Electrophilic C(sp2)−H Borylation of Nonactivated and Deactivated Arenes with Pyramidal Boron Lewis Superacids

Abstract The electrophilic C–H borylation of unactivated and deactivated, electron-poor arenes is a challenging reaction even with the most electrophilic borenium-ion species. We now report the transition-metal-free borylation of a wide range of aromatics and polyaromatics with a pyramidal boron Lewis superacid from the 9-boratriptycene family. The mechanism of formation of a highly reactive pyramidal boron Lewis superacid and the origin of the slow and continuous release of this highly reactive borylation reagent in the presence of a Lewis base are reminiscent of the reactions of latent frustrated Lewis pairs with small molecules.