Transition metal-catalysed direct borylation of hydrocarbons via C–H bond activation has received a remarkable level of attention as a popular reaction in the synthesis of organoboron compounds owing to their synthetic versatility.

Here we describe the discovery of a new class of C–H borylation catalysts and their use for regioselective C–H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir–C­(thienyl) or Ir–C­(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C–H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C­(sp3)–H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C–H bonds. A number of late-stage C–H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C­(sp2)–H and C­(sp3)–H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir­(bis)­boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C–H borylation catalysts that should find wide application in the context of C–H functionalization chemistry.

Over the past two decades, the C–H bond activation and functionalization reaction has been known as a prevailing method for the construction of carbon–carbon and carbon–heteroatom bonds using various transition metal catalysts.