbiting reactions are minimal in most substrates. However, the greater driving force of the SN2 ROP reaction due to the C═S to C═O isomerization makes it unsurprising that propagation is preferred to chain transfer.
To further expand the substrate scope, polymerization of a new heterocyclic system was explored. Endo and co-workers previously reported cationic polymerization of thionocarbamates to the corresponding polythiocarbamates. (39,40) Furthermore, isomerization of thionocarbamate monomer S4 (Figure S11) to the corresponding thiocarbamate has been previously reported when S4 was treated with iodide at 150 °C in xylenes. (41) However, polymerization in analogous conditions (as well as the optimal conditions discussed earlier) was unsuccessful. It was hypothesized that one of three decomposition pathways could be occurring (Figure S13): (1) upon ring-opening, the thiocarbamate anion could irreversibly dissociate to gaseous carbonyl sulfide and an amine; (2) upon ring-opening, gaseous H2S could be expelled concomitant with isocyanate formation; or (3) the thionocarbamate could be deprotonated at the nitrogen to produce a resonance stabilized, non-nucleophilic anion. With these hypotheses in mind, alkylation of the nitrogen to produce monomer 8 was performed to limit decomposition pathways 2 and 3. Monomer 8 was shown to be polymerizable, demonstrating the generality of this polymerization pathway. In principle, other heteroatom systems which can release energy by undergoing X = S to X = O isomerization (such as cyclic thionophosphates) could also be polymerized via this reaction in the future. (42)
Finally, mild depolymerization of the product polythioesters was investigated (Figure 2). Previously, polymer P2 was shown to be amenable to depolymerization. (25) Polythioesters P1, P4, P5, and P6 were successfully converted to the corresponding small molecule thiolactones with very high conversion upon treatment with catalytic quantities of TBD and dodecanethiol relative to the chain end (Figures S15–S18). It is hypothesized that dodecanethiol and TBD initiate a chain scission reaction via trans-thioesterification between dodecanethiol and the polymer backbone. The resulting thiolate chain end then continuously backbites to expel the corresponding small molecule thiolactones until depolymerization is complete. Isolated yields of between 50 and 88% for the corresponding thiolactones were obtained.
Figure 2
Figure 2. Depolymerization of polymers. (a) Example of depolymerization of polymer P6. Conditions: 1 equiv of P6, 20 equiv of TBD/dodecanethiol per chain end, 0.5 M with respect to moles of repeat units, MeCN, 80 °C, 2 h. (b) Comparison of 1H NMR of polymer P6 compared to the thiolactone product 9 produced after depolymerization.
Depolymerization of the polythiocarbamate P8 seemed to produce some of the corresponding small molecule by 1H NMR. The six-membered small molecule thiolactone S8 which arises from depolymerization of P1 has been demonstrated by our group to possess thermodynamics amenable to ROP─hinting at the possibility of employing the synthetic scheme developed here to produce polymers capable of chemical recycling to monomer
Overall, these results demonstrate that polymers with moderately sized repeat units (5–7 atoms) are well-suited for depolymerization, as they produce well-defined small molecule thiolactone products under mild depolymerization conditions. Many of these systems are kinetically trapped in the polymer state and thus are “spring-loaded” to depolymerize when the appropriate chemical trigger is added to the system. Additionally, the established processes of hydrolysis and aminolysis are applicable to polythioesters with any number of atoms in the repeat unit. (2,17) Thus, there are multiple routes available for the conversion of polymers produced via this method to value-added chemicals at their end of life.
In conclusion, the exploration of reaction conditions and substrate scope reported here gives several useful insights into the production of polythioesters from lactone feedstocks. First, organic intuition based on the SN2 mechanism of polymerization illuminates the optimal reaction conditions: high concentration of monomer, polar aprotic environments, and an acid–base equilibrium strongly shifted toward the thioacetate anion. These insights lead to mild, inexpensive, and general conditions to accomplish this transformation. The utility of the method was demonstrated via the synthesis of polymers with glass transition temperatures spanning over 180 °C as well as the extension of this reaction to the polymerization of a thionocarbamate. Finally, the potential of these materials for use in applications requiring upcycling or recycling was demonstrated by mild depolymerization to well-defined small molecule products.
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsmacrolett.4c00556.
Experimental details and characterization data (PDF)
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Acknowledgments
This work was supported by ONR MURI N00014-20-1-2586. M.K.P. was supported by an NSF graduate research fellowship grant DGE-2039655. We acknowledge support from the Organic Materials Characterization Laboratory (OMCL) at GT for use of the shared characterization facility. The authors thank Dr. Ronald A. Smith for the gift of thionolactone monomer 6. We thank Prof. Anthony Engler for the insightful discussions. Computational studies were enabled through research cyberinfrastructure resources and services provided by the Partnership for an Advanced Computing Environment (PACE) at the Georgia Institute of Technology, Atlanta, GA.
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- 9Kricheldorf, H. R.; Schwarz, G. Poly(Thioester)s. Journal of Macromolecular Science, Part A 2007, 44 (6), 625– 649, DOI: 10.1080/10601320701285094Google ScholarThere is no corresponding record for this reference.
- 10Aksakal, S.; Aksakal, R.; Becer, C. R. Thioester Functional Polymers. Polym. Chem. 2018, 9 (36), 4507– 4516, DOI: 10.1039/C8PY00872HGoogle Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsFKqtrvM&md5=7560e6c144ba8124f788d5961e512772Thioester functional polymersAksakal, Suzan; Aksakal, Resat; Becer, C. RemziPolymer Chemistry (2018), 9 (36), 4507-4516CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)A review. Inspired by the uniqueness and ubiquity of thioesters in nature, much attention has been paid to thioester functionalized materials, yielding applications ranging from responsive polymers to bioconjugates and (bio)degradable polymers. This review focuses on various applications of thioesters in polymer science, covering the synthesis and polymn. of thioester contg. monomers, thioester generation via polymn. processes or the presence of thioesters in chain ends, such as initiators or chain transfer agents. Examples of post-polymn. modifications with various compds. to enable modification via pathways such as ligation, amidation or exchange reactions are also presented.
- 11Ura, Y.; Al-Sayah, M.; Montenegro, J.; Beierle, J. M.; Leman, L. J.; Ghadiri, M. R. Dynamic Polythioesters Viaring-Opening Polymerization of 1,4-Thiazine-2,5-Diones. Org. Biomol. Chem. 2009, 7 (14), 2878– 2884, DOI: 10.1039/b903612aGoogle Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXotVegtLo%253D&md5=300d25f038d283c2c1b00fba303ef860Dynamic polythioesters via ring-opening polymerization of 1,4-thiazine-2,5-dionesUra, Yasuyuki; Al-Sayah, Mohammad; Montenegro, Javier; Beierle, John M.; Leman, Luke J.; Ghadiri, M. RezaOrganic & Biomolecular Chemistry (2009), 7 (14), 2878-2884CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)We describe the prepn. and characterization of polythioesters composed of alternating α-amino acid and α-thioglycolic acid residues that undergo dynamic constitutional exchange under mild conditions. The polymers are assembled via reversible ring-opening polymns. of 1,4-thiazine-2,5-diones and related monomers in soln.-phase conditions that do not require the use of transition metal catalysts. Because 1,4-thiazine-2,5-diones can be derived in part from α-amino acids, a variety of side chain functionalized monomers in optically pure forms could readily be accessed. In addn., the resulting polythioesters have the potential for intra- and inter-chain hydrogen bonding, which is known to impart materials properties to other previously studied polyamides. The studies reported here could be useful in advancing a new class of biodegradable polymers and furthermore suggest that dynamic constitutional exchange could be exploited to modify many known synthetic and natural polythioesters.
- 12Bingham, N. M.; Roth, P. J. Degradable Vinyl Copolymers through Thiocarbonyl Addition-Ring-Opening (TARO) Polymerization. Chem. Commun. 2019, 55 (1), 55– 58, DOI: 10.1039/C8CC08287AGoogle Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlSqs7%252FM&md5=70fa915fff1b5456ec66d5591c10a19dDegradable vinyl copolymers through thiocarbonyl addition-ring-opening (TARO) polymerizationBingham, Nathaniel M.; Roth, Peter J.Chemical Communications (Cambridge, United Kingdom) (2019), 55 (1), 55-58CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)The radical copolymn. of the thionolactone dibenzo[c,e]oxepane-5-thione with acrylates, acrylonitrile, and N,N-dimethylacrylamide afforded copolymers contg. a controllable amt. of backbone thioesters which could be selectively cleaved. The process is compatible with RAFT polymn. and promising for the development of advanced degradable polymers.
- 13Yuan, J.; Xiong, W.; Zhou, X.; Zhang, Y.; Shi, D.; Li, Z.; Lu, H. 4-Hydroxyproline-Derived Sustainable Polythioesters: Controlled Ring-Opening Polymerization, Complete Recyclability, and Facile Functionalization. J. Am. Chem. Soc. 2019, 141 (12), 4928– 4935, DOI: 10.1021/jacs.9b00031Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXltFGqtLc%253D&md5=6d37ba4d7a49376712a1ece9b45b7f484-Hydroxyproline-Derived Sustainable Polythioesters: Controlled Ring-Opening Polymerization, Complete Recyclability, and Facile FunctionalizationYuan, Jingsong; Xiong, Wei; Zhou, Xuhao; Zhang, Yi; Shi, Dong; Li, Zichen; Lu, HuaJournal of the American Chemical Society (2019), 141 (12), 4928-4935CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The sustainable prodn. of chem. recyclable polymers presents a significant opportunity to polymer scientists to tackle the growing environmental and energy problems of current petroleum-based plastics. Despite recent advances, however, there are still pressing needs for an expanded horizon of chem. recyclable polymers. Herein, we introduce a new paradigm of biosourced polythioesters (PTEs) with high polymerizability and complete recyclability under mild and economical conditions. The thiolactone monomers with a high ring strain can be easily prepd. in a two-step process from 4-hydroxyproline. Controlled ring-opening polymns. (ROP) using inexpensive and weak bases afford PTEs with high molar masses (Mn) up to 259 kg mol-1 and narrow dispersities generally below 1.15. The properties of PTEs can be readily adjusted by copolymn. and/or pre/post-functionalization on the side chains. Selective and complete depolymns. of the PTEs in dil. soln. at ambient to modest temps. recycle clean monomers. D. functional theory (DFT) calcn. of model reactions provides mechanistic insights and highlights the importance of judicious mol. design. Taken together, the unique ROP/depolymn. chem. of such PTEs may offer a sustainable soln. for creating and manufg. high-value materials such as optical/photochem. plastics, self-immolative polymers, and degradable biomaterials under situations where recycle and reuse are indispensable.
- 14Xiong, W.; Chang, W.; Shi, D.; Yang, L.; Tian, Z.; Wang, H.; Zhang, Z.; Zhou, X.; Chen, E.-Q.; Lu, H. Geminal Dimethyl Substitution Enables Controlled Polymerization of Penicillamine-Derived β-Thiolactones and Reversed Depolymerization. Chem. 2020, 6 (7), 1831– 1843, DOI: 10.1016/j.chempr.2020.06.003Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlyjtbjN&md5=16561ba78810f7a0e6a51b1925207768Geminal Dimethyl Substitution Enables Controlled Polymerization of Penicillamine-Derived β-Thiolactones and Reversed DepolymerizationXiong, Wei; Chang, Wenying; Shi, Dong; Yang, Lijiang; Tian, Ziyou; Wang, Hao; Zhang, Zhengchu; Zhou, Xuhao; Chen, Er-Qiang; Lu, HuaChem (2020), 6 (7), 1831-1843CODEN: CHEMVE; ISSN:2451-9294. (Cell Press)To access infinitely recyclable plastics, one appealing approach is to design thermodynamically neutral systems based on dynamic covalent bond, the (de)polymn. of which can be easily manipulated with low energy cost. Here, we demonstrate the feasibility of this concept via the efficient synthesis of polythioesters PNR-PenTE from penicillamine-derived β-thiolactones and their convenient depolymn. under mild conditions. The gem-di-Me group adjusts the thermodn. of (de)polymn. to near equil., confers better (de)polymn. control by reducing the activity and conformational possibilities of the chain-end thiolate groups, and stabilizes the thioester linkages in the polymer backbone. PNR-PenTE with tailored properties is conveniently accessible by altering the side chains. PNR-PenTE can be recycled to pristine enantiopure β-thiolactones at >95% conversion from minutes to a few hours at room temp. This work highlights the power of judicious mol. design and could greatly facilitate the development of a wide range of recyclable polymers with immense application potentials.
