Synthesis of Allenyl Sulfur Compounds via Copper-Catalyzed Formal [3,3]-Rearrangement of O -Propargyl Carbamothioates

A base-free, copper-catalyzed formal [3,3]-rearrangement of O -propargyl carbamothioates has been developed, enabling the efficient synthesis of allenyl sulfur compounds in high yields with excellent regioselectivity. The method accommodates various O -propargyl carbamothioates, including those bearing primary, secondary, and tertiary alkyl substituents, and tolerates a broad range of functional groups. Mechanistic investigations suggest that the rearrangement proceeds via a pseudointramolecular nucleophilic attack of a sulfur anion on a copper–allenylidene intermediate.