Diastereoselective and Enantioselective Henry (Nitroaldol)Reaction Utilizing a Guanidine-Thiourea Bifunctional Organocatalyst

摘要

A highly enantio-and diastereoselective Henry reaction of various aldehydes with nitroethane was developed using the guanidine-thiourea bifunctional catalyst 1 (syn selectivity of 86:14 to 99:1 with 84-99%ee).A variety of nitroalkanes was treated with unbranched and branched aldehydes and gave nitro alcohols with high syn diastereoselectivities (90:10 to99:1)and high enantioselectivities (85-95%ee).This reac-tion was successfully utilized in a straightforward synthesis of (4S,5R)-epi-cytoxazone.