Silylium Ion Initiated Intramolecular Friedel–Crafts-Type Cyclization of 1,1-Difluoroalkenes with Subsequent Hydrodefluorination of C(sp3)–F Bonds

Abstract

AbstractThe strong electrophilicity of silylium ions has been leveraged to probe an intramolecular Friedel–Crafts-type cyclization of aryl-tethered 1,1-difluoroalkenes. The reaction is presumed to be initiated by a preferential electrophilic silylation of the carbon–carbon double bond over the activation of one of the vinylic C(sp2)–F bonds. Subsequent cyclization followed by hydrodefluorination of the resulting C(sp3)–F bonds leads to the final product. The resulting tetraline derivatives were obtained in moderate to good yields. Distinct from earlier reports, the reaction proceeds with the perfluorinated tetraphenylborate counteranion under ambient conditions without the prerequisite of a carborate counteranion associated with the silylium ion intermediates.