Enantioselective Michael reactions of chiral secondary enaminoesters with 2-substituted nitroethylenes. Syntheses of trans,trans-2,4-disubstituted pyrrolidine-3-carboxylates

The Michael reaction of chiral 3-substituted secondary enaminoesters with 2 -substituted nitroethylenes leads to (Z)-adducts, with good to excellent di astereoselectivity. The nitro group of these adducts was catalytically redu ced to give, after cyclization and chiral amine elimination, pyrrolines or pyrrolidines after further reduction. In particular, the syntheses of ethyl (2R,3S,4S)-2,4-dimethylpyrrolidine-3-carboxylate and ethyl (2R,3R,4S) -2-( 4-methoxyphenyl)-4-(3,4-(methylenedioxy)phenyl)pyrrolidine-3-carboxylate ar e described.