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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. [ABSTRACT FROM AUTHOR]

Described here is the chromium-catalyzed cleavage of C(aryl)–SMe bonds leading to coupling with organomagnesium to give functionalized benzaldehydes under mild conditions. This reaction was promoted specifically by a low-cost and simple CrCl2 salt used as a precatalyst, enabling synchronous activations of ortho-C(aryl)–SMe and ortho′-C(aryl)–H bonds to achieve difunctionalization of benzaldimines. This work provided a strategy for accessing arylated, alkylated, and diarylated benzaldehyde derivatives as a result of the couplings of C(aryl)–SMe and C(aryl)–SMe/C(aryl)–H bonds promoted with cost-effective Cr catalysis. [ABSTRACT FROM AUTHOR]