Radical Hydrocarboxylation of Unactivated Alkenes via Photocatalytic Formate Activation

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(20), P. 10991 - 10997

Published: May 15, 2023

Herein we disclose a strategy to promote the hydrocarboxylation of unactivated alkenes using photochemical activation formate salts. We illustrate that an alternative initiation mechanism circumvents limitations prior approaches and enables this challenging substrate class. Specifically, found accessing requisite thiyl radical initiator without exogenous chromophore eliminates major byproducts have plagued attempts exploit similar reactivity for alkene substrates. This redox-neutral method is technically simple execute effective across broad range Feedstock alkenes, such as ethylene, are hydrocarboxylated at ambient temperature pressure. A series cyclization experiments indicate how described in report can be diverted by more complex processes.

Language: Английский

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Photo‐ and Electrochemical Cobalt Catalysed Hydrogen Atom Transfer for the Hydrofunctionalisation of Alkenes

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(41)

Published: May 15, 2023

Catalytic hydrogen atom transfer from metal-hydrides to alkenes allows feedstock olefins be used as alkyl radical precursors. The chemoselectivity of this process makes it an attractive synthetic tool and such has been regularly in synthesis complex molecules. However, onwards reactivity is limited by compatibility with the conditions which form key metal-hydride species. Now, through merger photocatalysis or electrochemistry, milder methods are emerging can unlock entirely new offer perspectives on expanding these unprecedented directions. This review outlines most recent developments electro- photochemical cobalt catalysed offers suggestions future outlook.

Language: Английский

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Organo‐Mediator Enabled Electrochemical Deuteration of Styrenes

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(45)

Published: Sept. 12, 2023

Despite widespread use of the deuterium isotope effect, selective labeling chemical molecules remains a major challenge. Herein, facile and general electrochemically driven, organic mediator enabled deuteration styrenes with oxide (D2 O) as economical source was reported. Importantly, this transformation could be suitable for various electron rich mediated by triphenylphosphine (TPP). The reaction proceeded under mild conditions without transition-metal catalysts, affording desired products in good yields excellent D-incorporation (D-inc, up to >99 %). Mechanistic investigations means experiments cyclic voltammetry tests provided sufficient support transformation. Notably, method proved powerful tool late-stage biorelevant compounds.

Language: Английский

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Electrochemically Driven Hydrogen Atom Transfer Catalysis: A Tool for C(sp³)/Si–H Functionalization and Hydrofunctionalization of Alkenes

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(13), P. 8731 - 8751

Published: June 16, 2023

Electrochemically driven hydrogen atom transfer (HAT) catalysis provides a complementary approach for the transformation of redox-inactive substrates that would be inaccessible to conventional electron (ET) catalysis. Moreover, electrochemically HAT could promote organic transformations with either abstraction or donation as key step. It versatile and effective tool direct functionalization C(sp3)–H/Si–H bonds hydrofunctionalization alkenes. Despite these attractive properties, has been largely overlooked due lack understanding both catalytic mechanism how catalyst selection should occur. In this Review, we give an overview applications in The mechanistic pathways, physical properties mediators, state-of-the-art examples are described discussed.

Language: Английский

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Carbon quaternization of redox active esters and olefins by decarboxylative coupling

Science, Journal Year: 2024, Volume and Issue: 384(6691), P. 113 - 118

Published: April 4, 2024

The synthesis of quaternary carbons often requires numerous steps and complex conditions or harsh reagents that act on heavily engineered substrates. This is largely a consequence conventional polar-bond retrosynthetic disconnections in turn require multiple functional group interconversions, redox manipulations, protecting chemistry. Here, we report simple catalyst reductant combination converts two types feedstock chemicals, carboxylic acids olefins, into tetrasubstituted through quaternization radical intermediates. An iron porphyrin activates each substrate by electron transfer hydrogen atom transfer, then combines the fragments using bimolecular homolytic substitution (S

Language: Английский

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Co-Catalyzed Hydrofluorination of Alkenes: Photocatalytic Method Development and Electroanalytical Mechanistic Investigation

