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Control of regioselectivity that defies the intrinsic reactivity of arene C–H bonds remains a formidable challenge. In this work, dimeric Rh(II) complexes have been applied as an efficient catalyst...

Chiral RhIII catalysts can catalyze the asymmetric [4+1] spiroannulation of O-pivaloyl oximes with α-diazo homophthalimides under redox-neutral and acid/base-neutral conditions, leading to formation of chiral spirocyclic imines as a result of C–H activation and N–O cleavage. The reaction proceeded with high efficiency and features broad substrate scope, mild reaction conditions, and high to excellent enantioselectivities.

C-H bond activation has been established as an attractive strategy to access axially chiral biaryls, and the most straightforward method is direct C-H arylation of arenes. However, the arylating source has been limited to several classes of reactive and bulky reagents. Reported herein is rhodium-catalyzed 1:2 coupling of diarylphosphinic amides and diarylacetylenes for enantio- and diastereoselective construction of biaryls with both central and axial chirality. This twofold C-H activation reaction stays contrast to the previously explored Miura-Satoh type 1:2 coupling of arenes and alkynes in terms of chemoselectivity and proceeded under mild conditions with the alkyne acting as a rare arylating reagent. Both C-H activation events are stereo-determining and are under catalyst control, with the 2nd C-H activation being diastereo-determining in a remote fashion. Analysis of the stereochemistries of the major and side products suggests moderated enantioselectivity of the initial C-H activation-desymmetrization process. However, the minor stereoisomeric (R) intermediate is consumed more readily in undesired protonolysis, eventually resulting in high enantio- and diastereoselectivity of the major product.

Reported herein is the rhodium(III)-catalyzed C-H activation of anilines bearing an N-isoquinolyl directing group for oxidative [3+2] annulation with four classes of internal alkynes, leading to atroposelective indole synthesis via dynamic kinetic annulation with C-N reductive elimination constituting the stereo-determining step. This reaction proceeds under mild conditions with high regio- and enantioselectivity and functional group compatibility.

Rhodium(iii)-catalyzed C-C coupling of heteroarenes and fluorinated α-diazo diketones has been realized for the facile synthesis of 3-arylchromones. The reaction proceeds via chelation-assisted C-H activation, carbene insertion, and uncatalyzed intramolecular nucleophilic aromatic substitution, with C-F cleavage being accommodated in the nucleophilic aromatic substitution step. Three classes of heteroarenes have been defined with decent functional group tolerance.

Rhodium(III)-catalyzed mild and oxidative [4+1] spiroannulation has been realized via C–H activation of oximes and benzoic acids with 1-diazonaphthelen-2(1H)-ones as coupling reagents. This transformation integrates C–H activation and dearomatization and provides a direct approach to spirocyclic isoindole N-oxides and isobenzofuranones with functional group tolerance.

Axial-to-central chirality transfer is an important strategy to construct chiral centers, where the axially chiral reagents are mostly limited to atropomerically stable ones. Reported herein is a RhIII -catalyzed enantioselective spiroannulative synthesis of nitrones. The coupling proceeds via C-H arylation to give an atropomerically metastable biaryl, followed by intramolecular dearomative trapping under oxidative conditions with high degree of chirality transfer.

A rhodium-catalyzed C-H amination of benzamides and isoquinolones with anthranils has been realized under assistance of a weakly coordinating tertiary amide, leading to a bifunctional amination product bearing a proximal carbonyl group. N-benzoylpyrrolidine and N-substituted isoquinolones are two classes of amides that are applicable. The aminated products can further cyclize to acridine under in situ or ex situ conditions.

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.

An efficient synthesis of 2-substituted quinolines from readily available cyclopropanols and imidamides has been developed, where the cyclopropanol acts as a C3 synthon. With the assistance of a bifunctional imidamide directing group, the reaction occurred via sequential C–H/C–C cleavage and C–C/C–N bond formation.

Carbonyl groups are ubiquitous in functional molecules. Although C–H bond acylation has been well-studied via different mechanisms, transition-metal-catalyzed redox-neutral C(sp3)–H acylation under mild conditions is unprecedented. In this work, ketene is designed as a acylating reagent for both C(sp3)–H and C(sp2)–H bonds under Rh(III) catalysis, affording a diverse array of carbonyl compounds in high yields and high atom economy under mild conditions.

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.

Rhodium-catalyzed C–H activation of arenes has been established as an important strategy for the rapid construction of new bonds. On the other hand, ring-opening of readily available cyclopropanols has served as a driving force for the coupling with various nucleophiles and electrophiles. Nevertheless, these two important areas evolved separately, and coupling of arenes with cyclopropanols via C–H activation has been rarely explored. In this work, the oxidative coupling between arenes and cyclopropanols has been realized with high efficiency and selectivity under Rh(III)-catalysis, providing an efficient route to access β-aryl ketones. Moreover, the C–H bond has been extended to benzylic C–H bonds.

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.

Rhodium(III)-catalyzed mild benzylic α-fluoroalkenylation of 8-methylquinolines with gem-difluorostyrenes has been developed. This reaction occurred via C–H activation and C–F cleavage and is applicable to a wide range of substrates, leading to the synthesis of Z-alkenyl fluorides under mild and redox-neutral conditions with high regio- and stereoselectivity.

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.

Rh(III)-catalyzed synthesis of mesoionic heterocycles has been achieved via C–H activation of sydnones and oxidative coupling with internal alkynes. This reaction occurred under mild conditions with high efficiency, broad substrate scope, and low catalyst loading. Moreover, synthetic applications of a coupled product have been demonstrated in the late-stage derivatization into a variety of highly functionalized scaffolds.

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.

The rhodium(III)-catalyzed regioselective alkylation of (hetero)arenes using cyclopropanols as a reactive and efficient coupling partner under oxidative conditions has been developed. This coupling occurred at room temperature via C–H activation of arenes and C–C cleavage of cyclopropanols. Various types of (hetero)arenes (indolines, carbazole, tetrahydrocarbazole, pyrrole, thiophene, etc.) were all successfully reacted under the present conditions. This protocol provides the facile and efficient construction of C7-alkylated indoline scaffolds.

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.

The rhodium(III)-catalyzed regioselective alkylation of (hetero)arenes using cyclopropanols as a reactive and efficient coupling partner under oxidative conditions has been developed. This coupling occurred at room temperature via C–H activation of arenes and C–C cleavage of cyclopropanols. Various types of (hetero)arenes (indolines, carbazole, tetrahydrocarbazole, pyrrole, thiophene, etc.) were all successfully reacted under the present conditions. This protocol provides the facile and efficient construction of C7-alkylated indoline scaffolds.