From meso-Lactide to Isotactic Polylactide: Epimerization by B/N Lewis Pairs and Kinetic Resolution by Organic Catalysts

B/N Lewis pairs have been discovered to catalyze rapid epimerization of meso-lactide (LA) or LA diastereomers quantitatively into rac-LA. The obtained rac-LA is kinetically polymerized into poly­(l-lactide) and optically resolved d-LA, with a high stereoselectivity k L/k D of 53 and an ee of 91% at...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2015-10, Vol.137 (39), p.12506-12509
Main Authors: Zhu, Jian-Bo, Chen, Eugene Y.-X
Format: Article
Language:English
Subjects:
Catalysis
Dioxanes - chemistry
Kinetics
Lewis Acids - chemistry
Magnetic Resonance Spectroscopy
Molecular Structure
Polyesters - chemistry
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Summary:B/N Lewis pairs have been discovered to catalyze rapid epimerization of meso-lactide (LA) or LA diastereomers quantitatively into rac-LA. The obtained rac-LA is kinetically polymerized into poly­(l-lactide) and optically resolved d-LA, with a high stereoselectivity k L/k D of 53 and an ee of 91% at 50.6% monomer conversion, by newly designed bifunctional chiral catalyst 4 that incorporates three key elements (β-isocupreidine core, thiourea functionality, and chiral BINAM) into a single organic molecule. The epimerization and enantioselective polymerization can be coupled into a one-pot process for transforming meso-LA directly into poly­(l-lactide) and d-LA.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.5b08658