- 15Wang, Y.; Li, M.; Chen, J.; Tao, Y.; Wang, X. O-to-S Substitution Enables Dovetailing Conflicting Cyclizability, Polymerizability, and Recyclability: Dithiolactone vs. Dilactone. Angew. Chem., Int. Ed. 2021, 60 (41), 22547– 22553, DOI: 10.1002/anie.202109767Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitVSjt7fN&md5=24a4240bfacde12962008f51cbecaa82O-to-S Substitution Enables Dovetailing Conflicting Cyclizability, Polymerizability, and Recyclability: Dithiolactone vs. DilactoneWang, Yanchao; Li, Maosheng; Chen, Jinlong; Tao, Youhua; Wang, XianhongAngewandte Chemie, International Edition (2021), 60 (41), 22547-22553CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Developing chem. recyclable polymers represents a greener alternative to landfill and incineration and offers a closed-loop strategy toward a circular materials economy. However, the synthesis of chem. recyclable polymers is still plagued with certain fundamental limitations, including trade-offs between the monomer's cyclizability and polymerizability, as well as between polymer's depolymerizability and properties. Here the authors describe the subtle O-to-S substitution, dithiolactone monomers derived from abundant feedstock α-amino acids can demonstrate appealing chem. properties different from those of dilactone, including accelerated ring closure, augmented kinetics polymerizability, high depolymerizability and selectivity, and thus constitute a unique class of polythioester materials exhibiting controlled mol. wt. (up to 100.5 kDa), atactic yet high crystallinity, structurally diversity, and chem. recyclability. These polythioesters addresses the formidable challenges of developing chem. recyclable polymers by having an unusual set of desired properties, including easy-to-make monomer from ubiquitous feedstock, and high polymerizability, crystallinity and precise tunability of physicochem. performance, as well as high depolymerizability and selectivity. Computational studies explain why O-to-S modification of polymer backbone enables dovetailing desirable, but conflicting, performance into 1 polymer structure.
- 16Bannin, T. J.; Kiesewetter, M. K. Poly(Thioester) by Organocatalytic Ring-Opening Polymerization. Macromolecules 2015, 48 (16), 5481– 5486, DOI: 10.1021/acs.macromol.5b01463Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht12lu7bN&md5=e29503480202fdf93c1e83631b42aeefPoly(thioester) by Organocatalytic Ring-Opening PolymerizationBannin, Timothy J.; Kiesewetter, Matthew K.Macromolecules (Washington, DC, United States) (2015), 48 (16), 5481-5486CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Organocatalysts typically used for the ring-opening polymn. (ROP) of cyclic ester monomers are applied to a thiolactone, ε-thiocaprolactone (tCL). In the absence of an H-bond donor, a nucleophilic polymn. mechanism is proposed. Despite the decreased ability of thioesters and thiols (vs. esters and alcs.) to H-bond, H-bonding organocatalysts-a thiourea in combination with an H-bond accepting base-are also effective for the ROP of tCL. The increased nucleophilicity of thiols (vs. alcs.) is implicated in the increased Mw/Mn of the poly(thiocaprolactone) vs. poly(caprolactone), but deleterious transesterification is suppressed in the presence of a thiourea. The thioester monomer, tCL, is thermodynamically similar to ε-caprolactam but kinetically similar to ε-caprolactone.
- 17Smith, R. A.; Fu, G.; McAteer, O.; Xu, M.; Gutekunst, W. R. Radical Approach to Thioester-Containing Polymers. J. Am. Chem. Soc. 2019, 141 (4), 1446– 1451, DOI: 10.1021/jacs.8b12154Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXpvFKiug%253D%253D&md5=3741381b8e5266bf4ba1230e8a1dc939Radical Approach to Thioester-Containing PolymersSmith, Ronald A.; Fu, Guanyao; McAteer, Owen; Xu, Mizhi; Gutekunst, Will R.Journal of the American Chemical Society (2019), 141 (4), 1446-1451CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new approach to radical ring-opening polymn. is presented that employs a new thionolactone monomer to generate polymers with thioester-contg. backbones. The use of a thiocarbonyl acceptor overcomes longstanding reactivity problems in the field to give complete ring-opening and quant. incorporation into a variety of acrylate polymers. The resulting copolymers readily degrade under hydrolytic conditions, in addn. to cysteine-mediated degrdn. through transthioesterification. The strategy is compatible with reversible addn.-fragmentation chain transfer (RAFT) polymn. and permits the synthesis of block polymers for the prepn. of well-defined macromol. structures.
- 18Worrell, B. T.; Mavila, S.; Wang, C.; Kontour, T. M.; Lim, C.-H.; McBride, M. K.; Musgrave, C. B.; Shoemaker, R.; Bowman, C. N. A User’s Guide to the Thiol-Thioester Exchange in Organic Media: Scope, Limitations, and Applications in Material Science. Polym. Chem. 2018, 9 (36), 4523– 4534, DOI: 10.1039/C8PY01031EGoogle Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsFWgsrbI&md5=919b1dd478836d8561687f25099ce178A user's guide to the thiol-thioester exchange in organic media: scope, limitations, and applications in material scienceWorrell, Brady T.; Mavila, Sudheendran; Wang, Chen; Kontour, Taylor M.; Lim, Chern-Hooi; McBride, Matthew K.; Musgrave, Charles B.; Shoemaker, Richard; Bowman, Christopher N.Polymer Chemistry (2018), 9 (36), 4523-4534CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)The exchange of thiolates and thiols has long been held as a nearly ideal reaction in dynamic covalent chem. The ability for the reaction to proceed smoothly in neutral aq. media has propelled its widespread use in biochem., however, far fewer applications and studies have been directed towards its use in material science which primarily is performed in org. media. Herein, we present the exploration of this dynamic exchange in both small mol. and polymer settings with a wide sampling of thiols, thioesters, org. bases, and nucleophilic catalysts in various org. solvents. Effects of the character of the thiol and thioester, pKa or nucleophilicity of the catalyst, and heat on the reaction were investigated. The mechanism regarding the previously unexplored effectiveness of nucelophilic catalysts, such as quinuclidine or DABCO, to affect the thiol-thioester exchange was also explored. Finally, the use of the thiol-thioester exchange in a network polymer to reduce applied stresses or change shape of the material following polymn. was shown and the ability of basic and nucleophilic catalysts to promote these effects were benchmarked. The influence of polarity in these networks was also explored, with the rate of exchange shown to be easily tuned by the addn. of diluents with varying polarities. Presented here is a so-called "user's guide" to the thiol-thioester exchange; we hope that this guide is instructive to practitioners in the field of material science which seek to utilize the thiol-thioester exchange in both linear and network polymers.
- 19Ghobril, C.; Charoen, K.; Rodriguez, E. K.; Nazarian, A.; Grinstaff, M. W. A Dendritic Thioester Hydrogel Based on Thiol-Thioester Exchange as a Dissolvable Sealant System for Wound Closure. Angew. Chem., Int. Ed. 2013, 52 (52), 14070– 14074, DOI: 10.1002/anie.201308007Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVClsLzF&md5=45364de1d5fa7cd1dfad0bc71d4b04bdA Dendritic Thioester Hydrogel Based on Thiol-Thioester Exchange as a Dissolvable Sealant System for Wound ClosureGhobril, Cynthia; Charoen, Kristie; Rodriguez, Edward K.; Nazarian, Ara; Grinstaff, Mark W.Angewandte Chemie, International Edition (2013), 52 (52), 14070-14074CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The synthesis of a dendritic thioester hydrogel that gels within seconds because of the formation of multiple thioester linkages between the thiol residues in the dendron and a PEG macromer was demonstrated. The hydrogel binds to human skin, was biocompatible and sealed a punctured bovine jugular vein.
- 20Orrillo, A. G.; Furlan, R. L. E. Sulfur in Dynamic Covalent Chemistry. Angew. Chem. 2022, 134 (26), e202201168 DOI: 10.1002/ange.202201168Google ScholarThere is no corresponding record for this reference.
- 21Kiel, G. R.; Lundberg, D. J.; Prince, E.; Husted, K. E. L.; Johnson, A. M.; Lensch, V.; Li, S.; Shieh, P.; Johnson, J. A. Cleavable Comonomers for Chemically Recyclable Polystyrene: A General Approach to Vinyl Polymer Circularity. J. Am. Chem. Soc. 2022, 144 (28), 12979– 12988, DOI: 10.1021/jacs.2c05374Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhs1SisL7M&md5=ed0bba713cfa55eaa5ba10b38a10b74bCleavable Comonomers for Chemically Recyclable Polystyrene: A General Approach to Vinyl Polymer CircularityKiel, Gavin R.; Lundberg, David J.; Prince, Elisabeth; Husted, Keith E. L.; Johnson, Alayna M.; Lensch, Valerie; Li, Sipei; Shieh, Peyton; Johnson, Jeremiah A.Journal of the American Chemical Society (2022), 144 (28), 12979-12988CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Many common polymers, esp. vinyl polymers, are inherently difficult to chem. recycle and are environmentally persistent. The introduction of low levels of cleavable comonomer additives into existing vinyl polymn. processes could facilitate the prodn. of chem. deconstructable and recyclable variants with otherwise equiv. properties. Here, we report thionolactones that serve as cleavable comonomer additives for the chem. deconstruction and recycling of vinyl polymers prepd. through free radical polymn., using polystyrene (PS) as a model example. Deconstructable PS of different molar masses (~ 20-300 kDa) bearing varied amts. of statistically incorporated thioester backbone linkages (2.5-55 mol %) can be selectively depolymd. to yield well-defined thiol-terminated fragments (<10 kDa) that are suitable for oxidative repolymn. to generate recycled PS of nearly identical molar mass to the parent material, in good yields (80-95%). A theor. model is provided to generalize this molar mass memory effect. Notably, the thermomech. properties of deconstructable PS bearing 2.5 mol % of cleavable linkages and its recycled product are similar to those of virgin PS. The additives were also shown to be effective for deconstruction of a cross-linked styrenic copolymer and deconstruction and repolymn. of a polyacrylate, suggesting that cleavable comonomers may offer a general approach toward circularity of many vinyl (co)polymers.
- 22Stellmach, K. A.; Paul, M. K.; Xu, M.; Su, Y.-L.; Fu, L.; Toland, A. R.; Tran, H.; Chen, L.; Ramprasad, R.; Gutekunst, W. R. Modulating Polymerization Thermodynamics of Thiolactones Through Substituent and Heteroatom Incorporation. ACS Macro Lett. 2022, 11 (7), 895– 901, DOI: 10.1021/acsmacrolett.2c00319Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhs1yks73F&md5=c798d701ba34f5f9cb266e2d6b747207Modulating Polymerization Thermodynamics of Thiolactones Through Substituent and Heteroatom IncorporationStellmach, Kellie A.; Paul, McKinley K.; Xu, Mizhi; Su, Yong-Liang; Fu, Liangbing; Toland, Aubrey R.; Tran, Huan; Chen, Lihua; Ramprasad, Rampi; Gutekunst, Will R.ACS Macro Letters (2022), 11 (7), 895-901CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)A central challenge in the development of next-generation sustainable materials is to design polymers that can easily revert back to their monomeric starting material through chem. recycling to monomer (CRM). An emerging monomer class that displays efficient CRM are thiolactones, which exhibit rapid rates of polymn. and depolymn. This report details the polymn. thermodn. for a series of thiolactone monomers through systematic changes to substitution patterns and sulfur heteroatom incorporation. Addnl., computational studies highlight the importance of conformation in modulating the enthalpy of polymn., leading to monomers that display high conversions to polymer at near-ambient temps., while maintaining low ceiling temps. (Tc). Specifically, the combination of a highly neg. enthalpy (-19.3 kJ/mol) and entropy (-58.4 J/(mol·K)) of polymn. allows for a monomer whose equil. polymn. conversion is very sensitive to temp.
