Highly enantioselective addition of linear alkyl alkynes to linear aldehydes

It is discovered that the use of biscyclohexylamine (Cy2NH) 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 %), Cy2NH (5 mol %), ZnEt2 (2 equiv), and Ti(OiPr)4 (0.5 equiv) catalyzes the reaction at room temperature in diethyl ether solution with 81–89% ee and 57–77% yield.