The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Koichi Mikami - One of the best experts on this subject based on the ideXlab platform.
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Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent
Organic Letters, 2016Co-Authors: Kohsuke Aikawa, Hiroki Serizawa, Koki Ishii, Koichi MikamiAbstract:The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (Difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the Difluoromethylated aromatic compounds in good to excellent yields. The advantages of (Difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a Difluoromethyl Group from the zinc reagent to palladium catalyst efficiently proceeds without an activator.
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Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent
2016Co-Authors: Kohsuke Aikawa, Hiroki Serizawa, Koki Ishii, Koichi MikamiAbstract:The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (Difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the Difluoromethylated aromatic compounds in good to excellent yields. The advantages of (Difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a Difluoromethyl Group from the zinc reagent to palladium catalyst efficiently proceeds without an activator
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Catalytic Asymmetric Synthesis of Tertiary Alcohols and Oxetenes Bearing a Difluoromethyl Group.
Organic Letters, 2015Co-Authors: Kohsuke Aikawa, Seiya Yoshida, Daisuke Kondo, Yuya Asai, Koichi MikamiAbstract:The catalytic asymmetric ene reaction with difluoropyruvate as an electrophile in the presence of a dicationic palladium complex is shown. This is the reliable and practical catalytic asymmetric synthesis for various α-CF2H tertiary alcohols in high yields and enantioselectivities. The reaction with isobutene can be catalyzed efficiently under solvent-free conditions with low catalyst loading (up to S/C 2000). Furthermore, difluoropyruvate is applicable to the [2 + 2] cycloaddition reaction in high yields and enantioselectivities.
Xingang Zhang - One of the best experts on this subject based on the ideXlab platform.
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chlorodifluoromethane triggered formation of Difluoromethylated arenes catalysed by palladium
Nature Chemistry, 2017Co-Authors: Zhang De-feng, Xiaping Fu, Lun An, Xingang ZhangAbstract:Chlorodifluoromethane (ClCF2H), an inexpensive and abundant industrial raw material, represents an ideal and straightforward reagent for introducing the Difluoromethyl Group. However, efficient approaches for activation of the typically inert ClCF2H are limited. Now, ClCF2H is employed via a difluorocarbene pathway for palladium-catalysed Difluoromethylation of arylboronic acids with broad substrate scope.
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Chlorodifluoromethane-triggered formation of Difluoromethylated arenes catalysed by palladium
Nature Chemistry, 2017Co-Authors: Zhang De-feng, Qiao-qiao Min, Xingang ZhangAbstract:Difluoromethylated aromatic compounds are of increasing importance in pharmaceuticals, agrochemicals and materials. Chlorodifluoromethane (ClCF2H), an inexpensive, abundant and widely used industrial raw material, represents the ideal and most straightforward Difluoromethylating reagent, but introduction of the Difluoromethyl Group (CF2H) from ClCF2H into aromatics has not been reported. Here, we describe a direct palladium-catalysed Difluoromethylation method for coupling ClCF2H with arylboronic acids and esters to generate Difluoromethylated arenes with high efficiency. The reaction exhibits a remarkably broad substrate scope, including heteroarylboronic acids, and was used for Difluoromethylation of a range of pharmaceuticals and biologically active compounds. Preliminary mechanistic studies revealed that a palladium difluorocarbene intermediate is involved in the reaction. Although numerous metal-difluorocarbene complexes have been prepared, the catalytic synthesis of Difluoromethylated or Difluoromethylenated compounds involving metal-difluorocarbene complexes has not received much attention. This new reaction therefore also opens the door to understand metal-difluorocarbene complex catalysed reactions.
Amir H. Hoveyda - One of the best experts on this subject based on the ideXlab platform.
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Practical, Broadly Applicable, α-Selective, Z-Selective, Diastereoselective, and Enantioselective Addition of Allylboron Compounds to Mono-, Di-, Tri-, and Polyfluoroalkyl Ketones
Journal of the American Chemical Society, 2017Co-Authors: Farid W. Van Der Mei, Changming Qin, Ryan J. Morrison, Amir H. HoveydaAbstract:A practical method for enantioselective synthesis of fluoroalkyl-substituted Z-homoallylic tertiary alcohols has been developed. Reactions may be performed with ketones containing a polylfluoro-, trifluoro-, difluoro-, and monofluoroalkyl Group along with an aryl, a heteroaryl, an alkenyl, an alkynyl, or an alkyl substituent. Readily accessible unsaturated organoboron compounds serve as reagents. Transformations were performed with 0.5–2.5 mol % of a boron-based catalyst, generated in situ from a readily accessible valine-derived aminophenol and a Z- or an E-γ-substituted boronic acid pinacol ester. With a Z organoboron reagent, additions to trifluoromethyl and polyfluoroalkyl ketones proceeded in 80–98% yield, 97:3 to >98:2 α:γ selectivity, >95:5 Z:E selectivity, and 81:19 to >99:1 enantiomeric ratio. In notable contrast to reactions with unsubstituted allylboronic acid pinacol ester, additions to ketones with a mono- or a Difluoromethyl Group were highly enantioselective as well. Transformations were si...
