title: From meso-Lactide to Isotactic Polylactide: Epimerization by B/N Lewis Pairs and Kinetic Resolution by Organic Catalysts.
abstract: 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.
authors.affiliation: Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States.
authors.forename: Jian-Bo
authors.initials: JB
authors.lastname: Zhu
authors.affiliation: Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States.
authors.forename: Eugene Y-X
authors.initials: EY
authors.lastname: Chen
mesh_terms: D002384:Catalysis; D004146:Dioxanes / Q000737:chemistry*; D007700:Kinetics; D058116:Lewis Acids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011091:Polyesters / Q000737:chemistry*
chemical_list: D004146:Dioxanes; D058116:Lewis Acids; D011091:Polyesters; C033616:poly(lactide); C091880:dilactide