Iridium‐Catalysed C−H Borylation of Fluoroarenes: Insights into the Balance between Steric and Electronic Control of Regioselectivity

Abstract The iridium catalysed C−H borylation of polyfluorinated arenes and heteroarenes occurs rapidly and efficiently. As with other borylation reactions, whilst steric parameters dominate, an underlying electronic influence on reaction selectivity can be observed. Notably borylation regioselectivity in fluorinated (hetero)arenes is determined by purely electronic effects except for ortho ‐borylation between two fluorine atoms where steric effects of fluorine substituents become apparent. Borylation at the para position with respect to fluorine is disfavoured whereas a strong electronic preference for borylation para to the azinyl nitrogen of pyridine is observed. When these features co‐operate high selectivity can be expected. For these reactions, computations based on transition state, rather than intermediate, energies in iridium geometries showed excellent agreement between predicted and observed selectivities.