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Arturo Espinosa Ferao - One of the best experts on this subject based on the ideXlab platform.
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on the mechanism of trimethylphosphine mediated Reductive Dimerization of ketones
Inorganic Chemistry, 2018Co-Authors: Arturo Espinosa FeraoAbstract:High-level single-reference calculations reveal that trimethylphosphine-mediated Reductive Dimerization of properly substituted (e.g., CF3) ketones proceeds via initial formation of an oxaphosphirane intermediate, with the oxygen atom occupying an equatorial position at phosphorus. In the “oxirane route”, this oxaphosphirane intermediate loses a trimethylphosphine oxide unit, thus behaving as a carbene transfer agent toward a second carbonyl molecule and giving rise to a carbonyl ylide that cyclizates to the corresponding oxirane. This in turn transfers the carbene unit to a second phosphine molecule, with loss of acetone, affording a phosphorane. The latter undergoes typical Wittig reaction to the final homocoupling product through the oxaphosphetane intermediate. The alternative direct conversion of oxaphosphirane into phosphorane constitutes the lowest energy path as it skips the highest barrier oxirane → phosphorane conversion. The oxirane route is favored by the use of polar solvents and electron def...
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On the Mechanism of Trimethylphosphine-Mediated Reductive Dimerization of Ketones
2018Co-Authors: Arturo Espinosa FeraoAbstract:High-level single-reference calculations reveal that trimethylphosphine-mediated Reductive Dimerization of properly substituted (e.g., CF3) ketones proceeds via initial formation of an oxaphosphirane intermediate, with the oxygen atom occupying an equatorial position at phosphorus. In the “oxirane route”, this oxaphosphirane intermediate loses a trimethylphosphine oxide unit, thus behaving as a carbene transfer agent toward a second carbonyl molecule and giving rise to a carbonyl ylide that cyclizates to the corresponding oxirane. This in turn transfers the carbene unit to a second phosphine molecule, with loss of acetone, affording a phosphorane. The latter undergoes typical Wittig reaction to the final homocoupling product through the oxaphosphetane intermediate. The alternative direct conversion of oxaphosphirane into phosphorane constitutes the lowest energy path as it skips the highest barrier oxirane → phosphorane conversion. The oxirane route is favored by the use of polar solvents and electron deficient carbonyl components. The lowest barrier most exergonic process from oxaphosphirane is the pericyclic cycloaddition of the acetone CO bond along the endocyclic P–C bond, furnishing the stable 1,3,2-dioxaphospholane product
Yongmin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Zinc-mediated Reductive Dimerization Cyclization of Ethyl Arylmethylidene cyanoacetates in Aqueous Media
Journal of Chemical Research, 1999Co-Authors: Lei Wang, Yongmin ZhangAbstract:Zinc-mediated Reductive Dimerization–cyclization of ethyl arylmethylidenecyanoacetates occurs to give diethyl 2-amino-3-cyano-4,5-diaryl-1,3-cyclopentenedicarboxylates in moderate to good yields the trans, trans-form isomer being the major product.
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Metallic samarium promoted Reductive Dimerization cyclization of gem-diactivated alkenes, Reductive debromination of vic-dibromides, and reduction of sodium alkyl thiosulfates in aqueous media
Tetrahedron, 1999Co-Authors: Lei Wang, Yongmin ZhangAbstract:Abstract In saturated NH 4 Cl (ap.)-THF solution at room temperature, metallic samarium promoted Reductive Dimerization cyclization of gem -diactivated alkenes, Reductive debromination of vic -dibromides, and reduction of sodium alkyl thiosulfates occur to afford corresponding functionalized cyclopentenes, ( E )-alkenes, and disulfides, respectively in good yield. Only sub-stoichiometric quantities of samarium are employed in the former reactions and the trans - or trans,trans -form isomer is the majority product of the polysubstituted cyclopentene products.
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Novel Reductive Dimerization Cyclization of 1,1-Dicyanoalkenes Mediated by Zinc in Aqueous Media
Synthetic Communications, 1998Co-Authors: Lei Wang, Yongmin ZhangAbstract:Abstract Zinc-mediated Reductive Dimerization cyclization of 1,1-dicyanoalkenes 1 occurs to give functionalized cyclopentenes 2(cis) and 3(trans) in good yields under saturated aqueous NH4Cl-THF solution at room temperature. 3 is major product.