- 23Datta, P. P.; Kiesewetter, M. K. Controlled Organocatalytic Ring-Opening Polymerization of ε-Thionocaprolactone. Macromolecules 2016, 49 (3), 774– 780, DOI: 10.1021/acs.macromol.6b00136Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvVWgsL4%253D&md5=0196a9a8126b74f0bf6f4ae6526c216cControlled Organocatalytic Ring-Opening Polymerization of ε-ThionocaprolactoneDatta, Partha P.; Kiesewetter, Matthew K.Macromolecules (Washington, DC, United States) (2016), 49 (3), 774-780CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)For the first time, the controlled ring-opening polymn. (ROP) of ε-thionocaprolactone (tnCL) was conducted. The organocatalytic ROP of tnCL occurs without carbonyl scrambling, leading to homopolymer of poly(ε-thionocaprolactone) (PtnCL). The ROP by base catalysts alone is proposed to proceed via a nucleophilic mechanism, while the addn. of an H-bond donating thiourea (TU) is shown to provide excellent reaction control. The increased reaction control provided by the TU occurs in the virtual absence of binding between tnCL and TU, and a mechanistic account for this observation is discussed. The monomer ring strain is measured and found to be similar to δ-valerolactone (VL). Copolymers with VL are synthesized, and the resulting anal. of the copolymer materials properties provides the only known phys. characterizations of poly(thio(no)ester-co-ester)s.
- 24Kalana, U. L. D. I.; Datta, P. P.; Hewawasam, R. S.; Kiesewetter, E. T.; Kiesewetter, M. K. Organocatalytic Ring-Opening Polymerization of Thionolactones: Anything O Can Do, S Can Do Better. Polym. Chem. 2021, 12 (10), 1458– 1464, DOI: 10.1039/D0PY01393EGoogle ScholarThere is no corresponding record for this reference.
- 25Yuan, P.; Sun, Y.; Xu, X.; Luo, Y.; Hong, M. Towards High-Performance Sustainable Polymers via Isomerization-Driven Irreversible Ring-Opening Polymerization of Five-Membered Thionolactones. Nat. Chem. 2022, 14 (3), 294– 303, DOI: 10.1038/s41557-021-00817-9Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXisFyhsbnL&md5=10e8e13abd0b4423515aaca742f1d47eTowards high-performance sustainable polymers via isomerization-driven irreversible ring-opening polymerization of five-membered thionolactonesYuan, Pengjun; Sun, Yangyang; Xu, Xiaowei; Luo, Yi; Hong, MiaoNature Chemistry (2022), 14 (3), 294-303CODEN: NCAHBB; ISSN:1755-4330. (Nature Portfolio)The development of sustainable polymers that possess useful material properties competitive with existing petroleum-derived polymers is a crucial goal but remains a formidable challenge for polymer science. Here we demonstrate that irreversible ring-opening polymn. (IROP) of biomass-derived five-membered thionolactones is an effective and robust strategy for the polymn. of non-strained five-membered rings-these polymns. are commonly thermodynamically forbidden under ambient conditions, at industrially relevant temps. of 80-100°C. Computational studies reveal that the selective IROP of these thionolactones is thermodynamically driven by S/O isomerization during the ring-opening process. IROP of γ-thionobutyrolactone, a representative non-strained thionolactone, affords a sustainable polymer from renewable resources that possesses external-stimuli-triggered degradability. This poly(thiolactone) also exhibits high performance, with its key thermal and mech. properties comparing well to those of com. petroleum-based low-d. polyethylene. This IROP strategy will enable conversion of five-membered lactones, generally unachievable by other polymn. methods, into sustainable polymers with a range of potential applications.
- 26Sanda, F.; Jirakanjana, D.; Hitomi, M.; Endo, T. Anionic Ring-Opening Polymerization of ε-Thionocaprolactone. Macromolecules 1999, 32, 8010, DOI: 10.1021/ma990977sGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmvFCqtbk%253D&md5=dcc79126e72db682bb5424bcebba580eAnionic Ring-Opening Polymerization of ε-ThionocaprolactoneSanda, Fumio; Jirakanjana, Duangjai; Hitomi, Masakatsu; Endo, TakeshiMacromolecules (1999), 32 (24), 8010-8014CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Anionic ring-opening polymn. of ε-thionocaprolactone was examd. When organolithium compds., Grignard reagents or t-BuOLi were used as initiators, the poly(thiocarboxylic-O-ester) was selectively formed. When t-BuOK or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were used, the corresponding poly(thiocarboxylic-S-ester) was predominantly formed. The monomer conversion and Mn of the polymer increased with the polymn. temp. Increasing the polymn. time resulted in a decrease in polymer yield and Mn. Polymn. in THF proceeded faster than in toluene. Cyclic dimer formation was obsd. in THF.
- 27Sanda, F.; Jirakanjana, D.; Hitomi, M.; Endo, T. Cationic Ring-Opening Polymerization of ϵ-Thionocaprolactone: Selective Formation of Polythioester. J. Polym. Sci., Part A: Polym. Chem. 2000, 38 (22), 4057– 4061, DOI: 10.1002/1099-0518(20001115)38:22<4057::AID-POLA50>3.0.CO;2-8Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXnsl2lu70%253D&md5=115f097ae0f65019f2c32eb6626001dfCationic ring-opening polymerization of ε-thionocaprolactone: selective formation of polythioesterSanda, Fumio; Jirakanjana, Duangjai; Hitomi, Masakatsu; Endo, TakeshiJournal of Polymer Science, Part A: Polymer Chemistry (2000), 38 (22), 4057-4061CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)Cationic ring-opening polymn. of ε-thionocaprolactone was examd. The corresponding polythioester with the no.-av. mol. wt. (Mn) of 57,000 was obtained in the polymn. with 1 mol % of BF3·OEt2 as an initiator in CH2Cl2 at 28°C for 5 h with quant. monomer conversion. The Mn of the polymer increased with the solvent polarity and monomer-to-initiator ratio. No polymn. took place below -30°C, and the monomer conversion and Mn of the polymer increased with the temp. in the range of -15 to 28°C. The increase of initial monomer concn. was effective to improve the monomer conversion and the Mn of the obtained polymer.
- 28Kikuchi, H.; Tsubokawa, N.; Endo, T. First Example of Cationic Ring-Opening Polymerization of γ-Thionobutyrolactone. Chem. Lett. 2005, 34 (3), 376– 377, DOI: 10.1246/cl.2005.376Google ScholarThere is no corresponding record for this reference.
- 29Xia, Y.; Yuan, P.; Zhang, Y.; Sun, Y.; Hong, M. Converting Non-Strained γ-Valerolactone and Derivatives into Sustainable Polythioesters via Isomerization-Driven Cationic Ring-Opening Polymerization of Thionolactone Intermediate. Angew. Chem., Int. Ed. 2023, 62 (14), e202217812 DOI: 10.1002/anie.202217812Google ScholarThere is no corresponding record for this reference.
- 30Petersen, T. P.; Larsen, A. F.; Ritzén, A.; Ulven, T. Continuous Flow Nucleophilic Aromatic Substitution with Dimethylamine Generated in Situ by Decomposition of DMF. J. Org. Chem. 2013, 78 (8), 4190– 4195, DOI: 10.1021/jo400390tGoogle Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktFKgtLk%253D&md5=836620da83e1298146d5a8813a61dd3eContinuous Flow Nucleophilic Aromatic Substitution with Dimethylamine Generated in Situ by Decomposition of DMFPetersen, Trine P.; Larsen, Anders F.; Ritzen, Andreas; Ulven, TrondJournal of Organic Chemistry (2013), 78 (8), 4190-4195CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A safe, practical, and scalable continuous flow protocol for the in situ generation of dimethylamine from DMF followed by nucleophilic arom. substitution of a broad range of arom. and heteroarom. halides is reported.
- 31Kütt, A.; Selberg, S.; Kaljurand, I.; Tshepelevitsh, S.; Heering, A.; Darnell, A.; Kaupmees, K.; Piirsalu, M.; Leito, I. pKa Values in Organic Chemistry - Making Maximum Use of the Available Data. Tetrahedron Lett. 2018, 59 (42), 3738– 3748, DOI: 10.1016/j.tetlet.2018.08.054Google ScholarThere is no corresponding record for this reference.
- 32Janssen, M. J. Thiolo, Thiono and Dithio Acids and Esters. In Carboxylic Acids and Esters (1969); John Wiley & Sons, Ltd.: 1969; pp 705– 764.Google ScholarThere is no corresponding record for this reference.
- 33Schwesinger, R.; Schlemper, H.; Hasenfratz, C.; Willaredt, J.; Dambacher, T.; Breuer, T.; Ottaway, C.; Fletschinger, M.; Boele, J.; Fritz, H.; Putzas, D.; Rotter, H. W.; Bordwell, F. G.; Satish, A. V.; Ji, G.-Z.; Peters, E.-M.; Peters, K.; von Schnering, H. G.; Walz, L. Extremely Strong, Uncharged Auxiliary Bases; Monomeric and Polymer-Supported Polyaminophosphazenes (P2-P5). Liebigs Annalen 1996, 1996 (7), 1055– 1081, DOI: 10.1002/jlac.199619960705Google ScholarThere is no corresponding record for this reference.
- 34Lepore, S. D.; Khoram, A.; Bromfield, D. C.; Cohn, P.; Jairaj, V.; Silvestri, M. A. Studies on the Manganese-Mediated Isomerization of Alkynyl Carbonyls to Allenyl Carbonyls. J. Org. Chem. 2005, 70 (18), 7443– 7446, DOI: 10.1021/jo051040uGoogle Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXntVCgsr0%253D&md5=cc0d907b8c8285000866444254cd043bStudies on the manganese-mediated isomerization of alkynyl carbonyls to allenyl carbonylsLepore, Salvatore D.; Khoram, Anita; Bromfield, Deborah C.; Cohn, Pamela; Jairaj, Vinod; Silvestri, Maximilian A.Journal of Organic Chemistry (2005), 70 (18), 7443-7446CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A study of the role of base in the isomerization of Mn-coordinated conjugated alkynyl carbonyls to the corresponding allenyl carbonyls is described. The use of phosphine additives indicates that Mn requires a ligand prior to isomerization with amine bases. Amine bases were also examd. for their efficacy in this isomerization reaction revealing a strong dependence on pKa. By contrast, K tert-butoxide led to rapid isomerization in the absence of added Mn ligand.
- 35Izzet, G.; Zeng, X.; Akdas, H.; Marrot, J.; Reinaud, O. Drastic Effects of the Second Coordination Sphere on Neutral vs. Anionic Guest Binding to a Biomimetic Cu(II) Center Embedded in a Calix[6]Aza-Cryptand. Chem. Commun. 2007, (8), 810– 812, DOI: 10.1039/B613564AGoogle ScholarThere is no corresponding record for this reference.
- 36Benoit, R. L.; Lefebvre, D.; Fréchette, M. Basicity of 1,8-Bis(Dimethylamino)Naphthalene and 1,4-Diazabicyclo[2.2.2]Octane in Water and Dimethylsulfoxide. Can. J. Chem. 1987, 65 (5), 996– 1001, DOI: 10.1139/v87-170Google ScholarThere is no corresponding record for this reference.
