Enantiomeric access to pentatomic biaryls is challenging due to their relatively low rotational barrier. Reported herein is the mild and highly enantioselective synthesis of 2,3′-biindolyls via underexplored integration of C−H activation and alkyne cyclization using a unified chiral Rh(III) catalyst. The reaction proceeded via initial C−H activation followed by alkyne cyclization. A chiral rhodacyclic intermediate has been isolated from stoichiometric C−H activation, which offers direct mechanistic insight.

Cascade reactions initiated by radical addition to alkynes are synthetically very attractive because they enable access to highly complex molecular skeletons in only few synthetic steps under usually mild conditions. Here we report a general radical cascade reaction of alkynes, N-fluoroarylsulfonimides and alcohols, enabling the efficient synthesis of important α-amino-α-aryl ketones from readily available starting materials via a single operation. During this process, the highly regioselective nitrogen-centred radical addition to internal and terminal alkynes generating vinyl radicals and the next explicit migration of aryl group from the nitrogen source lead the following efficient desulfonylation, oxygenation, and semi-pinacol rearrangement. In addition, the semi-pinacol rearrangement precursors, α-alkyloxyl-α,α-diaryl imines, could also be efficiently obtained under milder conditions. This methodology might open a new entry for designing intermolecular radical cascade reaction of alkynes.

Sulfoxonium ylides act as an efficient carbene precursor in rhodium(III)-catalyzed C-H acylmethlyation of a variety of arenes assisted by different chelating groups, and both aryl- and alkyl-substituted β-carbonyl sulfoxonium ylides are applicable. The system proceeded under redox-neutral conditions with a broad scope, high efficiency, and functional group tolerance.

Chemodivergent and redox-neutral annulations between N-methoxybenzamides and sulfoxonium ylides have been realized via Rh(iii)-catalyzed C-H activation. The sulfoxonium ylide acts as a carbene precursor, and coupling occurs under acid-controlled conditions, where Zn(OTf) and PivOH promote chemodivergent cyclizations.

Sulfoxonium ylides acts as a bifunctional C2-synthon in Rh(iii)-catalyzed redox-neutral annulative coupling with arenes for the synthesis of N-heterocycles and carbocycles.

Reported herein is the atroposelective synthesis of biaryl NH isoquinolones by RhIII‐catalyzed C−H activation of benzamides and intermolecular [4+2] annulation for a broad scope of 2‐substituted 1‐alkynylnaphthalenes, as well as sterically hindered, symmetric diarylacetylenes. The axial chirality is constructed based on dynamic kinetic transformation of the alkyne in redox‐neutral annulation with benzamides, with alkyne insertion being stereodetermining. The reaction accommodates both benzamides and heteroaryl carboxamides and proceeds in excellent regioselectivity (if applicable) and enantioselectivities (average 91.8 % ee). An enantiomerically and diastereomerically pure rhodacyclic complex was prepared and offers insight into enantiomeric control of the coupling system, wherein the steric interactions between the amide directing group and the alkyne substrate dictate both the regio‐ and enantioselectivity.

An efficient, atom-economical, and regioselective insertion of indoles into terminal alkynes has been realized via cobalt­(III)-catalyzed C–H activation under mild conditions, leading to efficient synthesis of α-gem-vinylindoles. The insertion of the alkynes follows a rare 1,2-selectivity, and silyl alkynes, alkyl alkynes, propargyl alcohols, and protected propargyl amines are all applicable. The mechanism of this hydroarylation system has been studied in detail by a combination of experimental and computational approaches. In the reaction of silyl terminal alkynes, the regioselectivity is dictated by the steric effects of the alkyne substituent, especially in the protonolysis stage. However, for protected propargyl amines, the selectivity results from electronic effects during the insertion step, with protonolysis being insignificant in the determination of selectivity. An internal alkyne also coupled in high efficiency but with low regioselectivity. Comparisons of cobalt, rhodium, and iridium catalysts have also been made in terms of regioselectivity and reactivity, and both are high for cobalt catalysts.

Chiral rhodium(III) cyclopentadienyl catalysts (CpXRhIII) play significant roles in asymmetric arene C−H activation. Rh/Ir‐catalyzed couplings of arenes and strained rings have been well‐studied, but they have been limited to racemic systems. Reported in this work is the CpxRhIII/AgSbF6‐catalyzed enantioselective desymmetrizative C−C coupling of N‐pyrimidylindoles and 7‐azabenzonorbornadienes with high efficiency and enantioselectivity. The role of AgSbF6 has been established by mechanistic studies. AgSbF6 enhances the catalytic activity by suppressing the C3−H activation of the indoles, activation which would otherwise lead to catalytically inactive species.