Remote stereocontrol mediated by a sulfinyl group: synthesis of allylic alcohols via chemoselective and diastereoselective reduction of gamma-methylene delta-ketosulfoxides.

The efficiency of the sulfinyl group as a remote controller of the chemoselectivity and diastereoselectivity of the reduction of alpha, beta-unsaturated alpha-[2-(p-tolylsulfinyl)phenyl] substituted ketones 1 has been demonstrated in reactions carried out under NaBH4 in the presence of Yb(OTf)3 as the chelating agent. The starting unsaturated ketones have been prepared from the corresponding 2-(p-tolylsulfinyl) benzyl alkyl (and aryl) ketones 2 by insertion of the methylidene group under modified Mannich conditions, exploiting ultrasound irradiation to obtain the aminomethylation adducts and silica gel treatment to produce its complete elimination. Desulfinylation of the reduction products yielded the corresponding vinyl carbinols with high enantiomeric purity.