Copper-Catalyzed Borylation and Silylation of Dichlorocyclobutenones.

We report copper-catalyzed borylation and silylation of dichlorocyclobutenones, which furnish the boron-substituted and siliconsubstituted polyfunctionalized cyclobutenones in high yields. The reactions proceed under mild reaction conditions, show broad substrate scope, and display high chemoselectivity. In addition, a series of transformations of the corresponding products has been realized.