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Rhodium(III)-catalyzed C-H activation-based arylation of sterically hindered (hetero)arenes has been realized using diazo compounds and triazoles as arylating reagents for atroposelective synthesis of two classes of biaryls. The coupling of 3-substituted indoles and

Rh(III)-catalyzed activation and acylation of sp3 C–H bonds has been realized with diarylcyclopropenone as an acylating reagent. Both benzylic C–H in 8-methylquinolines and unactivated C–H in 2-alkylpyridines are applicable in this C–H acylation reaction, providing enones in good yields under redox-neutral conditions.

Cobalt(III) and rhodium(III) catalysts exhibited complementary scope in C-H amidation of aryl enaminones. The amidation reactions proceeded with broad scope under the assistance of a weakly coordinating and bifunctional enaminone directing group. The electrophilicity of the enaminone group can be further utilized in subsequent hydrolysis-cyclization reactions to afford NH 4-quinolones in telescoping reactions.

Silver-catalyzed nucleophilic addition and intramolecular Friedel–Crafts alkylation between α-oxoketene dithioacetals and tertiary propargylic carbonates have been realized. The reactions proceeded in moderate to good yields with broad substrate scope, providing a straightforward method for the synthesis of substituted indenes.

Vinyl benzoxazinanone was applied as an electrophilic allylating reagent for a series of arenes under redox-neutral Rh(III) catalysis. This reaction occurs in high efficiency under mild conditions to afford allylarenes bearing a sulfonamide functionality in exclusively E-selectivity. This allylation system combines C-H activation of arenes and scission of an unstrained six-membered ring.

Co(III)-catalyzed mild C-C couplings of arenes with strained rings such as 7-oxabenzonorbornadienes and 2-vinyloxirane have been realized. The transformation is proposed to undergo ortho C-H activation, olefin insertion, and subsequent β-oxygen elimination. A broad range of synthetically useful functional groups are compatible, thus providing a new entry to access diversely 2-functionalized indoles.

C-H activation assisted by a bifunctional directing group has allowed the construction of heterocycles. This is ideally catalyzed by earth-abundant and eco-friendly transition metals. We report Co(III)-catalyzed redox-neutral coupling between arenes and alkynes using an NH amide as an electrophilic directing group. The redox-neutral C-H activation/coupling afforded quinolines with water as the sole byproduct.

Chemodivergent coupling of α-acylketene dithioacetals with diazo compounds has been realized under catalyst control. The Ru(II)-catalyzed C–H activation occurred at the olefinic position, and 1:2 coupling with α-diazoketoesters leads to furfurylation. In contrast, the Rh(III)-catalyzed C–H functionalization occurred at both the olefinic and the ortho C(aryl)–H positions, and [4 + 2] annulation afforded naphthalenones. Synthetic applications have been performed to demonstrate the usefulness of the coupling system.

A mild and redox-neutral [4 + 2] annulation of O-pivaloyl oximes with ketenes has been realized for synthesis of quaternary-carbon-stereocenter-containing (QCSC) isoquinolinones, where the N-OPiv not only acts as an oxidizing group but also offers coordination saturation to inhibit protonolysis. The reaction mechanism has been studied by DFT calculations.

Rh(III)-catalyzed C–H activation of arenes and mild oxidative [4 + 2] annulative coupling with ketenes have been realized. The uniquely high reactivity of the C(3) of 2-phenylindoles was successfully utilized to facilitate the reductive elimination process, leading to efficient synthesis of cyclic products with a quaternary carbon stereocenter.

An efficient synthesis of disubstituted acrylic acids has been realized via Rh(III)-catalyzed C–H activation of (hetero)arenes and coupling with four-membered methyleneoxetanones under redox-neutral conditions. In most cases, the reactions are silver-free, and the products are exclusively E-selective with a broad substrate scope. The transformation proceeds via ortho C–H activation followed by selective olefin insertion and β-oxygen elimination.

Direct and efficient synthesis of 1-naphthols has been realized via Rh(III)-catalyzed C–H activation of sulfoxonium ylides and subsequent annulation with alkynes, where the sulfoxonium ylide functioned as a new traceless bifunctional directing group. This reaction occurred under redox-neutral conditions with a broad substrate scope.

A cobalt(III)-catalyzed α-fluoroalkenylation of different arenes with readily available gem-difluorostyrenes has been realized under mild and redox-neutral conditions. This reaction occurs via a C–H activation pathway and offers a step-economical access to various 1,2-diaryl-substituted monofluoroalkenes in excellent Z selectivity in moderate to excellent yields.

Rhodium(III)-catalyzed C–H activation of heteroarenes and functionalization with bifunctional substrates such as anthranils allows facile construction of quinoline-fused heterocycles under redox-neutral conditions. The couplings feature broad substrate scope and provide step-economical access to two classes of quinoline-fused condensed heterocycles.