Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration of aliphatic C-H bonds. In this manifold, a photocatalyst (PCHAT) exploits the energy of a photon to trigger the homolytic cleavage of such bonds in organic compounds. Selective C-H bond elaboration may be achieved by a judicious choice of the hydrogen abstractor (key parameters are the electronic character and the molecular structure), as well as reaction additives. Different are the classes of PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin and a tris(amino)cyclopropenium radical dication. The processes (mainly C-C bond formation) are in most cases carried out under mild conditions with the help of visible light. The aim of this review is to offer a comprehensive survey of the synthetic applications of photocatalyzed d-HAT.

Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C-H Bonds Elaboration

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.

Photoredox-Catalyzed C-H Functionalization Reactions.

In recent years, visible light-induced transition metal catalysis has emerged as a new paradigm in organic photocatalysis, which has led to the discovery of unprecedented transformations as well as the improvement of known reactions. In this subfield of photocatalysis, a transition metal complex serves a double duty by harvesting photon energy and then enabling bond forming/breaking events mostly via a single catalytic cycle, thus contrasting the established dual photocatalysis in which an exogenous photosensitizer is employed. In addition, this approach often synergistically combines catalyst-substrate interaction with photoinduced process, a feature that is uncommon in conventional photoredox chemistry. This Review describes the early development and recent advances of this emerging field.

Visible Light-Induced Transition Metal Catalysis.

Summary Hydrogen-atom transfer (HAT) provides straightforward methods to generate open-shell radical intermediates from R-H (R = C, Si, etc.) bonds and offers unique opportunities for green and sustainable synthesis. Traditional HAT protocols required harsh conditions and relied on the use of harmful reagents such as Cl2 and peroxides. An emerging strategy is photoinduced intermolecular HAT, in which transformations can be driven by photocatalysis under mild conditions. In recent years, photoinduced intermolecular HAT reactions have seen substantial development of their versatility, efficiency, and selectivity. This review summarizes recent advances (up to December 2020) in this rapidly expanding research area. The representative examples provided are classified according to the active species responsible for hydrogen atom abstraction. The reactivity, selectivity, and established transformations for each type of active species are briefly summarized. This review aims to provide guidance for the application of photoinduced HAT in R-H functionalization reactions and to inspire further progress in this research area.

Photoinduced intermolecular hydrogen atom transfer reactions in organic synthesis

Abstract A mild and selective C(sp3)−H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C−H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (−)‐ambroxide, pregnenolone acetate, (+)‐sclareolide, and artemisinin, exemplifies the utility of this new method.

Selective sp3 C–H aerobic oxidation enabled by decatungstate photocatalysis in flow

In the presence of tetrabutylammonium decatungstate and chiral spiro phosphoric acid, a light-mediated asymmetric C–H functionalization of unactivated hydrocarbons with exocyclic enones has been es...

Light-Mediated Asymmetric Aliphatic C–H Alkylation with Hydrogen Atom Transfer Catalyst and Chiral Phosphoric Acid

Asymmetric Photocatalytic C(sp3)–H Bond Addition to α-Substituted Acrylates

Enantioselective functionalization of alkenes is an attractive and straightforward method to assemble molecular complexity from readily available chemical feedstocks. Although regio- and enantioselective transformations of the C=C bond of alkenes have been extensively studied, those of the allylic C–H bonds of unactivated alkenes are yet to be explored. Here we report a palladium-catalysed branch- and enantioselective allylic C–H alkylation that is capable of accommodating diverse types of α-alkenes, ranging from feedstocks annually manufactured on a million-tonne scale to olefins tethering a wide scope of appended functionalities, providing unconventional access to chiral γ,δ-unsaturated amides. Notably, mechanistic studies reveal that regioselectivity is not only governed by the coordination pattern of nucleophiles but also regulated by the ligational behaviours of ligands, highlighting the importance of the monoligation of chiral phosphoramidite ligands in provoking high levels of stereo- and branch-selectivity via a nucleophile coordination-enabled inner-sphere allylation pathway. The selective functionalization of C=C bonds of alkenes is well studied, however, regio- and enantioselective transformations of the allylic C–H bond of unactivated alkenes are relatively underexplored. Now, a palladium-catalysed branch-selective and enantioselective allylic C−H alkylation of α-alkenes is reported. The process tolerates a wide range of α-alkenes, from chemical feedstocks to bioactive α-alkenes 

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Palladium-catalysed branch- and enantioselective allylic C–H alkylation of α-alkenes

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Palladium-Catalyzed Enantioselective C(sp3)–H/C(sp3)–H Umpolung Coupling of N-Allylimine and α-Aryl Ketones”Tian-Ci WangTian-Ci WangMore by Tian-Ci Wang, Ling ZhuLing ZhuMore by Ling Zhu, Shiwei LuoShiwei LuoMore by Shiwei Luo, Zhong-Sheng NongZhong-Sheng NongMore by Zhong-Sheng Nong, Pu-Sheng Wang*Pu-Sheng WangMore by Pu-Sheng Wanghttps://orcid.org/0000-0002-7229-3426, and Liu-Zhu Gong*Liu-Zhu GongMore by Liu-Zhu Gonghttps://orcid.org/0000-0001-6099-827XCite this: J. Am. Chem. Soc. 2022, 144, 40, 18710Publication Date (Web):October 3, 2022Publication History Received9 August 2022Published online3 October 2022Published inissue 12 October 2022https://doi.org/10.1021/jacs.2c08467Copyright © 2022 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1890Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (806 KB) Get e-Alerts Get e-Alerts 

Zhong-Sheng Nong

Papers

Light-Mediated Asymmetric Aliphatic C–H Alkylation with Hydrogen Atom Transfer Catalyst and Chiral Phosphoric Acid

Asymmetric Photocatalytic C(sp3)–H Bond Addition to α-Substituted Acrylates

Palladium-catalysed branch- and enantioselective allylic C–H alkylation of α-alkenes

Correction to "Palladium-Catalyzed Enantioselective C(sp3)-H/C(sp3)-H Umpolung Coupling of N-Allylimine and α-Aryl Ketones".