Controlled Ring‐Opening Polymerization of O‐Carboxyanhydrides Using a β‐Diiminate Zinc Catalyst. Issue 42 (6th October 2016)

• Record Type: Journal Article
• Authors: Wang, Ruibo; Zhang, Jiawei; Yin, Qian; Xu, Yunxiang; Cheng, Jianjun; Tong, Rong
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 42(2016)
• Page Start: 13010
• Page End: 13014
• Publication Date: 2016-10-06
• Subjects: copolymerization -- O-carboxyanhydrides -- ring-opening polymerization -- stereoregularity -- zinc; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201605508
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Recently O ‐carboxyanhydrides (OCAs) have emerged as a class of viable monomers which can undergo ring‐opening polymerization (ROP) to prepare poly(α‐hydroxyalkanoic acid) with functional groups that are typically difficult to achieve by ROP of lactones. Organocatalysts for the ROP of OCAs, such as dimethylaminopyridine (DMAP), may induce undesired epimerization of the α‐carbon atom in polyesters resulting in the loss of isotacticity. Herein, we report the use of (BDI‐IE)Zn(OCH(CH3 )COOCH3 ) ((BDI)Zn‐1, (BDI‐IE)=2‐((2, 6‐diethylphenyl)amino)‐4‐((2, 6‐diisopropylphenyl)imino)‐2‐pentene), for the controlled ROP of various OCAs without epimerization. Both homopolymers and block copolymers with controlled molecular weights, narrow molecular weight distributions, and isotactic backbones can be readily synthesized. (BDI)Zn‐1 also enables controlled copolymerization of OCAs and lactide, facilitating the synthesis of block copolymers potentially useful for various biomedical applications. Preliminary mechanistic studies suggest that the monomer/dimer equilibrium of the zinc catalyst influences the ROP of OCAs, with the monomeric (BDI)Zn‐1 possessing superior catalytic activity for the initiation of ROP in comparison to the dimeric (BDI)Zn complex. Abstract : A β‐diiminate zinc catalyst containing methyl lactate as initiator was used for the living polymerization of O ‐carboxyanhydrides (OCAs). A superior level of stereoretention for several enantiomerically pure OCA monomers was achieved.