Cu−Catalyzed Enantioselective Conjugate Addition of Alkylzincs to Cyclic Nitroalkenes: Catalytic Asymmetric Synthesis of Cyclic α-Substituted Ketones
journal contributionposted on 19.06.2002, 00:00 by Courtney A. Luchaco-Cullis, Amir H. Hoveyda
An efficient and highly enantioselective (≥92% ee) catalytic method for conjugate addition of alkylzinc reagents to cyclic nitroalkenes is reported. Reactions are promoted in the presence of 0.5−5 mol % (CuOTf)2·C6H6 and 1−10 mol % of chiral amino acid-based phosphine ligands at 0 °C in toluene. The Cu-catalyzed reactions can be effectively carried out with small-, medium-, and large-ring nitroalkenes. Depending on the reaction conditions used, either the nitro or the corresponding α-substituted ketone product can be readily accessed by the present protocol.