Routes to building blocks for heterocyclic synthesis by reduction of ketene dithioacetals

Two general methods have been developed permitting the effective reduction of ketene dithioacetals to give substituted dithianes. Reduction with magnesium in methanol is less reliable than reduction with zinc in acetic acid. The greater inconsistency of magnesium in methanol has been investigated by a cyclic voltammetric study of the substrates. The utility of the dithianes has been successfully illustrated by cyclisations to afford, after deprotection, a variety of heterocyclic aldehydes. (C) 1997 Elsevier Science Ltd.