Stereoselective protonation and reduction of β-sulphinyl enamines. X-Ray molecular structure of N-benzyl-2-(p-tolylsulphinyl)propylamine

Abstract

Reduction of β-substituted β-sulphinyl enamines by acyloxyborohydrides in the presence of carboxylic acids leads to β-sulphinyl amines in good chemical yield and diastereoisomeric excess (de) up to 92%. Two methods of reduction, differing by the introduction sequence of the acid, are examined. The stereoselectivity is enhanced with large proton donors and strong acids but is less dependent on the type of reducing agent and solvent used. A mechanism for the stereoselective protonation is proposed.