N-Spiro Chiral Quaternary Ammonium Bromide Catalyzed Diastereo- and Enantioselective Conjugate Addition of Nitroalkanes to Cyclic α,β-Unsaturated Ketones under Phase-Transfer Conditions

Abstract

[reaction, structure: see text] Conjugate addition of various prochiral nitroalkanes to cyclic alpha,beta-unsaturated ketones was found to be efficiently catalyzed by N-spiro C2-symmetric chiral quaternary ammonium bromide 1b possessing a 3,5-bis(3,4,5-trifluorophenyl)phenyl substituent under solid-liquid phase-transfer conditions to afford the corresponding gamma-nitro ketones in excellent chemical yields with unprecedented levels of diastereo- and enantiocontrol.