Asymmetric Propargylic Substitution

Significance

While catalytic asymmetric allylic substitution of allylic alcohols and their derivatives has been widely studied, the propargylic variant has not yet been developed. This report describes the use of a tetranuclear ruthenium complex ({Cp*RuCl}₄) mixed with a disulfide ligand (1) to obtain moderate enantioselectivities and reasonable yields. Many ligands with various substitution patterns on the central phenyl ring were screened, with 1 giving the best results. Various electronic substitutions on the aryl group in the substrate were tolerated (o-MeOC₆H₄ gave 61% yield, 72% ee and p-ClC₆H₄ gave 57% yield, 68% ee, while bulky substrates, e.g. 1- and 2-naphthyl,
p-PhC₆H₄, and 3,5-Ph₂C₆H₃ gave 70%ee).