- 37Beesley, R. M.; Ingold, C. K.; Thorpe, J. F. CXIX.─The Formation and Stability of Spiro-Compounds. Part I. Spiro-Compounds from Cyclohexane. J. Chem. Soc., Trans. 1915, 107 (0), 1080– 1106, DOI: 10.1039/CT9150701080Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaC2MXhvVGiuw%253D%253D&md5=de4306fddc79f71809a8556525abc983Formation and stability of spiro-compounds. I. Spiro-compounds from cyclohexanoBeesley, Richard M.; Ingold, Christopher K.; Thorpe, Jocelyn F.Journal of the Chemical Society, Transactions (1915), 107 (), 1080-1106CODEN: JCHTA3; ISSN:0368-1645.A series of investigations has been undertaken with the object of ascertaining "the effect produced by the alteration of the tetrahedral angle consequent on ring formation, on the formation and stability of a 2nd ring joined to the existing ring by a quaternary C atom common to both." The hypothesis was advanced that the angle formed by the 2 side chains attached to any 1 C atom of the cyclohexane ring will be altered in proportion to any change in angle between those valencies which participate in ring formation; i. e., the groups attached to 2 side chains emanating from the same C atom of a cyclohexane deriv., type (I), will be closer together than in a corresponding compd. having the open chain structure, type (II). Expts. show that this hypothesis is probably correct. For example a trans-spiro-acid, derived from a compd. of type (I) is more stable than trans-caronic acid, derived from a compd. of type (II). The above hypothesis and another untenable one are presented and discussed in some detail and diagrammatically represented by showing the effect of "strain" on the angles between the valencies (represented by the apices of an inscribed tetrahedron) of a (spherical) C atom. The bromination of CH2(CH2)4C(CH2CO2H)2 by means of PBr5 and Br led to the formation of a mixt. containing an acid product, probably C5H10>C(CHBrCO2H)(CH2CO2Et) (A), and a neutral product (B). The latter was shown to be a mixt. of cis-diethyl α,α'-dibromocyclohexane-1,1-diacetate (C) (not obtained in the pure state) and the trans-lactone (D), C5H10>C.CH(CO2Et).O.CO.CHBr, prisms from petroleum or alc., m. 96°, b20 225-30°. (D) was sepd. from the mixt. (B) by the addition of an equal vol. of petroleum (b. 60-70°) and was also synthesized by boiling (C) with C5H5N [whereby only the trans-form of (C) was converted into (D)] or by distg. (C), whereby both the cis- and trans-forms were converted. The isomeric cis-lactone (D'), microneedles, m. 69-70°, was formed in 25% yield upon distg. (C) from which (D) had been previously removed by means of C5H5N. α-Hydroxycyclohexane-1,1-diacetic acid lactone (E), C5H10>C.CH(CO2H).O.CO.CH2, b13 240-1°, crystg. after long standing and seeding, microneedles, m. 91-2° (silver salt, amorphous), was formed from (A) by the action of boiling Na2CO3. The free acid (F) corresponding to (E) could not be isolated and was found to be stable only in the form of its salts. The amorphous silver salt and cryst. sodium salt of (F) were prepd. The dianilide of (F), C5H10>C(CH2CONHPh)CH(OH)CONHPh, needles, m. 97°. The aniline salt of (E), silky needles, m. 104°. When (A) was added to boiling concd. KOH and the reaction mixt. cooled and acidified, trans-cyclohexane-spiro-cyclopropane-1,2-dicarboxylic acid (G), C5H10>C.CH(CO2H).CHCO2H, flattened needles, m. 237°, was formed. Its silver salt sepd. in the form of a cryst. powder: its dianilide, needles, m. 292°. The filtrate from (G) after extn. with Et2O and fractionation under reduced pressure yielded the cis-isomer (H) of (G), needles, m. 198°, more readily formed by distg. (G) which is first converted into the anhydride (J), C5H10>C.CH.CO.O.CO.CH, needles, m. 102°, which on treatment with alkali and subsequent acidification yields (H). (J) was also readily prepd. by the interaction of (H) and AcCl, whereas (G) is not acted upon by this reagent. The anilic acid, C5H10>C.CH(CO2H).CHCONHPh, derived from (J), small needles,m. 207° (decompn.); the corresponding anil, m. 119°. When heated in a sealed tube with 50% concd. HCl at 180° for 5 hrs., (H) is partially reconverted into (G). On attempting to replace the Br in (D) by an OH group, by means of moist Ag2O, ethyl α-hydroxycyclohexane-1,1-diacetate lactone, C5H10> C.CH2CO.O.CHCO2Et, b21 210°, was obtained and yielded (E) on hydrolysis. The following hydrolysis products were formed when (D) was treated with boiling 15% aq. NaOH:C5H10>C:CHCO2H (K), m. 92° (identical with Wallach's acid as shown by the formation of the dibromide, m. 135-6°; ref. not given), and the trans-lactonic acid of α,α'-dihydroxycyclohexane-1,1-diacetic acid (L), C5H10>C.CH(OH).CO.O.CHCO2H.H2O, prisms, 100°, anhydrous, m. 145°. (D') when subjected to a similar hydrolysis gave rise to a mixt. of (K), the cis-isomer (M) of (L), prisms, m. 168°, and cyclohexane-spiro-cyclopropanol-2,3-dicarboxylic acid (N), C5H10>C.C(OH)(CO2H).CHCO2H, pearly plates, m. 217°. Boiling alc. KOH, reacting with (D), yielded (K), (L) and (N). The action of 64% aq. KOH on (D) gave rise to a mixt. of (L), (N) and Δ1-cyclohexeneacetic acid, (O), CH2(CH2)3CH:C.CH2CO2H, m. 38° (identical with Wallach's compd.; also quant. formed by boiling (K) with 64% KOH, thus indicating that it was a byproduct in the above reaction). The Et ester of (O), b25 118-2° (cf. Auwers and Ellinger, C. A. 6, 1147). A similar reaction between 64% KOH and (D') gave rise to (O), (M) and (N). (K) and (N) were sepd. by treatment with dry Et2O in which (N) is insol. (L) was ordinarily sepd. from hydrolysis mixts. by esterifying and fractionating the ethyl ester, b25 206-10°. The following derivs. of (L) are described: disodium salt, cryst.; disilver salt, powder; aniline salt, microcrystals, m. 133-4°; dianilide, C5H10>C[CH(OH)CONHPh]2, short needles, m. 169°. (L) does not react with AcCl, is not reduced by AgOH, and when heated with H2O in a sealed tube or when distd., passes into (M). The isolation of (M) was effected by esterifying hydrolysis mixts. and collecting the fraction of highest b. p., which was subsequently hydrolyzed with HCl. (M) was readily acetylated. The following derivs. of (M) were prepd.: disilver salt; dianilide, needles, m. 169° (not identical with the dianilide derived from (L)); acetate, C5H10>CH(OAc).CO.O.CHCO2H, m. 156° (silver salt of the acetate, cryst. powder). The spiro-acid (N), which like (L) could not be acetylated, which is not converted into the lactone on heating and is otherwise stable, gave rise to the following compds.: silver salt, cryst. powder; anilide, needles, m. 202°. Concd. H2SO4 acting upon (L) at 95-100°, gave rise to small amts. of cyclohexane-spiro-cyclopentanone, oil (forming a semicarbazone, needles, m. 175°), and an unidentified compd., m. 105°. When heated with an equal amt. of H2O in a sealed tube at 240° for 0.5 hr., (L) yielded the lactonic acid of α-hydroxy-α'-cyclohexan-1-olsuccinic acid, C5H10>C.O.CO.CH(OH).CHCO2H, cubical prisms, m. 131°, whose disodium salt, disilver salt and aniline salt, m. 123°, were prepd.
- 38Sammes, P. G.; Weller, D. J. Steric Promotion of Ring Formation. Synthesis 1995, 1995 (10), 1205– 1222, DOI: 10.1055/s-1995-4099Google ScholarThere is no corresponding record for this reference.
- 39Nagai, A.; Ochiai, B.; Endo, T. Cationic Ring-Opening Polymerization of Optically Active N-Substituted Cyclic Thiourethanes. Macromolecules 2004, 37 (20), 7538– 7542, DOI: 10.1021/ma049114bGoogle Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXntVOrtbg%253D&md5=a965555fa54b8dffd727951837da3c09Cationic ring-opening polymerization of optically active N-substituted cyclic thiourethanesNagai, Atsushi; Ochiai, Bungo; Endo, TakeshiMacromolecules (2004), 37 (20), 7538-7542CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)N-substituted cyclic thiourethanes, i.e., [4(S)-(methoxycarbonyl)-N-benzyl-1,3-oxazolidine-2-thione (BnSL), 4(S)-(methoxycarbonyl)-N-benzoyl-1,3-oxazolidine-2-thione (BzSL), and 4(S)-(methoxycarbonyl)-N-acetyl-1,3-oxazolidine-2-thione (AcSL)], were synthesized from L-serine Me ester hydrochloride and were polymd. using Me trifluoromethanesulfonate to obtain the corresponding well-defined polythiourethanes. The mol. wt. of the polymers can be controlled by the ratio of the monomers to the initiator and the mol. wt. distributions are narrow (Mw/Mn < 1.15), similar to the previously reported polymn. of a cyclic thiourethane [4(S)-(methoxycarbonyl)-1,3-oxazolidine-2-thione (SL)]. The polymn. rates are on the order of SL > BnSL > BzSL > AcSL, which agrees well with the nucleophilicity of the thiocarbonyl moieties of the monomers (SL, BnSL BzSL, and AcSL). The Cotton effects in the CD spectra of the polymers from the N-substituted monomers exhibit an almost inverse shape with that of poly(SL) and the sp. rotations' signs also inversed, suggesting the idea that poly(SL) and N-substituted polymers take different high order structures.
- 40Nagai, D.; Sato, M.; Ochiai, B.; Endo, T. Controlled Cationic Ring-Opening Polymerization of a Six-Membered Cyclic Thiourethane. Macromolecules 2004, 37 (10), 3523– 3525, DOI: 10.1021/ma049839fGoogle Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXivFKqu7g%253D&md5=4bb16826aed0b5334f6d3e6764e72128Controlled cationic ring-opening polymerization of a six-membered cyclic thiourethaneNagai, Daisuke; Sato, Masato; Ochiai, Bungo; Endo, TakeshiMacromolecules (2004), 37 (10), 3523-3525CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A well-defined polythiourethane was obtained by controlled cationic ring-opening polymn. of 3-benzyl-1,3-oxazinane-2-thione. Control of mol. wt. was also achieved by using dithiocarbamate as a terminator. The polymer showed high refractive index and thermal stability. Exptl. details on 3-benzyl-1,3-oxazinane-2-thione monomer characterization are given in the supporting information.
- 41Awheda, I.; Saygili, N.; Garner, A. C.; Wallis, J. D. Activation and Regioselectivity of Five-Membered Cyclic Thionocarbamates to Nucleophilic Attack. RSC Adv. 2013, 3 (47), 24997– 25009, DOI: 10.1039/c3ra41074aGoogle ScholarThere is no corresponding record for this reference.
- 42Liu, Y.; Bejjanki, N. K.; Jiang, W.; Zhao, Y.; Wang, L.; Sun, X.; Tang, X.; Liu, H.; Wang, Y. Controlled Syntheses of Well-Defined Poly(Thionophosphoester)s That Undergo Peroxide-Triggered Degradation. Macromolecules 2019, 52 (11), 4306– 4316, DOI: 10.1021/acs.macromol.9b00061Google ScholarThere is no corresponding record for this reference.
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- Shaoqiu Zheng, Shu‐Sen Chen, Yang‐Yang Li, Minjian Liao, Xuhui Liang, Ke Li, Xiaopeng Li, Jinming Hu, Dian‐Feng Chen. Monomer Design Enables Mechanistic Mapping of Anionic Ring‐Opening Polymerization of Aromatic Thionolactones. Angewandte Chemie 2025, 494 https://doi.org/10.1002/ange.202500581
- Shaoqiu Zheng, Shu‐Sen Chen, Yang‐Yang Li, Minjian Liao, Xuhui Liang, Ke Li, Xiaopeng Li, Jinming Hu, Dian‐Feng Chen. Monomer Design Enables Mechanistic Mapping of Anionic Ring‐Opening Polymerization of Aromatic Thionolactones. Angewandte Chemie International Edition 2025, 494 https://doi.org/10.1002/anie.202500581
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Abstract
Figure 1
Figure 1. Overview of the previous work. (a) Initial work by Endo demonstrating conversion of thionolactones to polythioesters in a polythionoester/polythioester copolymer. (26) (b) Yuan et al.’s recent work showing full selectivity to polythioester products with phosphazene superbase initiator system. (25) (c) Typical 1,2-addition–elimination mechanism expected in ROP of thionolactones which generates polythionoesters. (d) SN2 of thionolactones to generate polythioesters. (e) This work: mild, general, and selective conversion of thionolactones to polythioester followed by depolymerization to thiolactone small molecules.
