Homochiral l-prolinamido-sulfonamides and their use as organocatalysts in aldol reactions

Abstract

The synthesis of new homochiral l-prolinamido-sulfonamides 1–7 from enantiomerically pure (R,R)-11,12-diamino-9,10-dihydro-9,10-ethanoanthracene (R,R)-8 is reported. The l-prolinamido-sulfonamides 1–7 were tested as organocatalysts (10mol%) in the aldol reaction of p-nitrobenzaldehyde and acetone in dichloromethane at room temperature in the presence of water (1equiv) and acetic acid (20mol%) giving good to high yields and enantioselectivities. Catalyst 4 (10mol%) afforded the best results in the aldol reaction of acetone with p-substituted-benzaldehydes with electron withdrawing groups (i.e., nitro, cyano, bromo and chloro, up to 97% yield and 90% ee). The origin of the enantioselective induction was modeled using DFT methods. The estimated enantioselectivity for the model system is consistent with the experimental data.