<i>N</i>‐Radical‐Initiated Cyclization through Insertion of Sulfur Dioxide under Photoinduced Catalyst‐Free Conditions

Mao, Runyu; Yuan, Zheng; Li, Yuewen; Wu, Jie

doi:10.1002/chem.201702040

Cited by 76 publications

(25 citation statements)

References 96 publications

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“…Second, generation of iminyl radicals from the electron‐poor O ‐aryl oximes via SET reduction was exploited by Loh and Xia (Scheme 1B) [5b,i] . Third, Leonori group and Wu group successively showcased that an electron donor‐acceptor complex (EDA), generated from the interaction of 2,4‐dinitro‐substituted aryl oximes with tertiary aliphatic amines, undergoes a SET/fragmentation process upon visible‐light excitation to access the iminyl radicals (Scheme 1C) [5j,n] . Fourth, Itoh and collaborators disclosed a novel and economical iminyl radical generation method mainly through hydrogen atom abstraction (HAT) of the excited photocatalyst 1‐chloroanthraquinone from benzyl oxime ethers (Scheme 1D) [5f] .…”

Section: Methodsmentioning

confidence: 99%

Photocatalytic Deoxygenative Carboimination towards Functionalized Pyrrolines by Using Unstrained γ,δ‐Unsaturated Oximes

Zhang

et al. 2021

Adv Synth Catal

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Photocatalytic deoxygenative carboimination of unstrained γ,δ‐unsaturated oximes with π‐acceptors including trifluoromethyl alkenes, 1‐trifluoromethyl‐1,3‐butadienes, gem‐difluoroalkenes, acrylates, and styrenes has been achieved which provides an efficient and mild approach to construct structurally diverse and highly functionalized pyrrolines with good functional group tolerance. Importantly, upon utilization of trifluoromethyl alkenes as the coupling partners, the developed protocol not only allows the introduction of the extremely valuable gem‐difluoroalkene functionality and pyrroline moiety into one molecule, but could also further transform the resulting gem‐difluoroalkene‐functionalized pyrrolines to the architecturally intriguing indolizine alkaloids via oxidation/reduction and sequential C−F bond cleavage. The mechanistic studies indicated that a free‐radical and anionic process was probably involved in this photocatalytic deoxygenative transformation.

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Section: Methodsmentioning

confidence: 99%

Photocatalytic Deoxygenative Carboimination towards Functionalized Pyrrolines by Using Unstrained γ,δ‐Unsaturated Oximes

Zhang

et al. 2021

Adv Synth Catal

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“…The catalyst‐free sulfonylative coupling of oxime esters 128 with silyl enolate 129 to obtain pyrrolines 130 was achieved using the combination of diazobicyclooctane‐SO 2 adduct (DABSO) and K 2 CO 3 (Scheme 48). [123] The authors postulated the formation of a photosensitive EDA complex of DABSO with 128 , which was confirmed by UV‐Vis spectroscopy. Presumably, one‐electron transfer occurs within the EDA complex with the formation of iminyl radical B that further undergoes intramolecular cyclization.…”

Section: Reactions Of Addition Of Oxime‐derived Iminyl Radicals To Multiple Carbon‐carbon Bondsmentioning

confidence: 89%

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

et al. 2021

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Oximes represent one of the fundamental organic compound classes with a wide range of synthetic applications. In the last decade O-substituted oximes were recognized as the synthetically available and versatile precursors of iminyl radicals via one-electron oxidation or one-electron reduction employing visible light photoredox catalysts, salts of abundant metals (such as Cu or Fe), or other convenient reagents. Iminyl radicals are powerful synthons for various processes of cyclization, ringopening, CH-functionalization, and coupling. The present review is focused on the synthetic methods based on oxime-derived iminyl radicals developed in the last few years excluding ring opening reactions of cyclic iminyl radicals that were summarized in recent publications. The review consists of two main parts:(1) reactions of iminyl radicals involving 1,n-hydrogen atom transfer (n = 5 in most cases) and (2) reactions involving the addition of iminyl radical to the carbon-carbon π-bond.

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“…[202] [203] Combing N-radical and SO 2 insertion chemistry, Wu's group discovered a N-radical-initiated cyclization through insertion of sulfur dioxide to give a variety of sulfonated 3,4-dihydro-2H-pyrroles with high efficiency and good selectivity under visible light irradiation (Scheme 68). [204] Furthermore, the corresponding 2-(3,4-dihydro-2H-pyrrol-2-yl) methylsulfonyl-1-arylethanones can be easily transformed into 3,4-dihydro-2H-1,4-thiazine 1,1-dioxides. This process occurs efficiently at room temperature without the requirement of any photocatalysts, and various functional groups can be tolerated.…”

Section: Radical Cyclizations Through Nitrogen-centered Radicalsmentioning

confidence: 99%

Progress in Photoinduced Radical Reactions using Electron Donor‐Acceptor Complexes

et al. 2021

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Photocatalyzed organic synthesis transformation is a remarkable green synthetic strategy because of the advantages of operational simplicity, high chemoselectivities, cheap, and environmental benignancy, along with the extensive applications in the fields of organic, pharmaceutical and functional material chemistry. Generally, photoredox catalysts or photosensitizers are necessary for the generation of their excited states to perform the successive oxidative or reductive reactions through the single electron transfer (SET) or energy transfer (ET) process. Furthermore, the exploration of a colored electron donor-acceptor (EDA) complex or a charge transfer (CT) complex between an electron-rich and an electron-poor substrate provides the chance to deliver the excited intermediate under the irradiation of light, resulting in the formation of radical activate species through a single electron transfer to induce successive various radical reactions. These reactions were performed without the need of any external photocatalysts under mild reaction conditions. Herein, this review focuses on the recent progress on photoinduced radical addition reactions, radical borylations, reductive reactions, radical-radical cross-coupling reactions, degradation reactions and radical cascade cyclization via EDA complexes. We highlight these novel green synthetic methodologies and applications, as well as the mechanisms. This review will help to provide references for organic and medicinal chemists who are charmed by these green organic photochemical transformations based on EDA complexes.

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N‐Radical‐Initiated Cyclization through Insertion of Sulfur Dioxide under Photoinduced Catalyst‐Free Conditions

Cited by 76 publications

References 96 publications

Photocatalytic Deoxygenative Carboimination towards Functionalized Pyrrolines by Using Unstrained γ,δ‐Unsaturated Oximes

Photocatalytic Deoxygenative Carboimination towards Functionalized Pyrrolines by Using Unstrained γ,δ‐Unsaturated Oximes

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

Progress in Photoinduced Radical Reactions using Electron Donor‐Acceptor Complexes

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