Synthesis and application of dimeric Cinchona alkaloid phase-transfer catalysts: α,α′-bis[O(9)-allylcinchonidinium]-o, m, or p-xylene dibromide

Abstract

A dimeric Cinchona alkaloid ammonium salt, α,α′-bis[O(9)-allylcinchonidinium]-m-x ylene dibromide 4, has been developed as a new efficient phase-transfer catalyst; the catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using 4 provided 7 in a high enantiomeric excess (90–99% ee).