Light-driven Radical-polar Crossover Catalysis Enabling Decarboxylative Fluorination of Redox Active Esters

Takekawa, Yunosuke; Kodo, Taiga; Nagao, Kazunori; Kakei, Hiroyuki; Takeuchi, Kohei; Sasaki, Yoshiyuki; Ohmiya, Hirohisa

doi:10.1246/cl.220472

Cited by 7 publications

(7 citation statements)

References 36 publications

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“…Intermolecular hydroacylation is the insertion of an alkene into a formyl C−H bond of an aldehyde to produce a ketone in a cost‐effective and atom‐economical manner. In this context, very recently, Ohmiya's group realized a branch‐selective hydroacylation of styrenes 23‐2 with aromatic and aliphatic aldehydes 23‐1 using a quadruple NHC/cobalt/photo‐ redox/Brønsted base catalytic strategy (Scheme 23a) [35] . As a result, a large number of aryl‐alkyl ketones could be accessed with medium yields under visible light irradiation.…”

Section: Radical Acylation Of Alkenes Via Set Oxidation Of Nhc‐bound ...mentioning

confidence: 99%

“…In this context, very recently, Ohmiya's group realized a branch-selective hydroacylation of styrenes 23-2 with aromatic and aliphatic aldehydes 23-1 using a quadruple NHC/cobalt/photo-redox/ Brønsted base catalytic strategy (Scheme 23a). [35] As a result, a large number of aryl-alkyl ketones could be accessed with medium yields under visible light irradiation. In addition, the present protocol could also be applied in the late-stage functionalization of pharmaceutical molecules (Scheme 23b).…”

Section: Hydroacylation Of Alkenesmentioning

confidence: 99%

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Radical Acylation of Alkenes by NHC‐Organocatalysis

Tang,

Du,

Gao

2023

Eur J Org Chem

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N‐Heterocyclic carbene (NHC) catalyzed radical‐radical reactions have been proven to be powerful strategies for assembling ketyl‐containing compounds via single electron transfer (SET) pathway under either thermal conditions or photoredox conditions. In this context, acylation of alkenes via radical relay under NHC‐organocatalysis has also opened a new window for the difunctionalization of alkenes to construct valuable molecules in organic synthesis. In this review, the advances and progress of the acylation of alkenes via NHC‐organocatalysis were summarized according to different ways of generation of the key NHC‐bound ketyl‐type radicals. Furthermore, reaction scopes, limitations and mechanisms were discussed based on reaction types and catalytic systems. Conclusions and perspectives were also put forward at the end.

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Section: Radical Acylation Of Alkenes Via Set Oxidation Of Nhc‐bound ...mentioning

confidence: 99%

Section: Hydroacylation Of Alkenesmentioning

confidence: 99%

Radical Acylation of Alkenes by NHC‐Organocatalysis

Tang,

Du,

Gao

2023

Eur J Org Chem

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“…As an alternative, our proposed tactic relied on metal catalysed hydrogen atom transfer (MHAT) catalysis whereby a cobalt catalyst could selectively transfer a hydrogen atom to an unsaturated C−C bond [22–24] . We hypothesised that generation of this key cobalt hydride species under a photoinduced, reductive regime might allow us to pair this with reductive generation of a second radical, [25–29] ultimately leading to selective, sterically controlled coupling based on the persistent radical effect (Scheme 1c) [30] . For the heteroarene synthon, we sought to exploit pyridyl phosphonium salts, easy‐to‐synthesise precursors which have been extensively researched by McNally and co‐workers over the last years [31–36] .…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Cobalt Catalysis for the Reductive Coupling of Pyridines and Dienes Enabled by Paired Single‐Electron Transfer**

Qin,

Barday,

Jana

et al. 2023

Angew Chem Int Ed

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Selective hydroarylation of dienes has potential to provide swift access to useful building blocks. However, most existing methods rely on dienes stabilised by an aromatic group and transmetallation or nucleophilic attack steps require electron‐rich aryl coupling partners. As such, there are few examples which tolerate wide‐spread heteroarenes such as pyridine. Whilst allylic C–H functionalisation could be considered an alternative approach, the positional selectivity of unsymmetrical substrates is hard to control. Here, we report a general approach for selective hydropyridylation of dienes under mild conditions using metal catalysed hydrogen‐atom transfer. Photoinduced, reductive conditions enable simultaneous formation of a cobalt‐hydride catalyst and the persistent radical of easily‐synthesised pyridyl phosphonium salts. This facilitates selective coupling of dienes in a traceless manner at the C4‐position of a wide‐range of pyridine substrates. The mildness of the method is underscored by its functional group tolerance and demonstrated by applications in late‐stage‐functionalization. Based on a combination of experimental and computational studies, we propose a mechanistic pathway which proceeds through non‐reversible hydrogen atom transfer from a cobalt hydride species which is uniquely selective for dienes in the presence of other olefins due to a much higher relative barrier associated with olefin hydrogen‐atom‐transfer (HAT).

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“…Our group [37,38] and others [39][40][41][42][43][44][45][46] have recently exploited a reductive route to generating the key cobalt hydride, which performs hydrogen-atom transfer (HAT). This proceeds through sequential single-electron reduction of Co(II) to Co(I) and subsequent protonation.…”

mentioning

confidence: 99%

Dual‐Catalysed Intermolecular Reductive Coupling of Dienes and Ketones**

Mayerhofer,

Lippolis,

Teskey

2023

Angew Chem Int Ed

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We report a mild, catalytic method for the intermolecular reductive coupling of feedstock dienes and styrenes with ketones. Our conditions allow concomitant formation of a cobalt hydride species and single‐electron‐reduction of ketones. Subsequent selective hydrogen‐atom‐transfer from the cobalt hydride generates an allylic radical which can selectively couple with the persistent radical‐anion of the ketone. This radical‐radical coupling negates unfavourable steric interactions of ionic pathways and avoids the unstable alkoxy‐radical of previous radical olefin‐carbonyl couplings which were limited, as a result, to aldehydes. Applications of this novel and straightforward approach include the efficient synthesis of drug‐molecules, key‐intermediates in drug synthesis and site‐selective late‐stage functionalisation.

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Light-driven Radical-polar Crossover Catalysis Enabling Decarboxylative Fluorination of Redox Active Esters

Cited by 7 publications

References 36 publications

Radical Acylation of Alkenes by NHC‐Organocatalysis

Radical Acylation of Alkenes by NHC‐Organocatalysis

Photoinduced Cobalt Catalysis for the Reductive Coupling of Pyridines and Dienes Enabled by Paired Single‐Electron Transfer**

Dual‐Catalysed Intermolecular Reductive Coupling of Dienes and Ketones**

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