Enantioselective Michael addition of α,α-disubstituted aldehydes to nitroolefins catalyzed by a pyrrolidine-pyrazole

An efficient protocol for the asymmetric catalytic Michael additions of alpha,alpha-disubstituted aldehydes to nitroolefins with a pyrrolidine-pyrazole is described. The desired products gamma-nitrocarbonyl compounds possessing an all-carbon quaternary center, were obtained in good yields and with high levels of enantioselectivities under solvent-free reaction conditions, employing benzoic acid as an additive. (C) 2014 Elsevier Ltd. All rights reserved.