AZIRIDINO ALCOHOLS AS CATALYSTS FOR THE ENANTIOSELECTIVE ADDITION OF DIETHYLZINC TO ALDEHYDES

The chiral aziridino alcohols 1 -3 have been prepared either from amin o acids (1a from serine; 1b - 1i and 3 from threonine; 2a - 2e from al lo-threonine) or via asymmetric synthesis (1j, 1k, 1l and 2f from meth yl cinnamate). These easily available ligands act as catalysts for the enantioselective addition of diethylzinc to benzaldehyde, with up to 90% stereoselectivity. The absolute configuration of the alcohol produ ct is dependent on the substitution pattern of the aziridine ring, and different transition state models are proposed to explain the observe d switch in enantioselectivity. The C-2-symmetric aziridino diols 4a - 4h have been prepared from tartaric acid, and also catalyze the organ ozinc addition reaction with high chemicals yields and up to 94% e.e. C-2-symmetric ligands 5a - 5c, with ether sidechains, were less effici ent (46% e.e. at best). The most efficient ligand (4c) was also tested in the addition to aldehydes 9 - 11, with 97% ee at best. (C) 1998 El sevier Science Ltd. All rights reserved.