Figure 2
Figure 2. Depolymerization of polymers. (a) Example of depolymerization of polymer P6. Conditions: 1 equiv of P6, 20 equiv of TBD/dodecanethiol per chain end, 0.5 M with respect to moles of repeat units, MeCN, 80 °C, 2 h. (b) Comparison of 1H NMR of polymer P6 compared to the thiolactone product 9 produced after depolymerization.
References
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- 1Li, H.; Guillaume, S. M.; Carpentier, J. F. Polythioesters Prepared by Ring-Opening Polymerization of Cyclic Thioesters and Related Monomers. Chemistry - An Asian Journal 2022, 17 (17), e202200641 DOI: 10.1002/asia.202200641There is no corresponding record for this reference.
- 2Narmon, A. S.; van Slagmaat, C. A. M. R.; De Wildeman, S. M. A.; Dusselier, M. Sustainable Polythioesters via Thio(No)Lactones: Monomer Synthesis, Ring-Opening Polymerization, End-of-Life Considerations, and Industrial Perspectives. ChemSusChem 2023, 16 (9), e202202276 DOI: 10.1002/cssc.202202276There is no corresponding record for this reference.
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- 5Overberger, C. G.; Weise, J. K. Anionic Ring-Opening Polymerization of Thiolactones. J. Am. Chem. Soc. 1968, 90 (13), 3533– 3537, DOI: 10.1021/ja01015a0435https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXkt1Oqsb4%253D&md5=6beda11f21295284e6e01aae626605f6Anionic ring-opening polymerization of thiolactonesOverberger, Charles G.; Weise, Jurgen K.Journal of the American Chemical Society (1968), 90 (13), 3533-7CODEN: JACSAT; ISSN:0002-7863.Thiepan-2-one (ε-thiocaprolactone) was prepd. by cyclization of 6-mercaptohexanoic acid and polymd. by a base-catalyzed ring-opening reaction to a linear poly(thiol ester). Poly(ε-thiocaprolactone) is cryst. and has a high mol. wt. (intrinsic viscosity, 0.5-1.0 dl./g. in CHCl3). Its cryst. m.p. is 105°; it has a 2nd-order transition at + 19° and is sol. in several common solvents, esp. in partially halogenated hydrocarbons. When oriented by drawing, it has a fiber period of 17.8 A., which corresponds to the length of 2 extended thiol ester repeating units (14 atoms in the backbone). Thian-2-one (δ-thiovalerolactone) can also be converted into a cryst. polymer, but thiolan-2-one (γ-thiobutyrolactone) does not react under these conditions. The reactivity of the thiolactones toward polymn. catalysts is, therefore, dependent on ring size in a manner analogous to the behavior of lactones, but different from that of lactams.
- 6Mavila, S.; Worrell, B. T.; Culver, H. R.; Goldman, T. M.; Wang, C.; Lim, C.-H.; Domaille, D. W.; Pattanayak, S.; McBride, M. K.; Musgrave, C. B.; Bowman, C. N. Dynamic and Responsive DNA-like Polymers. J. Am. Chem. Soc. 2018, 140 (42), 13594– 13598, DOI: 10.1021/jacs.8b091056https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvV2rs7%252FI&md5=d42477bc7e922a77652d547706d529fbDynamic and Responsive DNA-like PolymersMavila, Sudheendran; Worrell, Brady T.; Culver, Heidi R.; Goldman, Trevor M.; Wang, Chen; Lim, Chern-Hooi; Domaille, Dylan W.; Pattanayak, Sankha; McBride, Matthew K.; Musgrave, Charles B.; Bowman, Christopher N.Journal of the American Chemical Society (2018), 140 (42), 13594-13598CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The synthesis of thiolactone monomers that mimic natural nucleosides and engage in robust ring opening polymns. (ROP) is herein described. As each repeat unit contains a thioester functional group, dynamic rearrangement of the polymer is feasible via thiol-thioester exchange, demonstrated here by depolymn. of the polymers and coalescing of two polymers of different mol. wt. or chem. compn. This approach constitutes the first step toward a platform that enables for the routine synthesis of sequence controlled polymers via dynamic template directed synthesis.
- 7Galanopoulo, P.; Gil, N.; Gigmes, D.; Lefay, C.; Guillaneuf, Y.; Lages, M.; Nicolas, J.; Lansalot, M.; D’Agosto, F. One-Step Synthesis of Degradable Vinylic Polymer-Based Latexes via Aqueous Radical Emulsion Polymerization. Angew. Chem., Int. Ed. 2022, 61 (15), e202117498 DOI: 10.1002/anie.2021174987https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XkvFShsb0%253D&md5=f1e4a803a116e539a4badd7e5ee3c5c5One-Step Synthesis of Degradable Vinylic Polymer-Based Latexes via Aqueous Radical Emulsion PolymerizationGalanopoulo, Paul; Gil, Noemie; Gigmes, Didier; Lefay, Catherine; Guillaneuf, Yohann; Lages, Maelle; Nicolas, Julien; Lansalot, Muriel; D'Agosto, FranckAngewandte Chemie, International Edition (2022), 61 (15), e202117498CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Aq. emulsion copolymns. of dibenzo[c,e]oxepane-5-thione (DOT) were performed with Bu acrylate (BA), styrene (S) and a combination of both. In all cases, stable latexes were obtained in less than two hours under conventional conditions; that is in the presence of sodium dodecyl sulfate (SDS) used as surfactant and potassium persulfate (KPS) as initiator. A limited soly. of DOT in BA was obsd. compared to S, yielding to a more homogeneous integration of DOT units in the PS latex. In both cases, the copolymer could be easily degraded under basic conditions. Emulsion terpolymn. between DOT, BA and S allowed us to produce stable latexes not only composed of degradable chains but also featuring a broad range of glass transition temps.
- 8Shi, C.; McGraw, M. L.; Li, Z.-C.; Cavallo, L.; Falivene, L.; Chen, E. Y.-X. High-Performance Pan-Tactic Polythioesters with Intrinsic Crystallinity and Chemical Recyclability. Science Advances 2020, 6 (34), eabc0495 DOI: 10.1126/sciadv.abc0495There is no corresponding record for this reference.
- 9Kricheldorf, H. R.; Schwarz, G. Poly(Thioester)s. Journal of Macromolecular Science, Part A 2007, 44 (6), 625– 649, DOI: 10.1080/10601320701285094There is no corresponding record for this reference.
- 10Aksakal, S.; Aksakal, R.; Becer, C. R. Thioester Functional Polymers. Polym. Chem. 2018, 9 (36), 4507– 4516, DOI: 10.1039/C8PY00872H10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsFKqtrvM&md5=7560e6c144ba8124f788d5961e512772Thioester functional polymersAksakal, Suzan; Aksakal, Resat; Becer, C. RemziPolymer Chemistry (2018), 9 (36), 4507-4516CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)A review. Inspired by the uniqueness and ubiquity of thioesters in nature, much attention has been paid to thioester functionalized materials, yielding applications ranging from responsive polymers to bioconjugates and (bio)degradable polymers. This review focuses on various applications of thioesters in polymer science, covering the synthesis and polymn. of thioester contg. monomers, thioester generation via polymn. processes or the presence of thioesters in chain ends, such as initiators or chain transfer agents. Examples of post-polymn. modifications with various compds. to enable modification via pathways such as ligation, amidation or exchange reactions are also presented.
- 11Ura, Y.; Al-Sayah, M.; Montenegro, J.; Beierle, J. M.; Leman, L. J.; Ghadiri, M. R. Dynamic Polythioesters Viaring-Opening Polymerization of 1,4-Thiazine-2,5-Diones. Org. Biomol. Chem. 2009, 7 (14), 2878– 2884, DOI: 10.1039/b903612a11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXotVegtLo%253D&md5=300d25f038d283c2c1b00fba303ef860Dynamic polythioesters via ring-opening polymerization of 1,4-thiazine-2,5-dionesUra, Yasuyuki; Al-Sayah, Mohammad; Montenegro, Javier; Beierle, John M.; Leman, Luke J.; Ghadiri, M. RezaOrganic & Biomolecular Chemistry (2009), 7 (14), 2878-2884CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)We describe the prepn. and characterization of polythioesters composed of alternating α-amino acid and α-thioglycolic acid residues that undergo dynamic constitutional exchange under mild conditions. The polymers are assembled via reversible ring-opening polymns. of 1,4-thiazine-2,5-diones and related monomers in soln.-phase conditions that do not require the use of transition metal catalysts. Because 1,4-thiazine-2,5-diones can be derived in part from α-amino acids, a variety of side chain functionalized monomers in optically pure forms could readily be accessed. In addn., the resulting polythioesters have the potential for intra- and inter-chain hydrogen bonding, which is known to impart materials properties to other previously studied polyamides. The studies reported here could be useful in advancing a new class of biodegradable polymers and furthermore suggest that dynamic constitutional exchange could be exploited to modify many known synthetic and natural polythioesters.
- 12Bingham, N. M.; Roth, P. J. Degradable Vinyl Copolymers through Thiocarbonyl Addition-Ring-Opening (TARO) Polymerization. Chem. Commun. 2019, 55 (1), 55– 58, DOI: 10.1039/C8CC08287A12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlSqs7%252FM&md5=70fa915fff1b5456ec66d5591c10a19dDegradable vinyl copolymers through thiocarbonyl addition-ring-opening (TARO) polymerizationBingham, Nathaniel M.; Roth, Peter J.Chemical Communications (Cambridge, United Kingdom) (2019), 55 (1), 55-58CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)The radical copolymn. of the thionolactone dibenzo[c,e]oxepane-5-thione with acrylates, acrylonitrile, and N,N-dimethylacrylamide afforded copolymers contg. a controllable amt. of backbone thioesters which could be selectively cleaved. The process is compatible with RAFT polymn. and promising for the development of advanced degradable polymers.
- 13Yuan, J.; Xiong, W.; Zhou, X.; Zhang, Y.; Shi, D.; Li, Z.; Lu, H. 4-Hydroxyproline-Derived Sustainable Polythioesters: Controlled Ring-Opening Polymerization, Complete Recyclability, and Facile Functionalization. J. Am. Chem. Soc. 2019, 141 (12), 4928– 4935, DOI: 10.1021/jacs.9b0003113https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXltFGqtLc%253D&md5=6d37ba4d7a49376712a1ece9b45b7f484-Hydroxyproline-Derived Sustainable Polythioesters: Controlled Ring-Opening Polymerization, Complete Recyclability, and Facile FunctionalizationYuan, Jingsong; Xiong, Wei; Zhou, Xuhao; Zhang, Yi; Shi, Dong; Li, Zichen; Lu, HuaJournal of the American Chemical Society (2019), 141 (12), 4928-4935CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The sustainable prodn. of chem. recyclable polymers presents a significant opportunity to polymer scientists to tackle the growing environmental and energy problems of current petroleum-based plastics. Despite recent advances, however, there are still pressing needs for an expanded horizon of chem. recyclable polymers. Herein, we introduce a new paradigm of biosourced polythioesters (PTEs) with high polymerizability and complete recyclability under mild and economical conditions. The thiolactone monomers with a high ring strain can be easily prepd. in a two-step process from 4-hydroxyproline. Controlled ring-opening polymns. (ROP) using inexpensive and weak bases afford PTEs with high molar masses (Mn) up to 259 kg mol-1 and narrow dispersities generally below 1.15. The properties of PTEs can be readily adjusted by copolymn. and/or pre/post-functionalization on the side chains. Selective and complete depolymns. of the PTEs in dil. soln. at ambient to modest temps. recycle clean monomers. D. functional theory (DFT) calcn. of model reactions provides mechanistic insights and highlights the importance of judicious mol. design. Taken together, the unique ROP/depolymn. chem. of such PTEs may offer a sustainable soln. for creating and manufg. high-value materials such as optical/photochem. plastics, self-immolative polymers, and degradable biomaterials under situations where recycle and reuse are indispensable.
