Remote stereocontrol by sulfinyl groups: hydrocyanation of δ-ketosulfoxides

Reactions of (2-p-tolylsulfinyl)benzyl alkyl (and aryl) ketones (δ-ketosulfoxides) with Et2AlCN in the presence of Yb(OTf)3 take place in a completely stereoselective manner, demonstrating the efficiency of the sulfinyl group in the control of the stereoselectivity of 1,5-asymmetric hydrocyanation processes as well as the ability of Yb(OTf)3 to form chelated species with ketosulfoxides. The behavior of their methyl derivatives at the benzylic position is dependent on the configuration at the chiral carbon. The resulting sulfinyl cyanohydrins were readily transformed into α-hydroxyamides by hydrolysis of the CN group and hydrogenolysis of the C–S bond.