A squaramide and tertiary amine: an excellent hydrogen-bonding pair organocatalyst for living polymerization

Liu, Jingjing; Chen, Cheng; Li, Zhenjiang; Wu, Wenzhuo; Xu, Zhi; Zhang, Qiguo; Wu, Hao; Wang, Xin; Cui, Saide; Guo, Kai

doi:10.1039/c5py00508f

Cited by 45 publications

(25 citation statements)

References 35 publications

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“…Since the first report using 4‐dimethylaminopyridine for the ROP of lactide by Hedrick and coworkers, organocatalysis has drawn great attention in the area of ROP of lactones. Among the organocatalysts based on hydrogen‐bonding motifs, triazabicyclodecene (TBD), recognized as a “magic” catalyst, is one of the most active ones used for the ROP of lactones and has proposed a bifunctional mechanism for the ROPs that activates both the monomer and alcohol initiator through hydrogen bonding . However, the strong basicity and nucleophilicity of TBD lead to the competitive transesterifications.…”

Section: Introductionmentioning

confidence: 99%

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Zheng

Yuan

et al. 2018

J. Polym. Sci. Part A: Polym. Chem.

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Development of effective organocatalysts for the living ring‐opening polymerization (ROP) of lactones is highly desired for the preparation of biocompatible and biodegradable polyesters with controlled microstructures and physical properties. Herein, a new class of hydrogen‐bond donating bisurea catalysts is reported for the ROP of lactones under solvent‐free conditions. ROP of lactones mediated by the bisurea/7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (MTBD) catalyst exhibits a living/controlled manner, affording the polymers and copolymers with the well‐defined structure, predictable molecular weight, narrow molecular weight distribution, and high selectivity for monomer at low catalyst loadings at ambient temperature. The possible mechanism of bisurea/MTBD‐catalyzed ROP of lactones is proposed, in which the bisurea activates the carbonyl group of lactones while MTBD facilitates the nucleophilic attack of the initiating/propagating alcohol by hydrogen bonding. Moreover, the poly(ε‐caprolactone‐co‐δ‐valerolactone) [P(CL‐co‐VL)] random copolymers with various compositions were synthesized using the bisurea/MTBD catalyst. The measurements of thermal properties and crystalline structure demonstrate that the CL and VL units are cocrystallized in the crystalline phase of P(CL‐co‐VL) copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 90–100

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Section: Introductionmentioning

confidence: 99%

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Zheng

Yuan

et al. 2018

J. Polym. Sci. Part A: Polym. Chem.

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“…Therefore, squaramides may be suitable HB ROP catalysts for lactide polymerization, and their potential in this area remains unexplored. To date, the squaramide‐mediated ROP of lactide was reported on one occasion using a squaramide/(−)‐sparteine two‐component catalytic mixture . While the present study was in progress, a Pt‐functionalized aminosquaramide was also reported to oligomerize lactide …”

Section: Introductionmentioning

confidence: 66%

Bifunctional Squaramides as Organocatalysts for Lactide Polymerization: Catalytic Performance and Comparison with Monofunctional Analogues

et al. 2017

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Amine‐functionalized squaramides 1 and 2 were prepared and shown to be suitable polymerization organocatalysts for the controlled ring‐opening polymerization (ROP) of l‐lactide (l‐LA) in the presence of an alcohol source such as BnOH (which acts as an initiator) to afford chain‐length‐controlled and narrow‐dispersion poly(l‐lactide) (PLLA) under mild reaction conditions. The ROP experimental and polymer analysis data are consistent with the action of 1 and 2 as bifunctional hydrogen‐bonding (HB) catalysts that are able to activate both the lactide monomer and initiator BnOH thanks to their dual HB acceptor and donor properties. As a comparison, aminosquaramide 3, a direct analogue of 1 but a weaker HB donor because of the absence of electron‐withdrawing NH substituents, displays little lactide ROP activity, which highlights the key role of monomer activation through HB in the present systems. Unlike aminosquaramides 1 and 2, related monofunctional squaramides 4 and 5 are inactive in l‐LA ROP in the presence of BnOH, but the addition of NEt3, as an external HB acceptor, allows the ROP to proceed with the production of well‐defined PLLA. A cooperative dual activation with an activated monomer/activated chain‐end mechanism is most likely operative in the lactide ROP mediated by 1 and 2 in the presence of BnOH.

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“…Various H‐bond donor moieties with one, two or three binding sites have been used . b The most common are thioureas, perfluorinated alcohols, phenols, squaramides, sulfonamides, amido–indoles . Combination with organic bases (typically amines or diamines) as H‐bond acceptors afford binary systems.…”

Section: Ring–opening Polymerization Of ε–Caprolactone With (Bis)pyrimentioning

confidence: 99%

“…Various H-bond donor moieties with one, two or three binding sites have been used. 1b The most common are thioureas, 2 perfluorinated alcohols, 3 phenols, 4 squaramides, 5 sulfonamides, 6 amido-indoles.…”

mentioning

confidence: 99%

Ring-opening polymerization of ε-caprolactone catalyzed by ionic hydrogen bond activation with bis-pyridiniums

Gontard

Amgoune

Bourissou

2016

J. Polym. Sci. Part A: Polym. Chem.

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A squaramide and tertiary amine: an excellent hydrogen-bonding pair organocatalyst for living polymerization

Abstract: A hydrogen-bond motif based on a squaramide and sparteine efficiently promoted the ring-opening polymerization of l-lactide at ambient temperature.

Cited by 45 publications

References 35 publications

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Bifunctional Squaramides as Organocatalysts for Lactide Polymerization: Catalytic Performance and Comparison with Monofunctional Analogues

Ring-opening polymerization of ε-caprolactone catalyzed by ionic hydrogen bond activation with bis-pyridiniums

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