Palladium-Catalyzed Markovnikov Terminal Arylalkynes Hydrostannation: Application to the Synthesis of 1,1-Diarylethylenes

The palladium-catalyzed hydrostannation of terminal arylalkynes was achieved. The regioselectivity of the H-Sn bond addition across the triple bond was found to be controlled by an ortho substituent on the aromatic ring, whatever its electronic nature, to give exclusively alpha-branched vinylstannanes 2 in accordance with Markovnikov's rule. Subsequent Stille cross-coupling reaction of 2 with a variety of aryl halides readily provided, in moderate to good yields, a family of functionalized 1,1-diarylethylenes 1.