- 14Xiong, W.; Chang, W.; Shi, D.; Yang, L.; Tian, Z.; Wang, H.; Zhang, Z.; Zhou, X.; Chen, E.-Q.; Lu, H. Geminal Dimethyl Substitution Enables Controlled Polymerization of Penicillamine-Derived β-Thiolactones and Reversed Depolymerization. Chem. 2020, 6 (7), 1831– 1843, DOI: 10.1016/j.chempr.2020.06.00314https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlyjtbjN&md5=16561ba78810f7a0e6a51b1925207768Geminal Dimethyl Substitution Enables Controlled Polymerization of Penicillamine-Derived β-Thiolactones and Reversed DepolymerizationXiong, Wei; Chang, Wenying; Shi, Dong; Yang, Lijiang; Tian, Ziyou; Wang, Hao; Zhang, Zhengchu; Zhou, Xuhao; Chen, Er-Qiang; Lu, HuaChem (2020), 6 (7), 1831-1843CODEN: CHEMVE; ISSN:2451-9294. (Cell Press)To access infinitely recyclable plastics, one appealing approach is to design thermodynamically neutral systems based on dynamic covalent bond, the (de)polymn. of which can be easily manipulated with low energy cost. Here, we demonstrate the feasibility of this concept via the efficient synthesis of polythioesters PNR-PenTE from penicillamine-derived β-thiolactones and their convenient depolymn. under mild conditions. The gem-di-Me group adjusts the thermodn. of (de)polymn. to near equil., confers better (de)polymn. control by reducing the activity and conformational possibilities of the chain-end thiolate groups, and stabilizes the thioester linkages in the polymer backbone. PNR-PenTE with tailored properties is conveniently accessible by altering the side chains. PNR-PenTE can be recycled to pristine enantiopure β-thiolactones at >95% conversion from minutes to a few hours at room temp. This work highlights the power of judicious mol. design and could greatly facilitate the development of a wide range of recyclable polymers with immense application potentials.
- 15Wang, Y.; Li, M.; Chen, J.; Tao, Y.; Wang, X. O-to-S Substitution Enables Dovetailing Conflicting Cyclizability, Polymerizability, and Recyclability: Dithiolactone vs. Dilactone. Angew. Chem., Int. Ed. 2021, 60 (41), 22547– 22553, DOI: 10.1002/anie.20210976715https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitVSjt7fN&md5=24a4240bfacde12962008f51cbecaa82O-to-S Substitution Enables Dovetailing Conflicting Cyclizability, Polymerizability, and Recyclability: Dithiolactone vs. DilactoneWang, Yanchao; Li, Maosheng; Chen, Jinlong; Tao, Youhua; Wang, XianhongAngewandte Chemie, International Edition (2021), 60 (41), 22547-22553CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Developing chem. recyclable polymers represents a greener alternative to landfill and incineration and offers a closed-loop strategy toward a circular materials economy. However, the synthesis of chem. recyclable polymers is still plagued with certain fundamental limitations, including trade-offs between the monomer's cyclizability and polymerizability, as well as between polymer's depolymerizability and properties. Here the authors describe the subtle O-to-S substitution, dithiolactone monomers derived from abundant feedstock α-amino acids can demonstrate appealing chem. properties different from those of dilactone, including accelerated ring closure, augmented kinetics polymerizability, high depolymerizability and selectivity, and thus constitute a unique class of polythioester materials exhibiting controlled mol. wt. (up to 100.5 kDa), atactic yet high crystallinity, structurally diversity, and chem. recyclability. These polythioesters addresses the formidable challenges of developing chem. recyclable polymers by having an unusual set of desired properties, including easy-to-make monomer from ubiquitous feedstock, and high polymerizability, crystallinity and precise tunability of physicochem. performance, as well as high depolymerizability and selectivity. Computational studies explain why O-to-S modification of polymer backbone enables dovetailing desirable, but conflicting, performance into 1 polymer structure.
- 16Bannin, T. J.; Kiesewetter, M. K. Poly(Thioester) by Organocatalytic Ring-Opening Polymerization. Macromolecules 2015, 48 (16), 5481– 5486, DOI: 10.1021/acs.macromol.5b0146316https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht12lu7bN&md5=e29503480202fdf93c1e83631b42aeefPoly(thioester) by Organocatalytic Ring-Opening PolymerizationBannin, Timothy J.; Kiesewetter, Matthew K.Macromolecules (Washington, DC, United States) (2015), 48 (16), 5481-5486CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Organocatalysts typically used for the ring-opening polymn. (ROP) of cyclic ester monomers are applied to a thiolactone, ε-thiocaprolactone (tCL). In the absence of an H-bond donor, a nucleophilic polymn. mechanism is proposed. Despite the decreased ability of thioesters and thiols (vs. esters and alcs.) to H-bond, H-bonding organocatalysts-a thiourea in combination with an H-bond accepting base-are also effective for the ROP of tCL. The increased nucleophilicity of thiols (vs. alcs.) is implicated in the increased Mw/Mn of the poly(thiocaprolactone) vs. poly(caprolactone), but deleterious transesterification is suppressed in the presence of a thiourea. The thioester monomer, tCL, is thermodynamically similar to ε-caprolactam but kinetically similar to ε-caprolactone.
- 17Smith, R. A.; Fu, G.; McAteer, O.; Xu, M.; Gutekunst, W. R. Radical Approach to Thioester-Containing Polymers. J. Am. Chem. Soc. 2019, 141 (4), 1446– 1451, DOI: 10.1021/jacs.8b1215417https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXpvFKiug%253D%253D&md5=3741381b8e5266bf4ba1230e8a1dc939Radical Approach to Thioester-Containing PolymersSmith, Ronald A.; Fu, Guanyao; McAteer, Owen; Xu, Mizhi; Gutekunst, Will R.Journal of the American Chemical Society (2019), 141 (4), 1446-1451CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new approach to radical ring-opening polymn. is presented that employs a new thionolactone monomer to generate polymers with thioester-contg. backbones. The use of a thiocarbonyl acceptor overcomes longstanding reactivity problems in the field to give complete ring-opening and quant. incorporation into a variety of acrylate polymers. The resulting copolymers readily degrade under hydrolytic conditions, in addn. to cysteine-mediated degrdn. through transthioesterification. The strategy is compatible with reversible addn.-fragmentation chain transfer (RAFT) polymn. and permits the synthesis of block polymers for the prepn. of well-defined macromol. structures.
- 18Worrell, B. T.; Mavila, S.; Wang, C.; Kontour, T. M.; Lim, C.-H.; McBride, M. K.; Musgrave, C. B.; Shoemaker, R.; Bowman, C. N. A User’s Guide to the Thiol-Thioester Exchange in Organic Media: Scope, Limitations, and Applications in Material Science. Polym. Chem. 2018, 9 (36), 4523– 4534, DOI: 10.1039/C8PY01031E18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsFWgsrbI&md5=919b1dd478836d8561687f25099ce178A user's guide to the thiol-thioester exchange in organic media: scope, limitations, and applications in material scienceWorrell, Brady T.; Mavila, Sudheendran; Wang, Chen; Kontour, Taylor M.; Lim, Chern-Hooi; McBride, Matthew K.; Musgrave, Charles B.; Shoemaker, Richard; Bowman, Christopher N.Polymer Chemistry (2018), 9 (36), 4523-4534CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)The exchange of thiolates and thiols has long been held as a nearly ideal reaction in dynamic covalent chem. The ability for the reaction to proceed smoothly in neutral aq. media has propelled its widespread use in biochem., however, far fewer applications and studies have been directed towards its use in material science which primarily is performed in org. media. Herein, we present the exploration of this dynamic exchange in both small mol. and polymer settings with a wide sampling of thiols, thioesters, org. bases, and nucleophilic catalysts in various org. solvents. Effects of the character of the thiol and thioester, pKa or nucleophilicity of the catalyst, and heat on the reaction were investigated. The mechanism regarding the previously unexplored effectiveness of nucelophilic catalysts, such as quinuclidine or DABCO, to affect the thiol-thioester exchange was also explored. Finally, the use of the thiol-thioester exchange in a network polymer to reduce applied stresses or change shape of the material following polymn. was shown and the ability of basic and nucleophilic catalysts to promote these effects were benchmarked. The influence of polarity in these networks was also explored, with the rate of exchange shown to be easily tuned by the addn. of diluents with varying polarities. Presented here is a so-called "user's guide" to the thiol-thioester exchange; we hope that this guide is instructive to practitioners in the field of material science which seek to utilize the thiol-thioester exchange in both linear and network polymers.
- 19Ghobril, C.; Charoen, K.; Rodriguez, E. K.; Nazarian, A.; Grinstaff, M. W. A Dendritic Thioester Hydrogel Based on Thiol-Thioester Exchange as a Dissolvable Sealant System for Wound Closure. Angew. Chem., Int. Ed. 2013, 52 (52), 14070– 14074, DOI: 10.1002/anie.20130800719https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVClsLzF&md5=45364de1d5fa7cd1dfad0bc71d4b04bdA Dendritic Thioester Hydrogel Based on Thiol-Thioester Exchange as a Dissolvable Sealant System for Wound ClosureGhobril, Cynthia; Charoen, Kristie; Rodriguez, Edward K.; Nazarian, Ara; Grinstaff, Mark W.Angewandte Chemie, International Edition (2013), 52 (52), 14070-14074CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The synthesis of a dendritic thioester hydrogel that gels within seconds because of the formation of multiple thioester linkages between the thiol residues in the dendron and a PEG macromer was demonstrated. The hydrogel binds to human skin, was biocompatible and sealed a punctured bovine jugular vein.
- 20Orrillo, A. G.; Furlan, R. L. E. Sulfur in Dynamic Covalent Chemistry. Angew. Chem. 2022, 134 (26), e202201168 DOI: 10.1002/ange.202201168There is no corresponding record for this reference.
- 21Kiel, G. R.; Lundberg, D. J.; Prince, E.; Husted, K. E. L.; Johnson, A. M.; Lensch, V.; Li, S.; Shieh, P.; Johnson, J. A. Cleavable Comonomers for Chemically Recyclable Polystyrene: A General Approach to Vinyl Polymer Circularity. J. Am. Chem. Soc. 2022, 144 (28), 12979– 12988, DOI: 10.1021/jacs.2c0537421https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhs1SisL7M&md5=ed0bba713cfa55eaa5ba10b38a10b74bCleavable Comonomers for Chemically Recyclable Polystyrene: A General Approach to Vinyl Polymer CircularityKiel, Gavin R.; Lundberg, David J.; Prince, Elisabeth; Husted, Keith E. L.; Johnson, Alayna M.; Lensch, Valerie; Li, Sipei; Shieh, Peyton; Johnson, Jeremiah A.Journal of the American Chemical Society (2022), 144 (28), 12979-12988CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Many common polymers, esp. vinyl polymers, are inherently difficult to chem. recycle and are environmentally persistent. The introduction of low levels of cleavable comonomer additives into existing vinyl polymn. processes could facilitate the prodn. of chem. deconstructable and recyclable variants with otherwise equiv. properties. Here, we report thionolactones that serve as cleavable comonomer additives for the chem. deconstruction and recycling of vinyl polymers prepd. through free radical polymn., using polystyrene (PS) as a model example. Deconstructable PS of different molar masses (~ 20-300 kDa) bearing varied amts. of statistically incorporated thioester backbone linkages (2.5-55 mol %) can be selectively depolymd. to yield well-defined thiol-terminated fragments (<10 kDa) that are suitable for oxidative repolymn. to generate recycled PS of nearly identical molar mass to the parent material, in good yields (80-95%). A theor. model is provided to generalize this molar mass memory effect. Notably, the thermomech. properties of deconstructable PS bearing 2.5 mol % of cleavable linkages and its recycled product are similar to those of virgin PS. The additives were also shown to be effective for deconstruction of a cross-linked styrenic copolymer and deconstruction and repolymn. of a polyacrylate, suggesting that cleavable comonomers may offer a general approach toward circularity of many vinyl (co)polymers.
