Enantioselective Conjugate Addition of nitromethane

The enantioselective conjugate addition of nitromethane to electron-poor alkenes is a powerful synthetic strategy allowing the introduction of a single carbon linked to a nitrogen atom in its higher oxidation state. The installation of a newly generated stereocenter in enantioenriched form and the subsequent reduction of the nitro group into an amino functionality represent a flexible gateway to the preparation of optically active amino-containing compounds. Organocatalytic methods are the the most exploited procedures for this purpose and may involve activation of the carbonyl group in the corresoponding enones and enals by optically active secondary amines (iminium ion catalysis). Activation of nitromethane using thiourea derivatives is also a viable approach to attain the corresponding adducts with high enantioselectivity. Chiral organometallic complexes of lanthanum, aluminium and copper are also successfully used for this purpose and are substantially based on the activation of both nitromethane and the Michael acceptor.