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Practical, Broadly Applicable, α‑Selective, Z‑Selective, Diastereoselective, and Enantioselective Addition of Allylboron Compounds to Mono‑, Di‑, Tri‑, and Polyfluoroalkyl Ketones
2017Co-Authors: Farid W. Van Der Mei, Changming Qin, Ryan J. Morrison, Amir H. HoveydaAbstract:A practical method for enantioselective synthesis of fluoroalkyl-substituted Z-homoallylic tertiary alcohols has been developed. Reactions may be performed with ketones containing a polylfluoro-, trifluoro-, difluoro-, and monofluoroalkyl Group along with an aryl, a heteroaryl, an alkenyl, an alkynyl, or an alkyl substituent. Readily accessible unsaturated organoboron compounds serve as reagents. Transformations were performed with 0.5–2.5 mol % of a boron-based catalyst, generated in situ from a readily accessible valine-derived aminophenol and a Z- or an E-γ-substituted boronic acid pinacol ester. With a Z organoboron reagent, additions to trifluoromethyl and polyfluoroalkyl ketones proceeded in 80–98% yield, 97:3 to >98:2 α:γ selectivity, >95:5 Z:E selectivity, and 81:19 to >99:1 enantiomeric ratio. In notable contrast to reactions with unsubstituted allylboronic acid pinacol ester, additions to ketones with a mono- or a Difluoromethyl Group were highly enantioselective as well. Transformations were similarly efficient and α- and Z-selective when an E-allylboronate compound was used, but enantioselectivities were lower. In certain cases, the opposite enantiomer was favored (up to 4:96 er). With a racemic allylboronate reagent that contains an allylic stereogenic center, additions were exceptionally α-selective, affording products expected from γ-addition of a crotylboron compound, in up to 97% yield, 88:12 diastereomeric ratio, and 94:6 enantiomeric ratio. Utility is highlighted by gram-scale preparation of representative products through transformations that were performed without exclusion of air or moisture and through applications in stereoselective olefin metathesis where Z-alkene substrates are required. Mechanistic investigations aided by computational (DFT) studies and offer insight into different selectivity profiles
Song Cao - One of the best experts on this subject based on the ideXlab platform.
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Novel synthesis of pseudopeptides bearing a Difluoromethyl Group by Ugi reaction and desulfanylation
Beilstein Journal of Organic Chemistry, 2011Co-Authors: Song CaoAbstract:Thirteen Difluoromethyl-containing pseudopeptides were synthesized by Ugi reaction using the novel building block 2,2-difluoro-2-(phenylthio)acetic acid (2) as one component, followed by removal of the phenylsulfanyl protecting Group in the presence of tributyltin hydride and azobisisobutyronitrile.
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A general strategy for construction of a Difluoromethyl compound library and its application in synthesis of pseudopeptides bearing a terminal Difluoromethyl Group
Organic and Biomolecular Chemistry, 2010Co-Authors: Song Cao, Nianjin Liu, Li Shen, Jian Zhang, Xuhong QianAbstract:We describe the development of a novel synthesis strategy that uses common reaction conditions to transform a collection of simple building blocks into complex molecules bearing a terminal Difluoromethyl Group. The core of this approach is the conscious design and synthesis of new difluorinated building blocks which contain inactive and reactive Groups on each side of the CF2 Group. The strategy is illustrated by application to the synthesis of CF2H-bearing pseudopeptides via Ugi reaction.
Kohsuke Aikawa - One of the best experts on this subject based on the ideXlab platform.
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Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent
Organic Letters, 2016Co-Authors: Kohsuke Aikawa, Hiroki Serizawa, Koki Ishii, Koichi MikamiAbstract:The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (Difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the Difluoromethylated aromatic compounds in good to excellent yields. The advantages of (Difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a Difluoromethyl Group from the zinc reagent to palladium catalyst efficiently proceeds without an activator.
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Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent
2016Co-Authors: Kohsuke Aikawa, Hiroki Serizawa, Koki Ishii, Koichi MikamiAbstract:The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (Difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the Difluoromethylated aromatic compounds in good to excellent yields. The advantages of (Difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a Difluoromethyl Group from the zinc reagent to palladium catalyst efficiently proceeds without an activator
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Catalytic Asymmetric Synthesis of Tertiary Alcohols and Oxetenes Bearing a Difluoromethyl Group.
Organic Letters, 2015Co-Authors: Kohsuke Aikawa, Seiya Yoshida, Daisuke Kondo, Yuya Asai, Koichi MikamiAbstract:The catalytic asymmetric ene reaction with difluoropyruvate as an electrophile in the presence of a dicationic palladium complex is shown. This is the reliable and practical catalytic asymmetric synthesis for various α-CF2H tertiary alcohols in high yields and enantioselectivities. The reaction with isobutene can be catalyzed efficiently under solvent-free conditions with low catalyst loading (up to S/C 2000). Furthermore, difluoropyruvate is applicable to the [2 + 2] cycloaddition reaction in high yields and enantioselectivities.