Rh-Catalyzed Double Coupling Reaction of α-Fluoroalkyldiazo Iodonium Reagent with Internal Alkynes†

Abstract

Catalytic carbene-transfer reactions of diazo compounds with alkynes provide a reliable route to various strained-ring structures. In this context, the development of new metal carbynoid species has emerged as a powerful strategy to achieve unconventional reactivity. Herein, we report a Rh₂(esp)₂-catalyzed double coupling reaction of an α-fluoroalkyl diazo iodonium reagent with internal alkynes. This transformation offers straightforward access to tetrasubstituted difluoroalkyl cyclopropenes bearing a ketone moiety. Subsequent intramolecular cyclization efficiently affords difluoroalkyl 2-oxabicyclo[3.1.0]hex-3-enes in good yields with excellent diastereoselectivity. Mechanistic studies reveal that the α-difluoroalkyl diazo iodonium reagent functions as a carbynyl cation equivalent, with the alkyne serving as both a carbene acceptor and a nucleophile. Consequently, this one-pot four-component reaction is proposed to proceed via the following sequence: diazo decomposition to generate a metal carbynoid species, cyclopropenation, nucleophilic addition of the alkyne to the cyclopropenyl iodo intermediate, a second alkyne addition, and final hydration to deliver the ketone product.