Copper-Catalyzed Ring-Opening Silylation of Benzofurans with Disilane.

The catalytic ring-opening silylation of benzofurans has been achieved by employing a copper catalyst and 1,2-di-tert-butoxy-1,1,2,2-tetramethyldisilane, which could be easily prepared and handled without special care. The reaction afforded (E)-o-(β-silylvinyl)phenols with complete stereoselectivity. The scope of benzofurans was well explored, and functional groups such as chloro, fluoro, and acetal were compatible with the reaction conditions. DFT calculations were used to determine the energy profile of the silylation and the origin of the stereoselectivity. The silylated product was proven to be useful as a synthetic intermediate and subsequently underwent transformations such as Pd-catalyzed cross-coupling with iodoarenes.