Double stereoselection in the aldol-type synthesis of gamma-methyl and gamma- alkoxy-beta-hydroxyketones mediated by alpha-sulphinylhydrazones

Optically active γ-methyl-β-hydroxy and γ-alkoxy-β-hydroxy ketones have been obtained by condensing chiral racemic aldehydes with chiral α-sulphinyl hydrazones. Good to excellent enantioselectivity and diastereoselectivity, both strongly dependent on the nature of the substrates and the reaction conditions, were achieved. The absolute and relative configuration of some of the ketols have been established, and a model to account for the stereochemical outcome of this reaction is discussed.