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Water accelerated reduction system: Pinacolic coupling of aromatic carbonyl compounds and Reductive Dimerization cyclization of 1,1-dicyanoalkenes
Tetrahedron, 1998Co-Authors: Lei Wang, Yongmin ZhangAbstract:Abstract By action of Sm TMSCl in THF at room temperature, aromatic carbonyl compounds produce the corresponding 1,2-diols via Reductive coupling reaction and 1,1-dicyanoalkenes produce the functionalized cyclopentenes through Reductive Dimerization followed by intramolecular cyclization in one-pot. The former gives approximately equal amounts of ( dl )- and ( meso )-1,2-diols and the later gives the major trans -form products. Added micro amounts of water to the system not only can accelerate the reaction, but also increase the yields of products. Moreover, only substoichiometric quantities of metallic samarium are employed.
Lei Wang - One of the best experts on this subject based on the ideXlab platform.
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Zinc-mediated Reductive Dimerization Cyclization of Ethyl Arylmethylidene cyanoacetates in Aqueous Media
Journal of Chemical Research, 1999Co-Authors: Lei Wang, Yongmin ZhangAbstract:Zinc-mediated Reductive Dimerization–cyclization of ethyl arylmethylidenecyanoacetates occurs to give diethyl 2-amino-3-cyano-4,5-diaryl-1,3-cyclopentenedicarboxylates in moderate to good yields the trans, trans-form isomer being the major product.
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Metallic samarium promoted Reductive Dimerization cyclization of gem-diactivated alkenes, Reductive debromination of vic-dibromides, and reduction of sodium alkyl thiosulfates in aqueous media
Tetrahedron, 1999Co-Authors: Lei Wang, Yongmin ZhangAbstract:Abstract In saturated NH 4 Cl (ap.)-THF solution at room temperature, metallic samarium promoted Reductive Dimerization cyclization of gem -diactivated alkenes, Reductive debromination of vic -dibromides, and reduction of sodium alkyl thiosulfates occur to afford corresponding functionalized cyclopentenes, ( E )-alkenes, and disulfides, respectively in good yield. Only sub-stoichiometric quantities of samarium are employed in the former reactions and the trans - or trans,trans -form isomer is the majority product of the polysubstituted cyclopentene products.
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Novel Reductive Dimerization Cyclization of 1,1-Dicyanoalkenes Mediated by Zinc in Aqueous Media
Synthetic Communications, 1998Co-Authors: Lei Wang, Yongmin ZhangAbstract:Abstract Zinc-mediated Reductive Dimerization cyclization of 1,1-dicyanoalkenes 1 occurs to give functionalized cyclopentenes 2(cis) and 3(trans) in good yields under saturated aqueous NH4Cl-THF solution at room temperature. 3 is major product.
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Water accelerated reduction system: Pinacolic coupling of aromatic carbonyl compounds and Reductive Dimerization cyclization of 1,1-dicyanoalkenes
Tetrahedron, 1998Co-Authors: Lei Wang, Yongmin ZhangAbstract:Abstract By action of Sm TMSCl in THF at room temperature, aromatic carbonyl compounds produce the corresponding 1,2-diols via Reductive coupling reaction and 1,1-dicyanoalkenes produce the functionalized cyclopentenes through Reductive Dimerization followed by intramolecular cyclization in one-pot. The former gives approximately equal amounts of ( dl )- and ( meso )-1,2-diols and the later gives the major trans -form products. Added micro amounts of water to the system not only can accelerate the reaction, but also increase the yields of products. Moreover, only substoichiometric quantities of metallic samarium are employed.
Yuzo Fujiwara - One of the best experts on this subject based on the ideXlab platform.
