Anti-selective Mannich reactions of N-Boc and N-Cbz protected imines with unmodified aldehydes proceeded smoothly under the catalysis of a secondary amine–thiourea catalyst, which led to high yields (70%–95%) and excellent enantioselectivity (up to 96 ∶ 4 dr and >99% ee) under conventional organic synthetic operations.
A Designer Axially Chiral Amino Sulfonamide as an Efficient Organocatalyst for Direct Asymmetric Mannich Reactions of N-Boc-Protected Imines
作者:Taichi Kano、Yukako Yamaguchi、Keiji Maruoka
DOI:10.1002/anie.200805628
日期:2009.2.23
The moderate nucleophilicity of the axiallychiralaminosulfonamide (S)‐1 suppresses the problematic side reactions, including aldol reactions, in the asymmetricMannichreaction of N‐Boc‐protected imines with aldehydes. The corresponding adducts are obtained in good yield and excellent stereoselectivity (see scheme; Boc=tert‐butoxycarbonyl, Tf=trifluoromethanesulfonyl).