1,2-Carbopentafluorophenylation of Alkynes: The Metallomimetic Pull-Push Reactivity of Tris(pentafluorophenyl)borane.

We report the novel single-step 1,2-dicarbofunctionalization of an arylacetylene with an allylsilane and tris(pentafluorophenyl)borane[B(C6F5)3], involving C-C bond formation with C-H bond scission at the β-position to the silicon atom of an allylsilane and B→C migration of a C6F5 group. The 1,2-carbopentafluorophenylation reaction occurs smoothly without the requirement for a catalyst or heating. Mechanistic studies suggest that the metallomimetic "pull-push" reactivity of B(C6F5)3 imparts consecutive electrophilic and nucleophilic characteristics to the benzylic carbon of the arylacetylene. Subsequent photochemical 6π-electrocyclization affords tetrafluoronaphthalenes, which are important in the pharmaceutical and materials sciences. Owing to the unique reactivity of B(C6F5)3 , the 1,2-carbopentafluorophenylation using 2-substituted furan proceeded with ring opening, and the reaction using silyl enolates formed C-C bond with C-O bond scission at the silyloxy-substituted carbon.