The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Aiwen Lei - One of the best experts on this subject based on the ideXlab platform.
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Photocatalytic Dehydrogenative Cross‐Coupling of Alkenes with Alcohols or Azoles without External Oxidant
Angewandte Chemie (International ed. in English), 2016Co-Authors: Linbin Niu, Chunlan Song, Bowen Dou, Atul K. Singh, Aiwen LeiAbstract:Direct cross-coupling between alkenes/R-H or alkenes/RXH is a dream reaction, especially without external oxidants. Inputting energy by photocatalysis and employing a cobalt catalyst as a two-electron acceptor, a direct C−H/X−H cross-coupling with H2 evolution has been achieved for C−O and C−N bond formation. A new Radical Alkenylation using alkene as the redox compound is presented. A wide range of aliphatic alcohols—even long chain alcohols—are tolerated well in this system, providing a new route to multi-substituted enol ether derivatives using simple alkenes. Additionally, this protocol can also be used for N-vinylazole synthesis. Mechanistic insights reveal that the cobalt catalyst oxidizes the photocatalyst to revive the photocatalytic cycle.
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Olefinic C–H functionalization through Radical Alkenylation
Chemical Society reviews, 2015Co-Authors: Shan Tang, Kun Liu, Chao Liu, Aiwen LeiAbstract:Direct olefinic C–H functionalization represents the ideal way of introducing an alkenyl group into organic molecules. A well-known process is the Heck reaction, which involves alkene insertion and β-hydride elimination in the presence of a transition metal. However, the traditional Heck reaction mainly deals with the Alkenylation of aryl or vinyl electrophiles. Recent developments have revealed that Alkenylation can also be achieved through Radical addition to alkenes and following single-electron-transfer (SET) oxidation/elimination. The Radical Alkenylation pathway allows Alkenylation with a variety of carbon-centered Radicals and even heteroatom-centered Radicals. This tutorial review gives an overview of recent advances in this emerging field.
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olefinic c h functionalization through Radical Alkenylation
Chemical Society Reviews, 2015Co-Authors: Shan Tang, Aiwen Lei, Kun Liu, Chao LiuAbstract:Direct olefinic C–H functionalization represents the ideal way of introducing an alkenyl group into organic molecules. A well-known process is the Heck reaction, which involves alkene insertion and β-hydride elimination in the presence of a transition metal. However, the traditional Heck reaction mainly deals with the Alkenylation of aryl or vinyl electrophiles. Recent developments have revealed that Alkenylation can also be achieved through Radical addition to alkenes and following single-electron-transfer (SET) oxidation/elimination. The Radical Alkenylation pathway allows Alkenylation with a variety of carbon-centered Radicals and even heteroatom-centered Radicals. This tutorial review gives an overview of recent advances in this emerging field.
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Copper-catalysed direct Radical Alkenylation of alkyl bromides
Organic & biomolecular chemistry, 2014Co-Authors: Xu Zhang, Zhixiong Liao, Guoting Zhang, Chao Fan, Chu Qin, Jie Liu, Aiwen LeiAbstract:A copper-catalysed direct Radical Alkenylation of various benzyl bromides and α-carbonyl alkyl bromides has been developed. Compared with the recent Radical Alkenylations which mostly focused on secondary or tertiary alkyl halides, this transformation shows good reactivity to primary alkyl halides and tertiary, secondary alkyl halides were also tolerated. The key initiation step of this transformation is a copper-induced single-electron reduction of C–Br bonds to generate alkyl Radical species.
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revealing the metal like behavior of iodine an iodide catalysed Radical oxidative Alkenylation
Chemical Communications, 2014Co-Authors: Shan Tang, Aiwen Lei, Chao Liu, Wenqing Liao, Ruopeng BaiAbstract:In this work, we have described an alternative Alkenylation approach to illustrate the metal-like behaviour of iodine in cross-coupling reactions. Alkenylation could proceed through iodide catalysed Radical initiation, Radical addition and iodine promoted alkenyl functionality recovery. Catalytic HI elimination similar to the β-hydride elimination of transition metals was realized for the Radical Alkenylation of sulfonyl hydrazides. Operando IR and cyclic voltammetry experiments were carried out to confirm the crucial role of iodine in the Radical Alkenylation process.
Ilhyong Ryu - One of the best experts on this subject based on the ideXlab platform.
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Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones
Organic letters, 2018Co-Authors: Shuhei Sumino, Misae Uno, Hsin-ju Huang, Ilhyong RyuAbstract:Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/photoirradiation system. The initial alkyl Radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO2PdI, which is formed by the combination of the sulfonyl Radical and the palladium Radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO2I.