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(7), P. 4380 - 4392

Published: Feb. 1, 2024

The hydrofluorination of alkenes represents an attractive strategy for the synthesis aliphatic fluorides. This approach provides a direct means to form C(sp3)–F bonds selectively from readily available alkenes. Nonetheless, conducting using nucleophilic fluorine sources poses significant challenges due low acidity and high toxicity associated with HF poor nucleophilicity fluoride. In this study, we present new Co(salen)-catalyzed simple utilizing Et3N·3HF as sole source both hydrogen fluorine. process operates via photoredox-mediated polar-radical-polar crossover mechanism. We also demonstrated versatility method by effectively converting diverse array activated varying degrees substitution into hydrofluorinated products. Furthermore, successfully applied methodology 18F-hydrofluorination reactions, enabling introduction 18F potential radiopharmaceuticals. Our mechanistic investigations, conducted rotating disk electrode voltammetry DFT calculations, unveiled involvement carbocation CoIV–alkyl species viable intermediates during fluorination step, contribution each pathway depends on structure starting alkene.

Language: Английский

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Photo‐ and Cobalt‐Catalyzed Synthesis of Heterocycles via Cycloisomerization of Unactivated Olefins

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(19)

Published: Feb. 28, 2024

Abstract We report a general, intramolecular cycloisomerization of unactivated olefins with pendant nucleophiles. The reaction proceeds under mild conditions and tolerates ethers, esters, protected amines, acetals, pyrazoles, carbamates, arenes. It is amenable to N ‐, O as well C ‐nucleophiles, yielding number different heterocycles including, but not limited to, pyrrolidines, piperidines, oxazolidinones, lactones. Use both benzothiazinoquinoxaline organophotocatalyst Co‐salen catalyst obviates the need for stoichiometric oxidant or reductant. showcase utility protocol in late‐stage drug diversification synthesis several small natural products.

Language: Английский

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Engaging Alkenes in Metallaphotoredox: A Triple Catalytic, Radical Sorting Approach to Olefin-Alcohol Cross-Coupling

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(18), P. 12300 - 12309

Published: April 24, 2024

Metallaphotoredox cross-coupling is a well-established strategy for generating clinically privileged aliphatic scaffolds via single-electron reactivity. Correspondingly, expanding metallaphotoredox to encompass new C(

Language: Английский

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Mechanism of Alkene Hydrofunctionalization by Oxidative Cobalt(salen) Catalyzed Hydrogen Atom Transfer

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(4), P. 2685 - 2700

Published: Jan. 16, 2024

Oxidative MHAT hydrofunctionalization of alkenes provides a mild cobalt-catalyzed route to forming C–N and C–O bonds. Here, we characterize relevant salen-supported cobalt complexes their reactions with alkenes, silanes, oxidant, solvent. These stoichiometric investigations are complemented by kinetic studies the catalytic reaction catalyst speciation. We describe solution characterization an elusive cobalt(III) fluoride complex, which surprisingly is not species that reacts silane under conditions; rather, aquo complex more active. Accordingly, addition water (0.15 M) speeds reaction, show enables product formation in 2 h at −50 °C acetone. Under these conditions, resting states can be observed UV–vis spectrophotometry, including cobalt(III)-alkyl complex. It comes from transient hydride formed turnover-limiting step cycle. This readily degrades but H2; it releases H+ through bimetallic pathway explains [Co]2 dependence off-cycle reaction. In contrast, rate follows power law kobs[Co]1[silane]1. Because different [Co] degradation lower loading improves yield reducing relative unproductive silane/oxidant consumption. illuminate mechanistic details oxidative lay groundwork for understanding other mediated alkyl complexes.

Language: Английский

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Light-Driven Cobalt Hydride Catalyzed Hydroarylation of Styrenes

ACS Catalysis, Journal Year: 2022, Volume and Issue: 12(24), P. 14806 - 14811

Published: Nov. 22, 2022

We report a conceptually distinct strategy for the synthesis of 1,1-diarylalkanes and triarylalkanes. Key to this approach is use light simultaneously trigger (i) formation CoIII–H species which undergoes H atom transfer (MHAT) styrenes, giving carbon-centered radical, (ii) generation persistent (hetero)arene radical. Selective coupling these two yields Markovnikov hydroarylation products under mild conditions without precious metals. In contrast many previous approaches, electron-deficient partners are favored it possible construct highly congested quaternary centers, including those with three different aryl groups.

Language: Английский

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