Rhodium(III)-Catalyzed C–C Coupling of Arenes with 2‑Vinyloxiranes: Synthesis of Allylic Alcohols

A rhodium­(III)-catalyzed C–C coupling between 2-vinyloxiranes and arenes directed by different chelating groups has been realized via a C–H activation pathway. This reaction proceeded under conditions with a low catalyst loading, and allylic alcohols were isolated as the coupling products. A series of benzoazepanes has been synthesized by following this coupling

Mild Synthesis of Chalcones via Rhodium(III)-Catalyzed C–C Coupling of Arenes and Cyclopropenones

A Rh­(III)-catalyzed aryl C–H bond insertion into cyclopropenones via a C–H activation pathway has been reported. A series of arenes bearing directing groups such as 2-pyridyl, 2-pyrimidyl, <i>N</i>-pyrazyl, and oxime can be applicable, providing chalcones in excellent yields under mild conditions. Several possible Rh­(III) intermediates in this reaction were investigated

Mild Synthesis of Chalcones via Rhodium(III)-Catalyzed C–C Coupling of Arenes and Cyclopropenones

A Rh­(III)-catalyzed aryl C–H bond insertion into cyclopropenones via a C–H activation pathway has been reported. A series of arenes bearing directing groups such as 2-pyridyl, 2-pyrimidyl, <i>N</i>-pyrazyl, and oxime can be applicable, providing chalcones in excellent yields under mild conditions. Several possible Rh­(III) intermediates in this reaction were investigated

Cobalt-Catalyzed Asymmetric Hydroboration/Cyclization of 1,6-Enynes with Pinacolborane

We report a cobalt-catalyzed asymmetric hydroboration/cyclization of 1,6-enynes with catalysts generated from Co­(acac)₂ and chiral bisphosphine ligands and activated in situ by reaction with pinacol­borane (HBpin). A variety of oxygen-, nitrogen-, and carbon-tethered 1,6-enynes underwent this asymmetric transformation, yielding both alkyl- and vinyl-substituted boronate esters containing chiral tetrahydrofuran, cyclopentane, and pyrrolidine moieties with high to excellent enantio­selectivities (86%–99% ee)

Rh(III)-Catalyzed Oxidative Annulation of 2‑Phenylimidazo[1,2‑<i>a</i>]pyridines with Alkynes: Mono versus Double C–H Activation

Rh­(III)-catalyzed C–H activation of 2-phenylimidazo­[1,2-<i>a</i>]­pyridines in divergent oxidative coupling with alkynes has been achieved. Selective mono versus 2-fold C–H activation has been attained under condition control. When AgOAc was used as an oxidant, the coupling afforded 5,6-disubstituted naphtho­[1′,2′:4,5]­imidazo­[1,2-<i>a</i>]­pyridines as a result of initial nitrogen chelation-assisted C–H activation at the benzene ring followed by rollover C–H activation. In contrast, the reaction afforded a fused isoquinolinium salt as a result of C–C and C–N coupling when AgBF₄ was employed as a co-oxidant. A rhodacyclic intermediate has been isolated

Rh(III)-Catalyzed Oxidative Annulation of 2‑Phenylimidazo[1,2‑<i>a</i>]pyridines with Alkynes: Mono versus Double C–H Activation

Rh­(III)-catalyzed C–H activation of 2-phenylimidazo­[1,2-<i>a</i>]­pyridines in divergent oxidative coupling with alkynes has been achieved. Selective mono versus 2-fold C–H activation has been attained under condition control. When AgOAc was used as an oxidant, the coupling afforded 5,6-disubstituted naphtho­[1′,2′:4,5]­imidazo­[1,2-<i>a</i>]­pyridines as a result of initial nitrogen chelation-assisted C–H activation at the benzene ring followed by rollover C–H activation. In contrast, the reaction afforded a fused isoquinolinium salt as a result of C–C and C–N coupling when AgBF₄ was employed as a co-oxidant. A rhodacyclic intermediate has been isolated

Cobalt-Catalyzed Asymmetric Hydroboration/Cyclization of 1,6-Enynes with Pinacolborane

We report a cobalt-catalyzed asymmetric hydroboration/cyclization of 1,6-enynes with catalysts generated from Co­(acac)₂ and chiral bisphosphine ligands and activated in situ by reaction with pinacol­borane (HBpin). A variety of oxygen-, nitrogen-, and carbon-tethered 1,6-enynes underwent this asymmetric transformation, yielding both alkyl- and vinyl-substituted boronate esters containing chiral tetrahydrofuran, cyclopentane, and pyrrolidine moieties with high to excellent enantio­selectivities (86%–99% ee)

Rh(III)-Catalyzed Synthesis of <i>N</i>‑Unprotected Indoles from Imidamides and Diazo Ketoesters via C–H Activation and C–C/C–N Bond Cleavage

The synthesis of <i>N</i>-unprotected indoles has been realized via Rh­(III)-catalyzed C–H activation/annulation of imidamides with α-diazo β-ketoesters. The reaction occurs with the release of an amide coproduct, which originates from both the imidamide and the diazo as a result of CN cleavage of the imidamide and C–C­(acyl) cleavage of the diazo. A rhodacyclic intermediate has been isolated and a plausible mechanism has been proposed

Rhodium(III)-Catalyzed C–H Activation and Amidation of Arenes Using <i>N</i>‑Arenesulfonated Imides as Amidating Reagents

Rhodium(III)-catalyzed C–H activation–amidation of arenes bearing chelating groups has been achieved using <i>N</i>-arenesulfonated imides as efficient amidating reagents without using any base additive. Pyridine, oxime, and pyrimidine proved to be viable directing groups

Rh(III)-Catalyzed Selenylation of Arenes with Selenenyl Chlorides/Diselenides via C–H Activation

Rh­(III)-catalyzed, chelation-assisted C–H activation and selenylation of arenes has been achieved. Arenes bearing oxime, azo, pyridyl, and <i>N</i>-oxide chelating groups are viable substrates, and electrophilic selenyl chlorides and diselenides are used as selenylating reagents. The catalytic system is highly efficient under mild conditions over a broad range of substrates with excellent functional group tolerance