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

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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.