1,1′-Binaphthyl ligands with bulky 3,3′-tertiaryalkyl substituents for the asymmetric alkyne addition to aromatic aldehydes

The BINOL ligand (R)-2 that contains bulky 3,3′-tertiaryalkyl groups shows improved catalytic properties over the previously reported 3,3′-substituted BINOL ligands in the asymmetric alkyne addition to aromatic aldehydes. It catalyzes the phenylacetylene addition to aromatic aldehydes with high enantioselectivity (86–94% ee) and good yields without using Ti(OiPr)4 and a Lewis base additive. The catalytic properties of several analogs of (R)-2 in the asymmetric alkyne addition to aldehydes have also been studied.