期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 54, 期 49, 页码 14858-14861出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201503111
关键词
aluminum complexes; chiral salan ligands; poly(lactic acid); polymerization; stereoselective catalysis
资金
- Israel Science Foundation
- U.S.-Israel Binational Science Foundation
Alkyl aluminum complexes of chiral salan ligands assembled around the 2,2'-bipyrrolidine core form as single diastereomers that have identical configurations of the N donors. Active catalysts for the polymerization of lactide were formed upon the addition of benzyl alcohol. Polymeryl exchange between enantiomorphous aluminum species had a dramatic effect on the tacticity of the poly(lactic acid) (PLA) in the polymerization of racemic lactide (rac-LA): The enantiomerically pure catalyst of the nonsubstituted salan ligand led to isotactic PLA, and the racemic catalyst exhibited lower stereocontrol. The enantiomerically pure catalyst of the chloro-substituted salan ligand led to PLA with a slight tendency toward heterotacticity, whereas the racemic catalyst led to PLA of almost perfect heterotacticity following an insertion/auto-inhibition/exchange mechanism.
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