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



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 to 99:1) and high enantioselectivities (85–95 % ee). This reaction was successfully utilized in a straightforward synthesis of (4S,5R)-epi-cytoxazone.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)