C 2 ‐Symmetric dialkoxyphosphoramide and dialkoxythiophosphoramide derivatives of (1 R , 2 R )‐1,2‐diaminocyclohexane as chiral ligands for the titanium(IV) alkoxide‐promoted asymmetric addition reactions of diethylzinc to arylaldehydes

C 2 ‐Symmetric chiral diethoxyphosphoramide 4 , diethoxythiophosphoramide 5 , and diisopropoxyphosphoramide 6 of (1 R , 2 R )‐1,2‐diaminocyclohexane were prepared by the reactions of diethoxyphosphinic chloride, diethoxythiophosphinic chloride, and diisopropoxyphosphinic chloride with (1 R , 2 R )‐1,2‐diaminocyclohexane, respectively. They were used as catalytic chiral ligands in the asymmetric addition reactions of diethylzinc to aldehydes in the presence of titanium(IV) isopropoxide to give the corresponding sec ‐alcohols with 43–70% ee. Chiral ligands 4 and 5 gave the sec ‐alcohols with opposite absolute configuration. Chirality 14:90–95, 2002. © 2002 Wiley‐Liss, Inc.