Catalysts' evolution in the asymmetric conjugate addition of nitroalkanes to electron-poor alkenes

The conjugate addition of nitroalkanes to electron-poor alkenes is a widely used process which only in the late nineties of the last century has efficiently evolved in its asymmetric version. Synthetic protocols based on chiral organocatalytic methods have been largely exploited for the generation of optically pure gamma-nitro derivatives through carbon-carbon bond formation. Chiral metal-ligand complexes have also been successfully employed for these conjugate additions, although their use in the synthesis of targeted bioactive compounds still appears rather limited. Most of the practical applications of the obtained adducts are based on the easy conversion of the nitro group into a primary amine directed to the preparation of nitrogen-containing structures. This review aims to provide a journey of the catalyst usage for the enantioselective conjugate addition of nitroalkanes to electron-poor olefins, from the early attempts to the latest achievements. The discussion is categorized according to the nature of different catalytic systems, and a final section reporting selected applications to targeted compounds is provided.