Construction of sulfur-substituted methylenecyclobutanes via thioaromatization of [1.1.1]propellane with sulfenamides

Abstract

Herein, we report a metal-free catalytic strategy for the efficient synthesis of sulfur-substituted methylenecyclobutanes via the thioaromatization of [1.1.1]propellane. This transformation proceeds with high atom economy, broad functional group tolerance, and good scalability. The resulting methylenecyclobutanes possess multiple reactive sites, enabling diverse downstream derivatizations and thus underscoring their synthetic utility. Mechanistic studies supported by DFT calculations indicate that the reaction is initiated by the formation of a sulfur ylide intermediate, followed by a [2,3]-Wittig rearrangement, a subsequent Alder-type reaction involving thioxanthone (TXT), and a final deamination step that delivers the target product while regenerating the catalyst.