ASYMMETRIC MICHAEL ADDITION OF NITROALKANES TO PROCHIRAL ACCEPTORS CATALYZED BY PROLINE RUBIDIUM SALTS

Proline rubidium salts catalyze the asymmetric Michael addition of nit roalkanes to prochiral accepters. When(2S)-L-prolines were used, acycl ic Q-enones gave (S)-adducts and cyclic (Z)-enones gave (R)-adducts pr edominantly. Enantiomeric excesses exceeding 80% were attained in some reactions of secondary nitroalkanes. Primary nitroalkanes gave mixtur es of diastereomers which possess the same configuration at the beta-c arbon atom. The nitro group of the adducts can be replaced with hydrog en by Bu3SnH reduction. The overall transformation is equivalent to an asymmetric beta-alkylation of the enone. Functionalized nitroalkanes such as nitro alcohol, nitro ester, and nitroalkene may also be utiliz ed in the reaction. (C) 1997 Elsevier Science Ltd.