- 22Stellmach, K. A.; Paul, M. K.; Xu, M.; Su, Y.-L.; Fu, L.; Toland, A. R.; Tran, H.; Chen, L.; Ramprasad, R.; Gutekunst, W. R. Modulating Polymerization Thermodynamics of Thiolactones Through Substituent and Heteroatom Incorporation. ACS Macro Lett. 2022, 11 (7), 895– 901, DOI: 10.1021/acsmacrolett.2c0031922https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhs1yks73F&md5=c798d701ba34f5f9cb266e2d6b747207Modulating Polymerization Thermodynamics of Thiolactones Through Substituent and Heteroatom IncorporationStellmach, Kellie A.; Paul, McKinley K.; Xu, Mizhi; Su, Yong-Liang; Fu, Liangbing; Toland, Aubrey R.; Tran, Huan; Chen, Lihua; Ramprasad, Rampi; Gutekunst, Will R.ACS Macro Letters (2022), 11 (7), 895-901CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)A central challenge in the development of next-generation sustainable materials is to design polymers that can easily revert back to their monomeric starting material through chem. recycling to monomer (CRM). An emerging monomer class that displays efficient CRM are thiolactones, which exhibit rapid rates of polymn. and depolymn. This report details the polymn. thermodn. for a series of thiolactone monomers through systematic changes to substitution patterns and sulfur heteroatom incorporation. Addnl., computational studies highlight the importance of conformation in modulating the enthalpy of polymn., leading to monomers that display high conversions to polymer at near-ambient temps., while maintaining low ceiling temps. (Tc). Specifically, the combination of a highly neg. enthalpy (-19.3 kJ/mol) and entropy (-58.4 J/(mol·K)) of polymn. allows for a monomer whose equil. polymn. conversion is very sensitive to temp.
- 23Datta, P. P.; Kiesewetter, M. K. Controlled Organocatalytic Ring-Opening Polymerization of ε-Thionocaprolactone. Macromolecules 2016, 49 (3), 774– 780, DOI: 10.1021/acs.macromol.6b0013623https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvVWgsL4%253D&md5=0196a9a8126b74f0bf6f4ae6526c216cControlled Organocatalytic Ring-Opening Polymerization of ε-ThionocaprolactoneDatta, Partha P.; Kiesewetter, Matthew K.Macromolecules (Washington, DC, United States) (2016), 49 (3), 774-780CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)For the first time, the controlled ring-opening polymn. (ROP) of ε-thionocaprolactone (tnCL) was conducted. The organocatalytic ROP of tnCL occurs without carbonyl scrambling, leading to homopolymer of poly(ε-thionocaprolactone) (PtnCL). The ROP by base catalysts alone is proposed to proceed via a nucleophilic mechanism, while the addn. of an H-bond donating thiourea (TU) is shown to provide excellent reaction control. The increased reaction control provided by the TU occurs in the virtual absence of binding between tnCL and TU, and a mechanistic account for this observation is discussed. The monomer ring strain is measured and found to be similar to δ-valerolactone (VL). Copolymers with VL are synthesized, and the resulting anal. of the copolymer materials properties provides the only known phys. characterizations of poly(thio(no)ester-co-ester)s.
- 24Kalana, U. L. D. I.; Datta, P. P.; Hewawasam, R. S.; Kiesewetter, E. T.; Kiesewetter, M. K. Organocatalytic Ring-Opening Polymerization of Thionolactones: Anything O Can Do, S Can Do Better. Polym. Chem. 2021, 12 (10), 1458– 1464, DOI: 10.1039/D0PY01393EThere is no corresponding record for this reference.
- 25Yuan, P.; Sun, Y.; Xu, X.; Luo, Y.; Hong, M. Towards High-Performance Sustainable Polymers via Isomerization-Driven Irreversible Ring-Opening Polymerization of Five-Membered Thionolactones. Nat. Chem. 2022, 14 (3), 294– 303, DOI: 10.1038/s41557-021-00817-925https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXisFyhsbnL&md5=10e8e13abd0b4423515aaca742f1d47eTowards high-performance sustainable polymers via isomerization-driven irreversible ring-opening polymerization of five-membered thionolactonesYuan, Pengjun; Sun, Yangyang; Xu, Xiaowei; Luo, Yi; Hong, MiaoNature Chemistry (2022), 14 (3), 294-303CODEN: NCAHBB; ISSN:1755-4330. (Nature Portfolio)The development of sustainable polymers that possess useful material properties competitive with existing petroleum-derived polymers is a crucial goal but remains a formidable challenge for polymer science. Here we demonstrate that irreversible ring-opening polymn. (IROP) of biomass-derived five-membered thionolactones is an effective and robust strategy for the polymn. of non-strained five-membered rings-these polymns. are commonly thermodynamically forbidden under ambient conditions, at industrially relevant temps. of 80-100°C. Computational studies reveal that the selective IROP of these thionolactones is thermodynamically driven by S/O isomerization during the ring-opening process. IROP of γ-thionobutyrolactone, a representative non-strained thionolactone, affords a sustainable polymer from renewable resources that possesses external-stimuli-triggered degradability. This poly(thiolactone) also exhibits high performance, with its key thermal and mech. properties comparing well to those of com. petroleum-based low-d. polyethylene. This IROP strategy will enable conversion of five-membered lactones, generally unachievable by other polymn. methods, into sustainable polymers with a range of potential applications.
- 26Sanda, F.; Jirakanjana, D.; Hitomi, M.; Endo, T. Anionic Ring-Opening Polymerization of ε-Thionocaprolactone. Macromolecules 1999, 32, 8010, DOI: 10.1021/ma990977s26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmvFCqtbk%253D&md5=dcc79126e72db682bb5424bcebba580eAnionic Ring-Opening Polymerization of ε-ThionocaprolactoneSanda, Fumio; Jirakanjana, Duangjai; Hitomi, Masakatsu; Endo, TakeshiMacromolecules (1999), 32 (24), 8010-8014CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)Anionic ring-opening polymn. of ε-thionocaprolactone was examd. When organolithium compds., Grignard reagents or t-BuOLi were used as initiators, the poly(thiocarboxylic-O-ester) was selectively formed. When t-BuOK or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were used, the corresponding poly(thiocarboxylic-S-ester) was predominantly formed. The monomer conversion and Mn of the polymer increased with the polymn. temp. Increasing the polymn. time resulted in a decrease in polymer yield and Mn. Polymn. in THF proceeded faster than in toluene. Cyclic dimer formation was obsd. in THF.
- 27Sanda, F.; Jirakanjana, D.; Hitomi, M.; Endo, T. Cationic Ring-Opening Polymerization of ϵ-Thionocaprolactone: Selective Formation of Polythioester. J. Polym. Sci., Part A: Polym. Chem. 2000, 38 (22), 4057– 4061, DOI: 10.1002/1099-0518(20001115)38:22<4057::AID-POLA50>3.0.CO;2-827https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXnsl2lu70%253D&md5=115f097ae0f65019f2c32eb6626001dfCationic ring-opening polymerization of ε-thionocaprolactone: selective formation of polythioesterSanda, Fumio; Jirakanjana, Duangjai; Hitomi, Masakatsu; Endo, TakeshiJournal of Polymer Science, Part A: Polymer Chemistry (2000), 38 (22), 4057-4061CODEN: JPACEC; ISSN:0887-624X. (John Wiley & Sons, Inc.)Cationic ring-opening polymn. of ε-thionocaprolactone was examd. The corresponding polythioester with the no.-av. mol. wt. (Mn) of 57,000 was obtained in the polymn. with 1 mol % of BF3·OEt2 as an initiator in CH2Cl2 at 28°C for 5 h with quant. monomer conversion. The Mn of the polymer increased with the solvent polarity and monomer-to-initiator ratio. No polymn. took place below -30°C, and the monomer conversion and Mn of the polymer increased with the temp. in the range of -15 to 28°C. The increase of initial monomer concn. was effective to improve the monomer conversion and the Mn of the obtained polymer.
- 28Kikuchi, H.; Tsubokawa, N.; Endo, T. First Example of Cationic Ring-Opening Polymerization of γ-Thionobutyrolactone. Chem. Lett. 2005, 34 (3), 376– 377, DOI: 10.1246/cl.2005.376There is no corresponding record for this reference.
- 29Xia, Y.; Yuan, P.; Zhang, Y.; Sun, Y.; Hong, M. Converting Non-Strained γ-Valerolactone and Derivatives into Sustainable Polythioesters via Isomerization-Driven Cationic Ring-Opening Polymerization of Thionolactone Intermediate. Angew. Chem., Int. Ed. 2023, 62 (14), e202217812 DOI: 10.1002/anie.202217812There is no corresponding record for this reference.
- 30Petersen, T. P.; Larsen, A. F.; Ritzén, A.; Ulven, T. Continuous Flow Nucleophilic Aromatic Substitution with Dimethylamine Generated in Situ by Decomposition of DMF. J. Org. Chem. 2013, 78 (8), 4190– 4195, DOI: 10.1021/jo400390t30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktFKgtLk%253D&md5=836620da83e1298146d5a8813a61dd3eContinuous Flow Nucleophilic Aromatic Substitution with Dimethylamine Generated in Situ by Decomposition of DMFPetersen, Trine P.; Larsen, Anders F.; Ritzen, Andreas; Ulven, TrondJournal of Organic Chemistry (2013), 78 (8), 4190-4195CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A safe, practical, and scalable continuous flow protocol for the in situ generation of dimethylamine from DMF followed by nucleophilic arom. substitution of a broad range of arom. and heteroarom. halides is reported.
- 31Kütt, A.; Selberg, S.; Kaljurand, I.; Tshepelevitsh, S.; Heering, A.; Darnell, A.; Kaupmees, K.; Piirsalu, M.; Leito, I. pKa Values in Organic Chemistry - Making Maximum Use of the Available Data. Tetrahedron Lett. 2018, 59 (42), 3738– 3748, DOI: 10.1016/j.tetlet.2018.08.054There is no corresponding record for this reference.
- 32Janssen, M. J. Thiolo, Thiono and Dithio Acids and Esters. In Carboxylic Acids and Esters (1969); John Wiley & Sons, Ltd.: 1969; pp 705– 764.There is no corresponding record for this reference.
- 33Schwesinger, R.; Schlemper, H.; Hasenfratz, C.; Willaredt, J.; Dambacher, T.; Breuer, T.; Ottaway, C.; Fletschinger, M.; Boele, J.; Fritz, H.; Putzas, D.; Rotter, H. W.; Bordwell, F. G.; Satish, A. V.; Ji, G.-Z.; Peters, E.-M.; Peters, K.; von Schnering, H. G.; Walz, L. Extremely Strong, Uncharged Auxiliary Bases; Monomeric and Polymer-Supported Polyaminophosphazenes (P2-P5). Liebigs Annalen 1996, 1996 (7), 1055– 1081, DOI: 10.1002/jlac.199619960705There is no corresponding record for this reference.
- 34Lepore, S. D.; Khoram, A.; Bromfield, D. C.; Cohn, P.; Jairaj, V.; Silvestri, M. A. Studies on the Manganese-Mediated Isomerization of Alkynyl Carbonyls to Allenyl Carbonyls. J. Org. Chem. 2005, 70 (18), 7443– 7446, DOI: 10.1021/jo051040u34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXntVCgsr0%253D&md5=cc0d907b8c8285000866444254cd043bStudies on the manganese-mediated isomerization of alkynyl carbonyls to allenyl carbonylsLepore, Salvatore D.; Khoram, Anita; Bromfield, Deborah C.; Cohn, Pamela; Jairaj, Vinod; Silvestri, Maximilian A.Journal of Organic Chemistry (2005), 70 (18), 7443-7446CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)A study of the role of base in the isomerization of Mn-coordinated conjugated alkynyl carbonyls to the corresponding allenyl carbonyls is described. The use of phosphine additives indicates that Mn requires a ligand prior to isomerization with amine bases. Amine bases were also examd. for their efficacy in this isomerization reaction revealing a strong dependence on pKa. By contrast, K tert-butoxide led to rapid isomerization in the absence of added Mn ligand.
