Counter-rotatable dual cinchona quinuclidinium salts and their phase transfer catalysis in enantioselective alkylation of glycine imines

Abstract

Dual cinchona quinuclidinium salts with a diphenyl ether linker were synthesized and used as powerful asymmetric phase transfer catalysts in the α-alkylation of imines of glycine and alanine ester with 0.01–0.1 mol% loading (17 examples, 92–99% ee). Skewed conformers of dual quinuclidiniums at TS were proposed to rationalize their high efficiency via DFT calculations.