Bis-CF3-bipyridine Ligands for the Iridium-Catalyzed Borylation of N-Methylamides

Abstract

Bipyridine and phenanthroline are well-established neutral ligands for promoting iridium-catalyzed borylations of aromatic C–H bonds. However, their use with aliphatic substrates is almost uncharted. Herein we demonstrate that introducing CF substituents at the 5- and 5′-positions of bipyridine generates ligands that enable an efficient and regioselective iridium-catalyzed borylation of the methyl group in a broad variety of methylamides. The reaction shows broad functional group tolerance and exhibits remarkable selectivity, offering a powerful approach for the borylation of challenging aliphatic C–H bonds. Mechanistic investigations, including computational analysis, suggest that the accelerating effect of the ligand is likely associated with the formation of non-covalent dispersion interactions between the carbonyl amide of the substrates and the trifluoromethylated pyridine rings of the ligand.