C_2-Symmetric diphenylphosphoramide and diphenylthiophosphoramide derived from (1R,2R)-1,2-diaminocyclohexane as ligands for the titanium(IV) alkoxidepromoted addition of diethylzinc to aldehydes

摘要

Chiral C_2-symmetric diphenylphosphoramide 4 and diphenylthiophosphoramide 5 were prepared from the reaction of diphenylphosphinic chloride and diphenylthiophosphinic chloride with (1R,2R)-(-)-1,2-diaminocyclohexane in the presence of diisopropylethylamine in high yields. They were used as chiral ligand in the catalytic asymmetric addition reaction of diethylzinc to aldehydes 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.