Highly enantioselective addition of linear alkyl alkynes to linear aldehydes

Abstract It is discovered that the use of biscyclohexylamine (Cy 2 NH) as an additive can greatly enhance the enantioselectivity for the reaction of linear alkyl alkynes with linear aldehydes. The combination of ( S )-BINOL (20 mol %), Cy 2 NH (5 mol %), ZnEt 2 (2 equiv), and Ti(O i Pr) 4 (0.5 equiv) catalyzes the reaction at room temperature in diethyl ether solution with 81–89% ee and 57–77% yield.