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palladium light induced Radical Alkenylation and allylation of alkyl iodides using alkenyl and allylic sulfones
Organic Letters, 2018Co-Authors: Shuhei Sumino, Misae Uno, Hsin-ju Huang, Ilhyong RyuAbstract:Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/photoirradiation system. The initial alkyl Radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO2PdI, which is formed by the combination of the sulfonyl Radical and the palladium Radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO2I.
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Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones
2018Co-Authors: Shuhei Sumino, Misae Uno, Hsin-ju Huang, Ilhyong RyuAbstract:Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/photoirradiation system. The initial alkyl Radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO2PdI, which is formed by the combination of the sulfonyl Radical and the palladium Radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO2I
Xu Zhang - One of the best experts on this subject based on the ideXlab platform.
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Copper-catalysed direct Radical Alkenylation of alkyl bromides
Organic & biomolecular chemistry, 2014Co-Authors: Xu Zhang, Zhixiong Liao, Guoting Zhang, Chao Fan, Chu Qin, Jie Liu, Aiwen LeiAbstract:A copper-catalysed direct Radical Alkenylation of various benzyl bromides and α-carbonyl alkyl bromides has been developed. Compared with the recent Radical Alkenylations which mostly focused on secondary or tertiary alkyl halides, this transformation shows good reactivity to primary alkyl halides and tertiary, secondary alkyl halides were also tolerated. The key initiation step of this transformation is a copper-induced single-electron reduction of C–Br bonds to generate alkyl Radical species.
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visible light photocatalytic Radical Alkenylation of α carbonyl alkyl bromides and benzyl bromides
ChemInform, 2013Co-Authors: Qiang Liu, Xu Zhang, Jie Liu, Yuhong Yang, Ziqi Zeng, Aiwen LeiAbstract:The process is optimized with conditions A) or B) in the presence of either a Ru or an Ir polypyridyl complex.
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visible light photocatalytic Radical Alkenylation of α carbonyl alkyl bromides and benzyl bromides
Chemistry: A European Journal, 2013Co-Authors: Qiang Liu, Xu Zhang, Jie Liu, Aiwen Lei, Yuhong Yang, Ziqi ZengAbstract:Through the use of [Ru(bpy)3Cl2] (bpy=2,2'-bipyridine) and [Ir(ppy)3] (ppy=phenylpyridine) as photocatalysts, we have achieved the first example of visible-light photocatalytic Radical Alkenylation of various α-carbonyl alkyl bromides and benzyl bromides to furnish α-vinyl carbonyls and allylbenzene derivatives, prominent structural elements of many bioactive molecules. Specifically, this transformation is regiospecific and can tolerate primary, secondary, and even tertiary alkyl halides that bear β-hydrides, which can be challenging with traditional palladium-catalyzed approaches. The key initiation step of this transformation is visible-light-induced single-electron reduction of C-Br bonds to generate alkyl Radical species promoted by photocatalysts. The following carbon-carbon bond-forming step involves a Radical addition step rather than a metal-mediated process, thereby avoiding the undesired β-hydride elimination side reaction. Moreover, we propose that the Ru and Ir photocatalysts play a dual role in the catalytic system: they absorb energy from the visible light to facilitate the reaction process and act as a medium of electron transfer to activate the alkyl halides more effectively. Overall, this photoredox catalysis method opens new synthetic opportunities for the efficient Alkenylation of alkyl halides that contain β-hydrides under mild conditions.
Koichiro Oshima - One of the best experts on this subject based on the ideXlab platform.
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Cobalt-Catalyzed Trimethylsilylmethylmagnesium-Promoted Radical Alkenylation of Alkyl Halides: A Complement to the Heck Reaction
Journal of the American Chemical Society, 2006Co-Authors: Walter Affo, Hideki Yorimitsu, Koichiro Oshima, Hirohisa Ohmiya, Takuma Fujioka, Yousuke Ikeda, Tomoaki Nakamura, Yuki Imamura, Tsutomu Mizuta, Katsuhiko MiyoshiAbstract:A cobalt complex, [CoCl2(dpph)] (DPPH = [1,6-bis(diphenylphosphino)hexane]), catalyzes an intermolecular styrylation reaction of alkyl halides in the presence of Me3SiCH2MgCl in ether to yield β-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can participate in the styrylation. A Radical mechanism is strongly suggested for the styrylation reaction. The sequential isomerization/styrylation reactions of cyclopropylmethyl bromide and 6-bromo-1-hexene provide evidence of the Radical mechanism. Crystallographic and spectroscopic investigations on cobalt complexes reveal that the reaction would begin with single electron transfer from an electron-rich (diphosphine)bis(trimethylsilylmethyl)cobalt(II) complex followed by reductive elimination to yield 1,2-bis(trimethylsilyl)ethane and a (diphosphine)cobalt(I) complex. The combination of [CoCl2(dppb)] (DPPB = [1,4-bis(diphenylphosphino)butane]) catalyst and Me3SiCH2MgCl induces intramolecular Heck-type cyclization reactions of 6-halo-1-hexenes ...