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a novel Reductive Dimerization oxidative dehydrogenation of aldimines mediated by lanthanoid metals
Journal of Organic Chemistry, 2001Co-Authors: Wusong Jin, Yoshikazu Makioka, Tsugio Kitamura, Yuzo FujiwaraAbstract:A lanthanoid metal-mediated novel Reductive Dimerization/oxidative dehydrogenation of a variety of aldimines has been achieved. Aromatic aldimines (1) were dimerized in the presence of 0.5 mol of ytterbium metal (Yb) and 1-naphthaldehyde (1-NpCHO) to give the corresponding vicinal diimines (2) in good to high yields. Samarium metal (Sm) or samarium(II) diiodide (SmI2) gives unsatisfied yields under the same reaction conditions. As an oxidant, 1-NpCHO gives the best result. In addition, HMPA plays an important role as a cosolvent in this reaction. Reaction of various aldimines with Yb metal is disscussed in detail. Moreover, it has been found that the electron-donating substitutents on the benzene ring promote the reaction and that the electron-withdrawing substitutents retard the reaction. The reaction of deuterated N-benzylideneaniline with Yb metal confirmed that transformation of the hydride occurred from aldimines to the oxidant aldehyde. The mechanism of the reaction was discussed.
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A novel Reductive Dimerization/oxidative dehydrogenation of aldimines mediated by lanthanoid metals.
The Journal of Organic Chemistry, 2001Co-Authors: Wusong Jin, Yoshikazu Makioka, Tsugio Kitamura, Yuzo FujiwaraAbstract:A lanthanoid metal-mediated novel Reductive Dimerization/oxidative dehydrogenation of a variety of aldimines has been achieved. Aromatic aldimines (1) were dimerized in the presence of 0.5 mol of ytterbium metal (Yb) and 1-naphthaldehyde (1-NpCHO) to give the corresponding vicinal diimines (2) in good to high yields. Samarium metal (Sm) or samarium(II) diiodide (SmI2) gives unsatisfied yields under the same reaction conditions. As an oxidant, 1-NpCHO gives the best result. In addition, HMPA plays an important role as a cosolvent in this reaction. Reaction of various aldimines with Yb metal is disscussed in detail. Moreover, it has been found that the electron-donating substitutents on the benzene ring promote the reaction and that the electron-withdrawing substitutents retard the reaction. The reaction of deuterated N-benzylideneaniline with Yb metal confirmed that transformation of the hydride occurred from aldimines to the oxidant aldehyde. The mechanism of the reaction was discussed.
Zhu-jun Yao - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of 2,3-Dialkylated Tartaric Acid Esters via Visible Light Photoredox-Catalyzed Reductive Dimerization of α-Ketoesters
ACS Omega, 2017Co-Authors: Jing Zhu, Yi Yuan, Shaozhong Wang, Zhu-jun YaoAbstract:A mild transition-metal-free protocol to prepare 2,3-dialkylated tartaric acid esters has been developed by taking advantage of a visible light photoredox-catalyzed Reductive Dimerization of α-ketoesters with a combination of an organic dye photocatalyst and a Hantzsch-type 1,4-dihydropyridine hydrogen donor. A broad range of functional groups including cyclopropane, alkene, alkyne, 4-methoxybenzyl ether, acetal, silyl ether, carbamate, cyclic ether, cyclic thioether, bromoalkane, and N-alkoxyphthalimide are well-compatible. By employing the visible light photoredox-catalyzed Reductive coupling and the subsequent optical resolution, both enantioenriched diastereomers of 2,3-dialkylated tartaric acid could be acquired conveniently.
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Synthesis of 2,3-Dialkylated Tartaric Acid Esters via Visible Light Photoredox-Catalyzed Reductive Dimerization of α‑Ketoesters
2017Co-Authors: Jing Zhu, Yi Yuan, Shaozhong Wang, Zhu-jun YaoAbstract:A mild transition-metal-free protocol to prepare 2,3-dialkylated tartaric acid esters has been developed by taking advantage of a visible light photoredox-catalyzed Reductive Dimerization of α-ketoesters with a combination of an organic dye photocatalyst and a Hantzsch-type 1,4-dihydropyridine hydrogen donor. A broad range of functional groups including cyclopropane, alkene, alkyne, 4-methoxybenzyl ether, acetal, silyl ether, carbamate, cyclic ether, cyclic thioether, bromoalkane, and N-alkoxyphthalimide are well-compatible. By employing the visible light photoredox-catalyzed Reductive coupling and the subsequent optical resolution, both enantioenriched diastereomers of 2,3-dialkylated tartaric acid could be acquired conveniently