Highly enantioselective conjugate addition of 1-bromonitroalkanes to α,β-unsaturated ketones catalyzed by 9-amino-9-deoxyepiquinine

Asymmetric conjugate addition of 1-bromonitroalkanes to α,β-unsaturated ketones was studied using chiral primary amines as the catalysts. 9-Amino-9-deoxyepiquinine was found to be highly efficient catalyst for the transformation. 4-Bromo-4-nitroketones were obtained with excellent enantioselectivities (97–99% ee) and good yields (61–99%) for a variety of alkyl vinyl ketones. The product could be further debrominated with Bu3SnH/AIBN to provide chiral 4-nitroketones in good yield and without loss of the optical purity.