Selective Coupling of β-(Borylvinyl)silanes by a Gold-Catalyzed Hiyama Reaction-An Easy Way to Diaryl-Substituted Vinyl Boronates.

The use of diaryl-substituted vinyl boronates, a class of chemical building blocks with well-known synthetic utility, is principally limited by the difficulty faced in their preparation. Herein, we present a convenient synthetic strategy based on a gold-catalyzed Hiyama arylation of (Z)-β-(borylvinyl)silanes, which are easily accessible by hydroboration of silylalkynes. By exploiting the highly electronegative nature of the gold(III) intermediate (which is accessed by light-assisted oxidation using aryl diazonium salts), a selective activation of the silyl group in the presence of the boron moiety is achieved. This opens a route to selectively synthesize diaryl-substituted vinyl boronates. The reaction shows a broad substrate range, excellent functional group tolerance, and perfect chemoselectivity. Experimental studies and density functional theory (DFT) calculations allowed us to elucidate the mechanism of the reaction. The synthetic potential was demonstrated by downstream transformations providing a facile route to bifunctional phenanthrenes and triaryl-substituted olefins.