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Radical allylation, vinylation, alkynylation, and phenylation reactions of α-halo carbonyl compounds with organoboron, organogallium, and organoindium reagents
Synthesis, 2005Co-Authors: Kazuaki Takami, Hideki Yorimitsu, Shin‐ichi Usugi, Koichiro OshimaAbstract:Allylic gallium and indium reagents are found to mediate Radical allylation reactions of α-iodo or α-bromo carbonyl compounds. Treatment of benzyl bromoacetate with allylgallium, prepared from allylmagnesium chloride and gallium trichloride, in the presence of triethylborane provided benzyl 4-pentenoate in excellent yield. Addition of water as a co-solvent improved the yields of allylated products. Allylic indium reagents are also useful and can replace the gallium reagents. A diallylborane reagent can allylate an α-iodo ester in good yield. Alkenylation reactions of α-halo carbonyl compounds with alkenylindium proceeded via a Radical process in the presence of triethylborane. Unactivated alkene moieties and styryl groups were introduced by this method. The carbon-carbon double bond geometry of the alkenylindiums was retained during the Alkenylation. Preparation of an alkenylindium via a hydroindation of 1-alkyne and subsequent Radical Alkenylation established an efficient one-pot strategy. Radical alkynylations and phenylations with organoindium reagents are disclosed herein.
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Radical Alkenylation of alpha-halo carbonyl compounds with alkenylindiums.
Organic letters, 2004Co-Authors: Kazuaki Takami, Hideki Yorimitsu, Koichiro OshimaAbstract:Alkenylation reaction of alpha-halo carbonyl compounds with alkenylindiums proceeded via a Radical process in the presence of triethylborane. Unactivated alkene moieties as well as a styryl group could be introduced by this method. The geometry of the carbon-carbon double bonds of the alkenylindiums was retained. Preparation of an alkenylindium via a hydroindation of 1-alkyne followed by Radical Alkenylation established an efficient one-pot strategy. [reaction: see text]
Jie Liu - One of the best experts on this subject based on the ideXlab platform.
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Copper-catalysed direct Radical Alkenylation of alkyl bromides
Organic & biomolecular chemistry, 2014Co-Authors: Xu Zhang, Zhixiong Liao, Guoting Zhang, Chao Fan, Chu Qin, Jie Liu, Aiwen LeiAbstract:A copper-catalysed direct Radical Alkenylation of various benzyl bromides and α-carbonyl alkyl bromides has been developed. Compared with the recent Radical Alkenylations which mostly focused on secondary or tertiary alkyl halides, this transformation shows good reactivity to primary alkyl halides and tertiary, secondary alkyl halides were also tolerated. The key initiation step of this transformation is a copper-induced single-electron reduction of C–Br bonds to generate alkyl Radical species.
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visible light photocatalytic Radical Alkenylation of α carbonyl alkyl bromides and benzyl bromides
ChemInform, 2013Co-Authors: Qiang Liu, Xu Zhang, Jie Liu, Yuhong Yang, Ziqi Zeng, Aiwen LeiAbstract:The process is optimized with conditions A) or B) in the presence of either a Ru or an Ir polypyridyl complex.
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visible light photocatalytic Radical Alkenylation of α carbonyl alkyl bromides and benzyl bromides
Chemistry: A European Journal, 2013Co-Authors: Qiang Liu, Xu Zhang, Jie Liu, Aiwen Lei, Yuhong Yang, Ziqi ZengAbstract:Through the use of [Ru(bpy)3Cl2] (bpy=2,2'-bipyridine) and [Ir(ppy)3] (ppy=phenylpyridine) as photocatalysts, we have achieved the first example of visible-light photocatalytic Radical Alkenylation of various α-carbonyl alkyl bromides and benzyl bromides to furnish α-vinyl carbonyls and allylbenzene derivatives, prominent structural elements of many bioactive molecules. Specifically, this transformation is regiospecific and can tolerate primary, secondary, and even tertiary alkyl halides that bear β-hydrides, which can be challenging with traditional palladium-catalyzed approaches. The key initiation step of this transformation is visible-light-induced single-electron reduction of C-Br bonds to generate alkyl Radical species promoted by photocatalysts. The following carbon-carbon bond-forming step involves a Radical addition step rather than a metal-mediated process, thereby avoiding the undesired β-hydride elimination side reaction. Moreover, we propose that the Ru and Ir photocatalysts play a dual role in the catalytic system: they absorb energy from the visible light to facilitate the reaction process and act as a medium of electron transfer to activate the alkyl halides more effectively. Overall, this photoredox catalysis method opens new synthetic opportunities for the efficient Alkenylation of alkyl halides that contain β-hydrides under mild conditions.
