A switchable redox annulation of 2-nitroarylethanols affording <i>N</i>-heterocycles: photoexcited nitro as a multifunctional handle

Wang, Bin; Ren, Hongyuan; Cao, Hou-Ji; Lu, Changsheng; Yan, Hong

doi:10.1039/d2sc03590a

Cited by 24 publications

(16 citation statements)

References 72 publications

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“…These byproducts, which form as the nitroarene is consumed and are present at the end of the reaction, are presumably formed via condensation of in situ-formed aniline and N-hydroxyaniline with nitrosoarene. 12 , 24 Markedly, observation of these byproducts illustrates that fragmentation of the radical recombination product (12) leads to the desired C-H hydroxylation products (2) and the nitrosoarene byproduct.…”

Section: A Oxidative C-h Hydroxylationmentioning

confidence: 99%

“…Recently, Cao, Lu, and Yan disclosed that photoexcited baryl substituted nitroarenes can trigger an intramolecular OAT event leading to tertiary diarylalcohols. 12 Although both approaches are of significant novelty, they suffer from limited reaction scope and issues with overoxidation. Based on the capability of photogenerated nitroarenes to serve as the C-H bond activator and the oxygen atom source, we questioned whether a selective, intermolecular, anaerobic C-H hydroxylation of aliphatic precursors could be achieved under visible light irradiation.…”

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confidence: 99%

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Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Paolillo

Duke

Gogarnoiu

et al. 2022

Preprint

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A photoexcited nitroarene-mediated, anaerobic C–H hydroxylation of aliphatic systems is reported. The success of this reaction is due to the bifunctional nature of the photoexcited nitroarenes, which serve as the C–H bond activator and the oxygen atom source. Compared to previous methods, this approach is cost and atom economical due to the commercial availability of the nitroarene, the sole mediator of the reaction. Owing to the anaerobic conditions of the transformation, a noteworthy expansion in substrate scope can be obtained compared to prior reports. Mechanistic studies support that the photoexcited nitroarenes engage in successive hydrogen atom transfer and radical recombination events with hydrocarbons, leading to N-arylhydroxylamine ether intermediates. Spontaneous fragmentation of these intermediates leads to the key oxygen atom transfer products.

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Section: A Oxidative C-h Hydroxylationmentioning

confidence: 99%

mentioning

confidence: 99%

Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Paolillo

Duke

Gogarnoiu

et al. 2022

Preprint

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“…Recently, Cao, Lu, and Yan disclosed that photoexcited b-aryl substituted nitroarenes can trigger an intramolecular OAT event leading to tertiary diarylalcohols. 13 Although both approaches are of significant novelty, they suffer from limited reaction scope and issues with overoxidation. Based on the capability of photogenerated nitroarenes to serve as the C-H bond activator and the oxygen atom source, we questioned whether a selective, intermolecular, anaerobic C-H hydroxylation of aliphatic precursors could be achieved under visible light irradiation.…”

mentioning

confidence: 99%

“…Further support for 9 was acquired via high-resolution mass spectrometry studies (HRMS) of the crude reaction mixture. The azoarene (13) and azoxyarene ( 14) byproducts were isolated from the reaction mixture of 2ag and characterized by NMR and HRMS (Scheme 3). These byproducts, which form as the nitroarene is consumed and are present at the end of the reaction, are presumably generated via condensation of in situ-formed aniline and N-hydroxyaniline with nitrosoarene.…”

mentioning

confidence: 99%

“…These byproducts, which form as the nitroarene is consumed and are present at the end of the reaction, are presumably generated via condensation of in situ-formed aniline and N-hydroxyaniline with nitrosoarene. 13,26 Markedly, observation of these side products illustrates that fragmentation of the radical recombination product (12) leads to the desired C-H hydroxylation products (2) and the nitrosoarene byproduct.…”

mentioning

confidence: 99%

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Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Paolillo

Duke

Gogarnoiu

et al. 2023

Preprint

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Modular Photochemical Flow Synthesis of Structurally Diverse Benzyne and Triazine Precursors

García-Lacuna

Baumann

2023

Adv Synth Catal

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Benzyne and related arynes are classical high‐energy species with a rich history of widespread applications in synthesis. However, despite several synthetic routes being available to generate arynes and their precursors, none represents an ideal entry to benzyne chemistry in view of safety, scalability, and sustainability. Here we report a new photochemical flow process allowing for the generation of benzyne precursors in high yields, and throughput, with easy isolation of multigram quantities of products. This process leverages a catalyst‐free photochemical rearrangement via a photoexcited nitro arene which involves a cyclic hydroxylamine intermediate that has been fully characterized. The resulting precursors were converted to benzynes via a second photochemical flow process generating heterocyclic targets upon trapping with azide and sydnone partners. Remarkably, when reacting the benzyne precursors with secondary amines, a wide range of aryl triazines is obtained in good yields via a third photo‐flow transformation. This represents a modular approach to synthesize these species, that avoids the use of potentially explosive diazonium salts. Ultimately, three photochemical flow processes using a single high‐power LED light source (365 nm, adjustable in‐put power) are presented with manifest benefits compared to batch processing. Moreover, the functionalization of a pendent carboxyl group to form sets of biologically relevant aryl triazine‐based amides highlights further applications of these unique and industrially relevant triazine entities.

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A switchable redox annulation of 2-nitroarylethanols affording N-heterocycles: photoexcited nitro as a multifunctional handle

Abstract: The efficient transformation of nitroaromatics to functional molecules such as N-heterocycles has been an attractive and significant topic in synthesis chemistry. Herein, a photoexcited nitro-induced strategy for switchable annulation of...

Cited by 24 publications

References 72 publications

Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Anaerobic Hydroxylation of C(sp3)–H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes

Modular Photochemical Flow Synthesis of Structurally Diverse Benzyne and Triazine Precursors

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