Synthetic Applications of Photocatalyzed Halogen‐Radical Mediated Hydrogen Atom Transfer for C−H Bond Functionalization

Bonciolini, Stefano; Noël, Timothy; Capaldo, Luca

doi:10.1002/ejoc.202200417

Cited by 64 publications

(54 citation statements)

References 131 publications

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“…6g , 27 , 28 In this scenario, the employed photocatalyst would oxidize the bromide generated upon oxidative addition to afford the halogen atom. 29 In fact, we found that the luminescence of the photocatalyst was quenched by TBABr and silane with comparable rates ( k SV = 325 and 121 M –1 , respectively). However, since the concentration of the latter is much higher, a direct photocatalyzed HAT is more likely.…”

Section: Resultsmentioning

confidence: 75%

The Merger of Benzophenone HAT Photocatalysis and Silyl Radical-Induced XAT Enables Both Nickel-Catalyzed Cross-Electrophile Coupling and 1,2-Dicarbofunctionalization of Olefins

et al. 2022

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A strategy for both cross-electrophile coupling and 1,2-dicarbofunctionalization of olefins has been developed. Carbon-centered radicals are generated from alkyl bromides by merging benzophenone hydrogen atom transfer (HAT) photocatalysis and silyl radical-induced halogen atom transfer (XAT) and are subsequently intercepted by a nickel catalyst to forge the targeted C(sp 3 )–C(sp 2 ) and C(sp 3 )–C(sp 3 ) bonds. The mild protocol is fast and scalable using flow technology, displays broad functional group tolerance, and is amenable to a wide variety of medicinally relevant moieties. Mechanistic investigations reveal that the ketone catalyst, upon photoexcitation, is responsible for the direct activation of the silicon-based XAT reagent (HAT-mediated XAT) that furnishes the targeted alkyl radical and is ultimately involved in the turnover of the nickel catalytic cycle.

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Section: Resultsmentioning

confidence: 75%

The Merger of Benzophenone HAT Photocatalysis and Silyl Radical-Induced XAT Enables Both Nickel-Catalyzed Cross-Electrophile Coupling and 1,2-Dicarbofunctionalization of Olefins

et al. 2022

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“…The sheer complexity of biologically active molecules demands continuous efforts from synthetic organic chemists to develop new and more efficient synthetic strategies . In addition, spurred by the principles of green chemistry and engineering, there is also a growing desire to develop greener and more sustainable processes. − With these boundary conditions in mind, it is only natural that photocatalysis has received significant attention from researchers in both academia and industry, providing benefits that include high selectivity, mild reaction conditions, improved safety, and the use of photons as green and traceless reagents. − …”

Section: Introductionmentioning

confidence: 99%

Rapid and Replaceable Luminescent Coating for Silicon-Based Microreactors Enabling Energy-Efficient Solar Photochemistry

Masson

Zondag

Debije

et al. 2022

ACS Sustainable Chem. Eng.

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The sun is the most sustainable source of photons on the earth but is rarely used in photochemical transformations due its relatively low and variable intensity, broad wavelength range, and lack of focus. Luminescent solar concentrator-based photomicroreactors (LSC-PMs) can be an answer to all these issues, but widespread adoption is plagued by challenges associated with their complicated manufacturing. Herein, we developed a new strategy to accelerate and ease the production of LSC-PMs by depositing a thin luminescent film on commercially and widely available silicon-based microreactors. The protocol is fast and operationally simple, and the luminescent coating can be easily removed and replaced. This enables rapid tuning of the luminescent coating to fit the requirements of the photocatalytic system and to increase the photon flux inside the microreactor channels.

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“…The possibility to exploit photonic energy in organic synthetic endeavors has dramatically impacted the way chemists assemble molecules. In particular, photocatalysis has enabled a convenient entry to open-shell intermediates, 1 spurring the development of efficient manifolds for the generation of C-, 2 N-3 and O-4 centered radicals, as well as halogen radicals, 5 which can be subsequently used to forge new chemical bonds. 6 In contrast, boron-based congeners have long remained in obscurity, 7 mainly due to the intrinsic difficulties associated with the handling of these highly electron-deficient and unstable intermediates.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Halogen-Atom Transfer (XAT) by N-heterocyclic carbene boryl radicals for C(sp3)−C(sp3) bond formation

Wan

Capaldo

Ravelli

et al. 2022

Preprint

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In the realm of radical chemistry, halogen-atom transfer (XAT) is emerging as a powerful activation strategy in synthetic endeavors to engage otherwise recalcitrant organic halides. Although toxic tin radicals have been in the spotlight as halo-gen abstractors for decades, the era of photocatalysis has brought to light more sustainable options. Herein, we present a comprehensive study on the use of ligated boryl radicals to enable C(sp3)−C(sp3) bond forming reactions via XAT from alkyl halides. Two strategies have been developed using either direct light activation with near UV or photoredox conditions with visible light; both pivoting on N-heterocyclic carbene (NHC) boryl radicals. The present XAT strategy is very mild and accommodates a broad scope of alkyl halides, including medicinally-relevant compounds and biologically-active molecules. The key role of NHC boryl radicals in the operative reaction mechanism has been elucidated through a combination of ex-perimental, spectroscopic and computational studies.

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Synthetic Applications of Photocatalyzed Halogen‐Radical Mediated Hydrogen Atom Transfer for C−H Bond Functionalization

Cited by 64 publications

References 131 publications

The Merger of Benzophenone HAT Photocatalysis and Silyl Radical-Induced XAT Enables Both Nickel-Catalyzed Cross-Electrophile Coupling and 1,2-Dicarbofunctionalization of Olefins

The Merger of Benzophenone HAT Photocatalysis and Silyl Radical-Induced XAT Enables Both Nickel-Catalyzed Cross-Electrophile Coupling and 1,2-Dicarbofunctionalization of Olefins

Rapid and Replaceable Luminescent Coating for Silicon-Based Microreactors Enabling Energy-Efficient Solar Photochemistry

Photoinduced Halogen-Atom Transfer (XAT) by N-heterocyclic carbene boryl radicals for C(sp3)−C(sp3) bond formation

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