Metalloradical activation of carbonyl azides for enantioselective radical aziridination

Riart-Ferrer, Xavier; Sang, Peng; Tao, Jingran; Xu, Hao; Jin, Li‐Mei; Lü, Hongjian; Cui, Xin; Wojtas, Łukasz; Zhang, X. Peter

doi:10.1016/j.chempr.2021.03.001

Cited by 38 publications

(23 citation statements)

References 111 publications

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“…To the best of our knowledge, this result represents the first example of a nitrenoid insertion-mediated carbon rearrangement for the alkyl moiety in aromatic systems. Since the catalytic amidation efficiency is significantly influenced by the electrophilicity of metal–nitrenoid species, − the electronic properties of the κ 2 -N,O-ligands were modulated next to accomplish satisfactory reactivity. When the electron-donating t -Bu group was introduced at the C5 position of a quinolinol ligand, an adverse effect was observed ( Co2 , 23%), whereas an electron-withdrawing NO 2 analogue improved the catalytic activity ( Co3 , 74%).…”

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confidence: 99%

Cobalt–Nitrenoid Insertion-Mediated Amidative Carbon Rearrangement via Alkyl-Walking on Arenes

et al. 2021

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We herein disclose the Cp*Co(III)(LX)-catalyzed amidative alkyl migration using 2,6-disubstituted phenyl azidoformates. Upon the cobalt–nitrenoid insertion toward the substituted ortho carbon, an arenium cationic species bearing a quaternary carbon is generated, and a subsequent alkyl migration process is suggested to occur through an unforeseen alkyl-walking mechanism. A quinolinol ligand of the cobalt catalyst system is proposed to facilitate the final product-releasing rearomatization process by serving as an internal base. This new mechanistic mode enabled both [1,2]- and [1,4]-alkyl rearrangements to allow the structural variation of N-heterocyclic compounds.

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confidence: 99%

Cobalt–Nitrenoid Insertion-Mediated Amidative Carbon Rearrangement via Alkyl-Walking on Arenes

et al. 2021

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“…The homocoupling of ortho-substituted aryl azides [35,44] was ascribed to the capacity of cobalt porphyrin species to assist H-atom transfer (HAT) [45][46] reactions through the well-known formation of radical nitrene intermediates. [47][48][49][50] As reported by B. De Bruin and co-authors [35,44] the radical nitrene B, formed by the reaction of Co(porphyrin) A with azide, can abstract a hydrogen atom from the vicinal YH substituent forming the reactive intermediate C, whose homocoupling reaction affords phenoxizinones or azobenzenes depending if Y is an O or NH functionality, respectively (Scheme 2).…”

Section: Introductionmentioning

confidence: 85%

“…Among the reported procedures, [31–35] those mediated by cobalt(II) porphyrins, efficient catalysts in promoting the aryl azide activation, [29,36–43] represent interesting methods to synthesise azobenzenes. The homocoupling of ortho ‐substituted aryl azides [35,44] was ascribed to the capacity of cobalt porphyrin species to assist H‐atom transfer (HAT) [45–46] reactions through the well‐known formation of radical nitrene intermediates [47–50] . As reported by B.…”

Section: Introductionmentioning

confidence: 94%

Cobalt Porphyrin‐Catalysed Synthesis of Azobenzenes by Dehydrogenative Coupling of Anilines

et al. 2022

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The demand for azobenzenes has exponentially grown due to their wide range of applications in textile, medical, and dye industries. Here we report a procedure to synthesise azobenzenes by the dehydrogenative coupling of anilines in the presence of CoII(TPP) (TPP=dianion of tetraphenyl porphyrin) catalyst and 4‐nitrophenyl azide oxidant species. Differently substituted azobenzenes were obtained in yields up to 72 % together with 4‐nitrophenyl amine, which is the stoichiometric by‐product of the process. The procedure displayed a good sustainability due to the almost quantitative recovery of pure 4‐nitrophenyl amine that can be transformed again into the desired azide to pave the way for an efficient circular process. Experimental data supported the occurrence of a radical mechanism mediated by putative nitrene radical cobalt intermediate.

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“…Zhang and coworkers elaborated a method to produce Nsubstituted aziridines in a cobalt-mediated radical process. [13] The asymmetric cyclization conducted in the presence of Co II ligand 6 enables product formation in high yields and with excellent enantioselectivities under mild conditions (Scheme 7). In contrast, (1-fluorovinyl)benzene and methyl or ethyl acrylate gave lower productivities (32-43 %, 48-82 % ee).…”

Section: Cobalt-catalyzed Processesmentioning

confidence: 99%

Stereoselective Synthesis of Azacycles Induced by Group 8–11 Late Transition Metals

Molnár

2021

Eur J Org Chem

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The aim of the present minireview is to summarize and discuss recent advances in the field of stereoselective synthesis of azacycles. The focus is on studies that appeared in the last two years to illustrate recent trends with a handful of examples from 2019 highlighting an important field of enantioselective chemistry. Results collected and discussed here show that syntheses catalyzed by late transition metals of group 8-11 afford products in high yield with high stereoselectivity, often under mild reaction conditions thereby demonstrating their efficacy to afford valuable products. Plausible reaction mechanisms for most transformations are also discussed.

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Metalloradical activation of carbonyl azides for enantioselective radical aziridination

Cited by 38 publications

References 111 publications

Cobalt–Nitrenoid Insertion-Mediated Amidative Carbon Rearrangement via Alkyl-Walking on Arenes

Cobalt–Nitrenoid Insertion-Mediated Amidative Carbon Rearrangement via Alkyl-Walking on Arenes

Cobalt Porphyrin‐Catalysed Synthesis of Azobenzenes by Dehydrogenative Coupling of Anilines

Stereoselective Synthesis of Azacycles Induced by Group 8–11 Late Transition Metals

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