The versatile roles of ammonium salt catalysts in enantioselective reduction and alkylation of alpha,beta-unsaturated aldehydes: iminium catalysis, enamine catalysis and acid catalysis

A novel strategy for highly efficient utilization of chiral ammonium salt catalysts has been described in this paper. Three kinds of catalytic functions including iminium catalysis, enamine catalysis, and acid catalysis of chiral ammonium salt catalysts, have been achieved in the enantioselective reduction and alkylation reaction of alpha,beta-unsaturated aldehydes with alcohols.