Bifunctional Organocatalysts in the Asymmetric Michael Additions of Carbonylic Compounds to Nitroalkenes

In the past decade, the organocatalytic asymmetric Michael addition has emerged as one of the most important carbon-carbon bond forming reactions in organic chemistry. As an example, the conjugated addition of ketones to nitroolefins has received extensive attention, since the resulting nitroalkanes are versatile intermediates in which the nitro group can be transformed into various useful functional groups. Furthermore, the reaction has the ability to introduce two vicinal stereogenic centers in a single step. Stimulated by the seminal work of List, Barbas and coworkers, several research groups have focused on the development of novel bifunctional organocatalysts bearing amine and hydrogen donor functionalities. This review will focus on the development of multifunctional chiral organocatalysts derived from proline, pyrrolidine, cinchona alkaloids, thioureas and sulfonamides in the asymmetric Michael addition to nitroalkenes.