Rhodium-catalyzed rearrangement of alpha-diazo thiol eaters to thio-substituted ketenes. Application in the synthesis of cyclobutenones, 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", produ cing thio-substituted ketenes which combine with a variety of ketenophiles to provide access to alpha-thiocyclobutanones, cyclobutenones, and beta-lac tams. Reductive desulfurization of these cycloadducts takes place under mil d conditions and in excellent yield, and this sequence thus represents a us eful new alternative to the existing dichloroketene-based methodology for t he synthesis of four-membered carbocycles and heterocycles.