Asymmetric synthesis of tertiary vinyl carbinols by highly stereoselective methylation of α-methyl-β-ketosulfoxides with aluminum reagents

Methylation of chiral acyclic α-methyl-β-ketosulfoxides with Me3Al and Me2AlCl is reported. Induced configuration at hydroxylic carbon is mainly controlled by the configuration of the sulfinyl group, with deʹs higher than 90% in most of the cases regardless the configuration at C-α. The stereochemical pathway seems to be different with both reagents, thus affording a higher stereoselectivity with Me2AlCl. Pyrolytic desulfinylation and hydrogenolysis of the C–S bond allowed the transformation of the resulting hydroxysulfoxides into interesting optically pure tertiary methyl carbinols.