Rhodium-catalyzed rearrangement of alpha-diazo thiol esters to thio-substituted ketenes. Application in the synthesis of cyclobutanones, cyclobutenones, and beta-lactams.

Exposure of alpha-diazo thiol esters (1) to the action of catalytic rhodium(II) acetate leads to a remarkably facile "thia-Wolff rearrangement", producing thio-substituted ketenes which combine with a variety of ketenophiles to provide access to alpha-thiocyclobutanones, cyclobutenones, and beta-lactams. Reductive desulfurization of these cycloadducts takes place under mild conditions and in excellent yield, and this sequence thus represents a useful new alternative to the existing dichloroketene-based methodology for the synthesis of four-membered carbocycles and heterocycles.