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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]

Dioxygen activation with both cyclic (amino)(alkyl)carbenes and di(amino)carbenes at ambient temperature is described. Theoretical studies suggest that electron rearrangement from the doubly filled σ orbital of carbene carbon to its vacant p orbital through the π* antibonding orbital of 3O2 can be considered for Ccarbene–O bond formation. [ABSTRACT FROM AUTHOR]

Described here is a chromium-catalyzed alkylative cross-coupling of benzamide derivatives with aliphatic electrophiles under mild conditions. This reaction was promoted by a low-cost and air-stable chromium(iii) chloride salt combined with an N-heterocyclic carbene ligand and phenylmagnesium bromide as a reductant, and probably occurred with low-valent chromium involved in the catalytic cleavage of the ortho-C–H bonds of the benzamide, followed by coupling with the alkyl bromide through a radical-involving mechanism. [ABSTRACT FROM AUTHOR]

An iron-catalyzed oxidative coupling/cyclization reaction for the synthesis of benzoxazoles at room temperature is reported. This reaction was enabled by an inexpensive iron(iii) catalyst by treating readily available phenol derivatives with benzoyl aldehyde oximes. Mechanistic studies show that benzoyl aldehyde oxime is not only used as a substrate, but also serves as an ancillary ligand to support the iron salt in the promotion of the transformation. [ABSTRACT FROM AUTHOR]

Metal-free synthesis of chalcone derivatives through a tandem cross-dehydrogenative-coupling/elimination reaction is described. A simple and inexpensive ammonium persulfate salt enables the reaction between ketones and benzylamines to proceed with high stereoselectivity and good functional group compatibility. [ABSTRACT FROM AUTHOR]

An efficient and versatile synthetic approach to NHC-based organometallic polymers has been developed by a simple three-step synthesis. A novel brush polymer having imidazolium salt side chains (P2) was firstly synthesized through postpolymerization modification of P1, which permits access to Ag(I)-NHC-based side chain polymer (P3) at room temperature in high yield. P3 was applied as a carbene transfer agent to form a Pd-NHC-containing polymer (P4) by the transmetallation reaction of Ag(I)-NHCs in the side chains. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis indicated that 77% of Ag(I)-NHCs in the side chains of P3 were transmetallated. The resulting Pd-NHC-containing polymer (P4) showed high catalytic activity and reusability in the Suzuki reactions of aryl chlorides and aryl boronic acids. This novel Pd-NHC-containing polymeric catalyst was used five times and still remained active giving the desired biaryl products in 70% yield in the fifth run of the cross-coupling reaction of deactivated 4-chloroanisole with phenylboronic acid.