Ion Pair-Directed Regiocontrol in Transition-Metal Catalysis: A Meta-Selective C-H Borylation of Aromatic Quaternary Ammonium Salts

The use of noncovalent interactions to direct-transition-metal catalysis is a potentially powerful yet relatively underexplored, strategy,, with most investigations thus far focusing on using hydrogen bonds as the controlling element. We have developed an ion pair directed approach to controlling regioselectivity in the iridium-catalyzed borylation of two classes of aromatic quaternary ammonium salts, leading to versatile meta-borylated products. By examining a range of substituted substrates, this provides complex, functionalized aromatic scaffolds amenable to rapid diversification and more broadly demonstrates the viability of ion-pairing for control of regiochemistry in transition-metal catalysis.