C(2)-Symmetric dialkoxyphosphoramide and dialkoxythiophosphoramide derivatives of (1R, 2R)-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 (1R, 2R)-1,2-diaminocyclohexane were prepared by the reactions of diethoxyphosphinic chloride, diethoxythiophosphinic chloride, and diisopropoxyphosphinic chloride with (1R, 2R)-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.
Shi
Min
M
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China. Mshi@pub.sioc.ac.cn
Wu
Xiao-Feng
XF
Rong
Guobin
G