Nickel-Catalyzed Ipso-Borylation of Silyloxyarenes via C–O Bond Activation

A mild method to convert silyloxyarenes to pinacol boronic esters using nickel catalysis is described. In contrast to other borylation protocols of relatively inert C–O bonds, the method is competent in activating the carbon-oxygen bond of silyloxyarenes in isolated aromatic systems lacking a directing group. The catalytic functionalization of benzyl silyl ethers was also achieved under these conditions. Orthogonal reactivity of silyloxyarenes vs other electrophiles was demonstrated in the case of several cross-coupling reactions wherein the unaffected silyloxarene could be functionalized subsequently.