ORGANOBORANES FOR SYNTHESIS .18. C-2-SYMMETRICAL ALPHA,ALPHA'-DISUBSTITUTED-2,6-PYRIDINEDIMETHANOLS AS CATALYTIC CHIRAL LIGANDS FOR THE ENANTIOSELECTIVE NUCLEOPHILIC-ADDITION OF DIETHYLZINC TO ALDEHYDES

Several new chiral auxiliaries with differing steric and electronic en vironments, such as alpha,alpha'-dimethyl-2,6-pyridinedimethanol, a,al pha'-ditrifluoromethyl-2,6-pyridinedimethanol, a,alpha'-dipentafluoroe thyl-2,6-pyridinedimethanol and alpha,alpha'-diallyl-2,6-pyridinedimet hanol, have been examined and compared with alpha,alpha'-di-t-butyl-2, 6-pyridinedimethanol for their ability to control the enantioselective addition of diethylzinc to benzaldehyde. The best chiral ligand has b een tested for other representative aldehydes with varying steric and electronic requirements. The product alcohols are obtained in 21-78% e e. (C) 1997 Wiley-Liss, Inc.