Cr-catalyzed borylation of C(aryl)–F bonds using a terpyridine ligand.

The defluoroborylation of fluoroarenes by chromium-catalyzed cleavage of unactivated C–F bonds is described. The reaction uses HBpin as the boron source, low-cost and commercially available chromium salt as the precatalyst, and terpyridine as a crucial ligand, providing a protocol with atom-efficient benefits and a wide range of applicable substrates for the functionalization of aryl C–F bonds. Preliminary mechanistic studies indicate that an unprecedented Cr-catalyzed magnesiation of the unactivated C–F bond occurred. The generated arylmagnesium intermediates then participated in the subsequent borylation reaction. The application of the strategy in the preparation of valuable derivatives is demonstrated by the late-stage functionalization of boronate ester groups. [ABSTRACT FROM AUTHOR]