Xifa Yang

Cooperative Co(III)/Cu(II)-Catalyzed C-N/N-N Coupling of Imidates with Anthranils: Access to 1H-Indazoles via C-H Activation.

Cooperative cobalt- and copper-catalyzed C-H activation of imidate esters and oxidative coupling with anthranils allowed efficient synthesis of 1H-indazoles in the absence of metal oxidants. The anthranil acts as a convenient aminating reagent as well as an organic oxidant in this transformation. The copper catalyst likely functions at the stage of N-N formation.

Rhodium(III)-Catalyzed Synthesis of Naphthols via C–H Activation of Sulfoxonium Ylides

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.

Iridium(III)-Catalyzed Synthesis of Benzimidazoles via C–H Activation and Amidation of Aniline Derivatives

Ir(III)-catalyzed synthesis of benzimidazoles has been realized under redox-neutral conditions by annulation of aniline derivatives with dioxazolones. The reaction proceeded via a C-H activation-amidation-cyclization pathway with a decent substrate scope.

Divergent Access to 1-Naphthols and Isocoumarins via Rh(III)-Catalyzed C–H Activation Assisted by Phosphonium Ylide

Rh-catalyzed C-H activation of phenacyl phosphoniums in coupling with α-diazocarbonyl compounds has been realized with the assistance of a mutifunctional phosphonium ylidic directing group, providing expedient accesses to 1-naphthols and isocoumarins. Switchable synthesis of 1-naphthols and isocoumarins was realized by substrate control, where these transformations were enabled by initial C-H activation and subsequent intramolecular Wittig reaction or nucleophilic C-O formation.

Rh(III)-Catalyzed Acceptorless Dehydrogenative Coupling of (Hetero)arenes with 2-Carboxyl Allylic Alcohols

Rhodium(III)-catalyzed C-H activation of (hetero)arenes and redox-neutral coupling with 2-carboxyl allylic alcohols has been realized for the construction of β-aryl ketones. This reaction occurred efficiently at a relatively low catalyst loading via initial dehydrogenative alkylation to give a β-keto carboxylic acid, followed by decarboxylation.

Regio- and Diastereoselective Access to Fused Isoxazolidines via Ru(II)-Catalyzed C–H Activation of Nitrones and Coupling with Perfluoroalkylolefins

The synthsis of fluorinated isoxazolidines in bicyclic settings has been realized via Ru(II)-catalyzed C-H activation of aryl nitrones with perfluoroalkyl-substituted olefins as the coupling partner. The reaction proceeded via initial chelation-assisted C(aryl)-H allylation followed by regio- and diastereoselective intramolecular dipolar addition between the nitrone directing group and the olefin unit.

Rhodium(III)-catalyzed synthesis of indanones via C–H activation of phenacyl phosphoniums and coupling with olefins

Phosphonium ylide acts as an efficient bifunctional directing group in Rh(III)-catalyzed C–H activation of arenes and oxidative coupling with activated olefins, leading to facile construction of indanones via a sequence of oxidative olefination and carboannulation. The phosphonium moiety functions as an oxophilic group, and dephosphination triggers a nucleophilic cyclization.

Access to Quaternary Stereogenic Centers via Rhodium(III)-Catalyzed Annulations between 2-Phenylindoles and Ketenes

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.

Redox-Neutral Access to Isoquinolinones via Rhodium(III)-Catalyzed Annulations of O-Pivaloyl Oximes with Ketenes

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.