Palladium-catalyzed Arylation of (Z)-Germyl(stannyl)ethenes

摘要

The (Z)-germyl(stannyl)ethenes 1 can be stereospecifically prepared by the reaction of an acetylene with a germyltin under mild conditions. Product yields are sutisfactory. Because the ethenes 1 have a vinyltin unit, they may undergo an arylation reaction extending the conjugation of carbon to carbon bonds, although a successful arylation of 1a has not yet been reported. The phenylation of a silicon analogue, a (Z)-silyl(stannyl)ethene, with bromobenzene in the presence of BnPdCl(PPh3)2, is the only reported example of the destannylative arylation of a vinyltin with a silyl group β to tin with cis-disposition. However, our attempted application of that catalyst to the cross-coupling of 1a with bromobenzene at 70 °C failed. More recently, a specific catalyst combination has been described for the arylation of (Z)-silyl(stannyl)ethenes with aryl halides (X = Br, I). We present first report of the reaction of 1 with aryl halides (bromide or iodide) by means of a catalyst combination (Scheme 1).