A new procedure for the synthesis of α-acyloxy aldehydes from ketones via α,β-epoxy sulfides

Abstract

α-Acyloxy aldehydes, as O-protected α-hydroxy aldehydes, have been prepared in good yields via a new procedure involving the sequence: (1) reaction of ketones with sulfur ylides to give α,β-epoxy sulfides, (2) ring opening with carboxylic acids, (3) oxidation of the α-acyloxy-β-hydroxy sulfide products by mCPBA to the corresponding sulfones; and (4) acyl migration followed by elimination of the sulfinate group. The last transformation was readily accomplished, in very good yields, by equivalent amounts of triethylamine in dichloromethane at room temperature (method A); or by acyl migration assisted by complexation of the liberated alkanthiol accomplished in the α-acyloxy-β-hydroxy sulfides by Ag2O in acetonitrile to give the same α-acyloxy aldehydes (method B). The presented procedure, compared to alternative procedures, has advantages including easily available key intermediates (α,β-epoxy sulfides), mildness of the reactions conditions, more general procedure (applied to different types of α-hydroxy aldehydes).