Highly stereoselective catalytic conjugate addition of acyl anion equivalent to nitroolefins

Abstract

Highly enantioselective conjugate addition of 2-unsubstituted azlactone 3 to various nitroolefins 4 was accomplished by the selective utilization of supramolecularly assembled, chiral tetraaminophosphonium aryloxide–arylhydroxide 1a·[2a]₂ as a requisite catalyst. The key to this achievement is the polarity dependence of the molecular associations of type 1·[2]_n and the crucial role of the proximal arylhydroxide 2 as a proton donor. The present method offers an attractive route to various optically active amino carbonyl compounds including β²-amino acids.