Visible light catalyzed reaction of α-bromochalcones with chalcones: direct access to the urundeuvine scaffold

Karki, Bhupal Singh; Pramanik, Mukund M. D.; Kant, Ravi; Rastogi, Namrata

doi:10.1039/c8ob01881b

Cited by 7 publications

(3 citation statements)

References 47 publications

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“… 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 and phenanthrenes derivatives and in the intermolecular coupling of alkenes …”

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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“…In another article, Paria and coworkers [195] revealed a photoredox iridium complex catalyzed intermolecular couplings of α‐bromochalcones to olefins affording 3,4‐dihydronaphthalenes (reaction 5, Figure 49) that can be easily transformed to the corresponding naphthalenes and further cyclized to 5 H ‐benzo[c]fluorenes. Another groupof researchers [196] investigated the visible light catalyzed reaction of α‐Br‐chalcones with α‐unsubstituted chalcones that led to the synthesis of dihydronaphthalenes, which were oxidized to the corresponding naphthalenes (reaction 6, Figure 49). This strategy was employed to prepare derivatives of the natural urundeuvine chalcones.…”

Section: Different α‐Substituted Chalconesmentioning

confidence: 99%

α‐Substituted Chalcones: A Key Review

Al-Rifai

Mubarak

2021

ChemistrySelect

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Chalcones are attractive chemical motifs with various biological activities. Aryl substituted chalcones have been extensively studied and reviewed through the years. However, α‐substituted chalcones have rarely been investigated. Hence, this review highlights the α‐substituted chalcones: their synthetic routes, reported biological activities, and transformations to other organic compounds. To the best of our knowledge, this would be the first comprehensive review about α‐substituted chalcones. α‐Substitution of chalcones represents a promising approach to tune their reactivity since it has a direct influence on their activity as Michael acceptors. Additionally, α‐substitution has its effect on the structure and conformation of chalcones. Altering the reactivity of chalcones by α‐substitution has a great impact on their biological activity.

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“…In a variation of these processes, Rastogi and co-workers subsequently showed that chalcones 19 can also be utilized in such sequences instead of simple alkenes to give rise to dihydronaphthalenes 20 , which could be further dehydrogenated to the corresponding naphthalenes 21 (Scheme ). 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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Visible light catalyzed reaction of α-bromochalcones with chalcones: direct access to the urundeuvine scaffold

Abstract: The α-keto vinyl radicals generated from α-bromochalcones under visible light photoredox catalyzed conditions were trapped by chalcones.

Cited by 7 publications

References 47 publications

Photoredox-Catalyzed C–H Functionalization Reactions

Photoredox-Catalyzed C–H Functionalization Reactions

α‐Substituted Chalcones: A Key Review

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

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