C-2-Symmetric diphenylphosphoramide and diphenylthiophosphoramide derived from (1R,2R)-1,2-diaminocyclohexane as ligands for the titanium(IV) alkoxide-promoted addition of diethylzinc to aldehydes

Chiral C-2-symmetric diphenylphosphoramide 4 and diphenylthiophosphoramide 5 were prepared from the reaction of diphenylphosphinic chloride and diphen ylthiophosphinic chloride with (1R,2R)-(-)-1,2-diaminocyclohexane in the pr esence of diisopropylethylamine in high yields. They were used as chiral li gands in the catalytic asymmetric addition reaction of diethylzinc to aldeh ydes in the presence of titanium(IV) isopropoxide to give the corresponding sec-alcohols in 70-83% ee with an (R)-configuration and in 40-50% ee with an (S)-configuration, respectively. (C) 1999 Elsevier Science Ltd. All righ ts reserved.