- 35Izzet, G.; Zeng, X.; Akdas, H.; Marrot, J.; Reinaud, O. Drastic Effects of the Second Coordination Sphere on Neutral vs. Anionic Guest Binding to a Biomimetic Cu(II) Center Embedded in a Calix[6]Aza-Cryptand. Chem. Commun. 2007, (8), 810– 812, DOI: 10.1039/B613564AThere is no corresponding record for this reference.
- 36Benoit, R. L.; Lefebvre, D.; Fréchette, M. Basicity of 1,8-Bis(Dimethylamino)Naphthalene and 1,4-Diazabicyclo[2.2.2]Octane in Water and Dimethylsulfoxide. Can. J. Chem. 1987, 65 (5), 996– 1001, DOI: 10.1139/v87-170There is no corresponding record for this reference.
- 37Beesley, R. M.; Ingold, C. K.; Thorpe, J. F. CXIX.─The Formation and Stability of Spiro-Compounds. Part I. Spiro-Compounds from Cyclohexane. J. Chem. Soc., Trans. 1915, 107 (0), 1080– 1106, DOI: 10.1039/CT915070108037https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaC2MXhvVGiuw%253D%253D&md5=de4306fddc79f71809a8556525abc983Formation and stability of spiro-compounds. I. Spiro-compounds from cyclohexanoBeesley, Richard M.; Ingold, Christopher K.; Thorpe, Jocelyn F.Journal of the Chemical Society, Transactions (1915), 107 (), 1080-1106CODEN: JCHTA3; ISSN:0368-1645.A series of investigations has been undertaken with the object of ascertaining "the effect produced by the alteration of the tetrahedral angle consequent on ring formation, on the formation and stability of a 2nd ring joined to the existing ring by a quaternary C atom common to both." The hypothesis was advanced that the angle formed by the 2 side chains attached to any 1 C atom of the cyclohexane ring will be altered in proportion to any change in angle between those valencies which participate in ring formation; i. e., the groups attached to 2 side chains emanating from the same C atom of a cyclohexane deriv., type (I), will be closer together than in a corresponding compd. having the open chain structure, type (II). Expts. show that this hypothesis is probably correct. For example a trans-spiro-acid, derived from a compd. of type (I) is more stable than trans-caronic acid, derived from a compd. of type (II). The above hypothesis and another untenable one are presented and discussed in some detail and diagrammatically represented by showing the effect of "strain" on the angles between the valencies (represented by the apices of an inscribed tetrahedron) of a (spherical) C atom. The bromination of CH2(CH2)4C(CH2CO2H)2 by means of PBr5 and Br led to the formation of a mixt. containing an acid product, probably C5H10>C(CHBrCO2H)(CH2CO2Et) (A), and a neutral product (B). The latter was shown to be a mixt. of cis-diethyl α,α'-dibromocyclohexane-1,1-diacetate (C) (not obtained in the pure state) and the trans-lactone (D), C5H10>C.CH(CO2Et).O.CO.CHBr, prisms from petroleum or alc., m. 96°, b20 225-30°. (D) was sepd. from the mixt. (B) by the addition of an equal vol. of petroleum (b. 60-70°) and was also synthesized by boiling (C) with C5H5N [whereby only the trans-form of (C) was converted into (D)] or by distg. (C), whereby both the cis- and trans-forms were converted. The isomeric cis-lactone (D'), microneedles, m. 69-70°, was formed in 25% yield upon distg. (C) from which (D) had been previously removed by means of C5H5N. α-Hydroxycyclohexane-1,1-diacetic acid lactone (E), C5H10>C.CH(CO2H).O.CO.CH2, b13 240-1°, crystg. after long standing and seeding, microneedles, m. 91-2° (silver salt, amorphous), was formed from (A) by the action of boiling Na2CO3. The free acid (F) corresponding to (E) could not be isolated and was found to be stable only in the form of its salts. The amorphous silver salt and cryst. sodium salt of (F) were prepd. The dianilide of (F), C5H10>C(CH2CONHPh)CH(OH)CONHPh, needles, m. 97°. The aniline salt of (E), silky needles, m. 104°. When (A) was added to boiling concd. KOH and the reaction mixt. cooled and acidified, trans-cyclohexane-spiro-cyclopropane-1,2-dicarboxylic acid (G), C5H10>C.CH(CO2H).CHCO2H, flattened needles, m. 237°, was formed. Its silver salt sepd. in the form of a cryst. powder: its dianilide, needles, m. 292°. The filtrate from (G) after extn. with Et2O and fractionation under reduced pressure yielded the cis-isomer (H) of (G), needles, m. 198°, more readily formed by distg. (G) which is first converted into the anhydride (J), C5H10>C.CH.CO.O.CO.CH, needles, m. 102°, which on treatment with alkali and subsequent acidification yields (H). (J) was also readily prepd. by the interaction of (H) and AcCl, whereas (G) is not acted upon by this reagent. The anilic acid, C5H10>C.CH(CO2H).CHCONHPh, derived from (J), small needles,m. 207° (decompn.); the corresponding anil, m. 119°. When heated in a sealed tube with 50% concd. HCl at 180° for 5 hrs., (H) is partially reconverted into (G). On attempting to replace the Br in (D) by an OH group, by means of moist Ag2O, ethyl α-hydroxycyclohexane-1,1-diacetate lactone, C5H10> C.CH2CO.O.CHCO2Et, b21 210°, was obtained and yielded (E) on hydrolysis. The following hydrolysis products were formed when (D) was treated with boiling 15% aq. NaOH:C5H10>C:CHCO2H (K), m. 92° (identical with Wallach's acid as shown by the formation of the dibromide, m. 135-6°; ref. not given), and the trans-lactonic acid of α,α'-dihydroxycyclohexane-1,1-diacetic acid (L), C5H10>C.CH(OH).CO.O.CHCO2H.H2O, prisms, 100°, anhydrous, m. 145°. (D') when subjected to a similar hydrolysis gave rise to a mixt. of (K), the cis-isomer (M) of (L), prisms, m. 168°, and cyclohexane-spiro-cyclopropanol-2,3-dicarboxylic acid (N), C5H10>C.C(OH)(CO2H).CHCO2H, pearly plates, m. 217°. Boiling alc. KOH, reacting with (D), yielded (K), (L) and (N). The action of 64% aq. KOH on (D) gave rise to a mixt. of (L), (N) and Δ1-cyclohexeneacetic acid, (O), CH2(CH2)3CH:C.CH2CO2H, m. 38° (identical with Wallach's compd.; also quant. formed by boiling (K) with 64% KOH, thus indicating that it was a byproduct in the above reaction). The Et ester of (O), b25 118-2° (cf. Auwers and Ellinger, C. A. 6, 1147). A similar reaction between 64% KOH and (D') gave rise to (O), (M) and (N). (K) and (N) were sepd. by treatment with dry Et2O in which (N) is insol. (L) was ordinarily sepd. from hydrolysis mixts. by esterifying and fractionating the ethyl ester, b25 206-10°. The following derivs. of (L) are described: disodium salt, cryst.; disilver salt, powder; aniline salt, microcrystals, m. 133-4°; dianilide, C5H10>C[CH(OH)CONHPh]2, short needles, m. 169°. (L) does not react with AcCl, is not reduced by AgOH, and when heated with H2O in a sealed tube or when distd., passes into (M). The isolation of (M) was effected by esterifying hydrolysis mixts. and collecting the fraction of highest b. p., which was subsequently hydrolyzed with HCl. (M) was readily acetylated. The following derivs. of (M) were prepd.: disilver salt; dianilide, needles, m. 169° (not identical with the dianilide derived from (L)); acetate, C5H10>CH(OAc).CO.O.CHCO2H, m. 156° (silver salt of the acetate, cryst. powder). The spiro-acid (N), which like (L) could not be acetylated, which is not converted into the lactone on heating and is otherwise stable, gave rise to the following compds.: silver salt, cryst. powder; anilide, needles, m. 202°. Concd. H2SO4 acting upon (L) at 95-100°, gave rise to small amts. of cyclohexane-spiro-cyclopentanone, oil (forming a semicarbazone, needles, m. 175°), and an unidentified compd., m. 105°. When heated with an equal amt. of H2O in a sealed tube at 240° for 0.5 hr., (L) yielded the lactonic acid of α-hydroxy-α'-cyclohexan-1-olsuccinic acid, C5H10>C.O.CO.CH(OH).CHCO2H, cubical prisms, m. 131°, whose disodium salt, disilver salt and aniline salt, m. 123°, were prepd.
- 38Sammes, P. G.; Weller, D. J. Steric Promotion of Ring Formation. Synthesis 1995, 1995 (10), 1205– 1222, DOI: 10.1055/s-1995-4099There is no corresponding record for this reference.
- 39Nagai, A.; Ochiai, B.; Endo, T. Cationic Ring-Opening Polymerization of Optically Active N-Substituted Cyclic Thiourethanes. Macromolecules 2004, 37 (20), 7538– 7542, DOI: 10.1021/ma049114b39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXntVOrtbg%253D&md5=a965555fa54b8dffd727951837da3c09Cationic ring-opening polymerization of optically active N-substituted cyclic thiourethanesNagai, Atsushi; Ochiai, Bungo; Endo, TakeshiMacromolecules (2004), 37 (20), 7538-7542CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)N-substituted cyclic thiourethanes, i.e., [4(S)-(methoxycarbonyl)-N-benzyl-1,3-oxazolidine-2-thione (BnSL), 4(S)-(methoxycarbonyl)-N-benzoyl-1,3-oxazolidine-2-thione (BzSL), and 4(S)-(methoxycarbonyl)-N-acetyl-1,3-oxazolidine-2-thione (AcSL)], were synthesized from L-serine Me ester hydrochloride and were polymd. using Me trifluoromethanesulfonate to obtain the corresponding well-defined polythiourethanes. The mol. wt. of the polymers can be controlled by the ratio of the monomers to the initiator and the mol. wt. distributions are narrow (Mw/Mn < 1.15), similar to the previously reported polymn. of a cyclic thiourethane [4(S)-(methoxycarbonyl)-1,3-oxazolidine-2-thione (SL)]. The polymn. rates are on the order of SL > BnSL > BzSL > AcSL, which agrees well with the nucleophilicity of the thiocarbonyl moieties of the monomers (SL, BnSL BzSL, and AcSL). The Cotton effects in the CD spectra of the polymers from the N-substituted monomers exhibit an almost inverse shape with that of poly(SL) and the sp. rotations' signs also inversed, suggesting the idea that poly(SL) and N-substituted polymers take different high order structures.
- 40Nagai, D.; Sato, M.; Ochiai, B.; Endo, T. Controlled Cationic Ring-Opening Polymerization of a Six-Membered Cyclic Thiourethane. Macromolecules 2004, 37 (10), 3523– 3525, DOI: 10.1021/ma049839f40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXivFKqu7g%253D&md5=4bb16826aed0b5334f6d3e6764e72128Controlled cationic ring-opening polymerization of a six-membered cyclic thiourethaneNagai, Daisuke; Sato, Masato; Ochiai, Bungo; Endo, TakeshiMacromolecules (2004), 37 (10), 3523-3525CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)A well-defined polythiourethane was obtained by controlled cationic ring-opening polymn. of 3-benzyl-1,3-oxazinane-2-thione. Control of mol. wt. was also achieved by using dithiocarbamate as a terminator. The polymer showed high refractive index and thermal stability. Exptl. details on 3-benzyl-1,3-oxazinane-2-thione monomer characterization are given in the supporting information.
- 41Awheda, I.; Saygili, N.; Garner, A. C.; Wallis, J. D. Activation and Regioselectivity of Five-Membered Cyclic Thionocarbamates to Nucleophilic Attack. RSC Adv. 2013, 3 (47), 24997– 25009, DOI: 10.1039/c3ra41074aThere is no corresponding record for this reference.
- 42Liu, Y.; Bejjanki, N. K.; Jiang, W.; Zhao, Y.; Wang, L.; Sun, X.; Tang, X.; Liu, H.; Wang, Y. Controlled Syntheses of Well-Defined Poly(Thionophosphoester)s That Undergo Peroxide-Triggered Degradation. Macromolecules 2019, 52 (11), 4306– 4316, DOI: 10.1021/acs.macromol.9b00061There is no corresponding record for this reference.
Supporting Information
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