Synthesis and stereoselective reductions of chiral β-iminosulfoxides

Abstract

Reaction of chiral non racemic β-ketosulfoxides with amines or condensation of the imine enolates with (−)-methyl sulfinate yield optically pure β-iminosulfoxides. The second method requires the presence of an excess of MgBr 2 in order to avoid epimerization at sulfur. The highly diastereoselective reduction of these substrates can be successfully achieved only with DIBAL/ZnBr 2 (d.e.97%). Hydrogenolysis of the CS bond on the obtained β-aminosulfoxides yields the protected with e.e. higher than 97%.