Synthesis of Phenanthrenes through Visible‐Light Photoredox Catalyzed Intramolecular Cyclization of α‐Bromochalcones

Nagode, Savita B.; Kant, Ravi; Rastogi, Namrata

doi:10.1002/ejoc.201800011

Cited by 8 publications

(10 citation statements)

References 56 publications

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“…115 A subsequent intermolecular and intramolecular cascade reaction with a heteroarene, such as furans, benzofurans, pyrroles, and indoles generates polycyclic heteroarenes (36.3) in high yields. The intramolecular reductive cyclization of α-bromochalcones has since been extended in the synthesis of urundeuvine 116 and phenanthrenes derivatives 117 and in the intermolecular coupling of alkenes. 118 Accessed via Acyl Radical.…”

Section: Inorganic/organometallic Photoredox-catalyzed C−h Functional...mentioning

confidence: 99%

Photoredox-Catalyzed C–H Functionalization Reactions

2021

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The fields of C–H functionalization and photoredox catalysis have garnered enormous interest and utility in the past several decades. Many different scientific disciplines have relied on C–H functionalization and photoredox strategies including natural product synthesis, drug discovery, radiolabeling, bioconjugation, materials, and fine chemical synthesis. In this Review, we highlight the use of photoredox catalysis in C–H functionalization reactions. We separate the review into inorganic/organometallic photoredox catalysts and organic-based photoredox catalytic systems. Further subdivision by reaction classeither sp2 or sp3 C–H functionalizationlends perspective and tactical strategies for use of these methods in synthetic applications.

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Section: Inorganic/organometallic Photoredox-catalyzed C−h Functional...mentioning

confidence: 99%

Photoredox-Catalyzed C–H Functionalization Reactions

2021

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“…The authors have cited additional references within the Supporting Information. [17][18][19][20][21][22][23][24][25][26][27]…”

Section: Supporting Informationmentioning

confidence: 99%

Photocatalytic Electrocyclization for the Synthesis of Dihydrophenanthrenes

Singh,

Kant,

Tripathi

2024

Asian J Org Chem

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“…In this way, the intramolecular cyclization of vinyl radicals 23 was possible, enabling the synthesis of substituted phenanthrenes 25. 60 Moving from α-bromochalcones 12 to α-bromocinnamates 26 goes along with a significant increase in reduction potential, which is a consequence of the smaller conjugated π system (E RX/RX •− °= −0.88 V vs SCE for α-bromochalcone 12 and −1.54 V vs SCE for 26-Br), thereby requiring strongly reducing photocatalysts in their oxidative quenching cycle (Scheme 9). Thus, the highly reducing PC2 (E M + /M* °= −1.73 V vs SCE) was envisioned to be suitable for the coupling of such substrates.…”

Section: Generation Of Vinyl Radicals By Photoelectron Transfer and T...mentioning

confidence: 99%

“… Moreover, rather than by trapping with an external heteroarene, cyclization into an arene placed at an appropriate position of the α-bromochalcone can also be achieved. In this way, the intramolecular cyclization of vinyl radicals 23 was possible, enabling the synthesis of substituted phenanthrenes 25 …”

Section: Activation Of Vinyl Halides By Visible-light Photocatalysismentioning

confidence: 99%

Shining Visible Light on Vinyl Halides: Expanding the Horizons of Photocatalysis

2020

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Conspectus Over the past decade, photoredox catalysis has blossomed as a powerful methodology because of its wide applicability in sustainable free-radical-mediated processes, in which light is used as a cleaner energy source to alter the redox properties of organic molecules and to drive unique chemical transformations. Numerous examples of highly selective C–C and C–heteroatom bond formation processes have been achieved this way in an efficient and waste-reducing way. Therein, the activation of widely available organic halides via single-electron reduction has been broadly applied for organic synthesis. However, in comparison with alkyl and aryl halides, the analogous utilization of vinyl halides is less developed, most likely as a consequence of the highly unstable vinyl radicals generated as intermediates along with their strong tendency to abstract hydrogen atoms from a suitable source (e.g., the solvent), resulting in a synthetically less useful reduction. Nevertheless, during the last years, a number of photocatalytic processes involving vinyl halides have been developed, featuring the generation of vinyl radicals, diradicals, or radical cations as the key transient species. Moreover, photoredox processes in which a radical reacts with a vinyl halide or with an in situ-generated vinylmetal halide have been developed. Thus, identifying suitable conditions to generate and manipulate these reactive species has resulted in novel synthetic processes in a controllable manner. Moreover, in view of the great versatility of vinyl halides in palladium-catalyzed cross-coupling reactions, their activation by visible light might provide an attractive alternative to such processes, especially when non-noble metals could be used as photoinitiators in the future. In this Account, we discuss the various strategies of photoredox processes involving vinyl halides, classifying the material into four categories: (a) formation of a vinyl radical upon receipt of an electron from the photocatalyst, (b) formation of a radical cation after donation of an electron to the photocatalyst, (c) energy transfer corresponding to diradical formation upon triplet–triplet sensitization, and (d) dual transition metal and photocatalysis employing vinyl halides as precursors. While in the first three approaches the activation of vinyl halides is part of the photochemical step, the fourth one involves the interaction of a photochemically generated radical with a vinylnickel(II) halide obtained in turn by the oxidative addition of nickel(0) to the vinyl halide. Therefore, we highlight these important developments for conceptual comparison to the direct activation of vinyl halides by light, but they are not covered in depth in this Account.

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Synthesis of Phenanthrenes through Visible‐Light Photoredox Catalyzed Intramolecular Cyclization of α‐Bromochalcones

Cited by 8 publications

References 56 publications

Photoredox-Catalyzed C–H Functionalization Reactions

Photoredox-Catalyzed C–H Functionalization Reactions

Photocatalytic Electrocyclization for the Synthesis of Dihydrophenanthrenes

Shining Visible Light on Vinyl Halides: Expanding the Horizons of Photocatalysis

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