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Michael L. Neidig - One of the best experts on this subject based on the ideXlab platform.
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Iron(II) Active Species in Iron-Bisphosphine Catalyzed Kumada and Suzuki-Miyaura Cross-Couplings of Phenyl Nucleophiles and Secondary Alkyl Halides.
Journal of the American Chemical Society, 2015Co-Authors: Stephanie L Daifuku, Benjamin E R Snyder, Jared L Kneebone, Michael L. NeidigAbstract:While previous studies have identified FeMes2(SciOPP) as the active catalyst species in iron–SciOPP catalyzed Kumada Cross-Coupling of mesitylmagnesium bromide and primary alkyl halides, the active catalyst species in Cross-Couplings with phenyl nucleophiles, where low valent iron species might be prevalent due to accessible reductive elimination pathways, remains undefined. In the present study, in situ Mossbauer and magnetic circular dichroism spectroscopic studies combined with inorganic syntheses and reaction studies are employed to evaluate the in situ formed iron species and identify the active catalytic species in iron–SciOPP catalyzed Suzuki–Miyaura and Kumada Cross-Couplings of phenyl nucleophiles and secondary alkyl halides. While reductive elimination to form Fe(η6-biphenyl)(SciOPP) occurs upon reaction of FeCl2(SciOPP) with phenyl nucleophiles, this iron(0) species is not found to be kinetically competent for catalysis. Importantly, mono- and bis-phenylated iron(II)–SciOPP species that form pr...
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Isolation and Characterization of a Tetramethyliron(III) Ferrate: An Intermediate in the Reduction Pathway of Ferric Salts with MeMgBr
2015Co-Authors: Malik H. Al-afyouni, Kathlyn L. Fillman, William W. Brennessel, Michael L. NeidigAbstract:While iron-catalyzed Kumada Cross-Coupling reactions with simple iron salts have been known since the early 1970s, the nature of the in situ-formed iron species remains elusive. Herein, we report the synthesis of the homoleptic tetralkyliron(III) ferrate complex [MgCl(THF)5][FeMe4] from the reaction of FeCl3 with MeMgBr in THF. Upon warming, this distorted square-planar S = 3/2 species converts to the S = 1/2 species originally observed by Kochi and co-workers with concomitant formation of ethane, consistent with its intermediacy in the reduction pathway of FeCl3 to generate the reduced iron species involved in catalysis
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Isolation and characterization of a tetramethyliron(III) ferrate: an intermediate in the reduction pathway of ferric salts with MeMgBr.
Journal of the American Chemical Society, 2014Co-Authors: Malik H. Al-afyouni, Kathlyn L. Fillman, William W. Brennessel, Michael L. NeidigAbstract:While iron-catalyzed Kumada Cross-Coupling reactions with simple iron salts have been known since the early 1970s, the nature of the in situ-formed iron species remains elusive. Herein, we report the synthesis of the homoleptic tetralkyliron(III) ferrate complex [MgCl(THF)5][FeMe4] from the reaction of FeCl3 with MeMgBr in THF. Upon warming, this distorted square-planar S = 3/2 species converts to the S = 1/2 species originally observed by Kochi and co-workers with concomitant formation of ethane, consistent with its intermediacy in the reduction pathway of FeCl3 to generate the reduced iron species involved in catalysis.
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a combined mossbauer magnetic circular dichroism and density functional theory approach for iron cross coupling catalysis electronic structure in situ formation and reactivity of iron mesityl bisphosphines
Journal of the American Chemical Society, 2014Co-Authors: Stephanie L Daifuku, Malik H Alafyouni, Benjamin E R Snyder, Jared L Kneebone, Michael L. NeidigAbstract:While iron-bisphosphines have emerged as effective catalysts for C–C Cross-Coupling, the nature of the in situ formed iron species, elucidation of the active catalysts and the mechanisms of catalysis have remained elusive. A combination of 57Fe Mossbauer and magnetic circular dichroism (MCD) spectroscopies of well-defined and in situ formed mesityl-iron(II)-SciOPP species combined with density functional theory (DFT) investigations provides the first direct insight into electronic structure, bonding and in situ speciation of mesityl-iron(II)-bisphosphines in the Kumada Cross-Coupling of MesMgBr and primary alkyl halides using FeCl2(SciOPP). Combined with freeze-trapped solution Mossbauer studies of reactions with primary alkyl halides, these studies demonstrate that distorted square-planar FeMes2(SciOPP) is the active catalyst for Cross-Coupling and provide insight into the molecular-level mechanism of catalysis. These studies also define the effects of key reaction protocol details, including the role of...
Mark R. Biscoe - One of the best experts on this subject based on the ideXlab platform.
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Nickel‐Catalyzed Kumada Cross‐Coupling Reactions of Tertiary Alkylmagnesium Halides and Aryl Bromides/Triflates.
ChemInform, 2011Co-Authors: Amruta Joshi-pangu, Chao-yuan Wang, Mark R. BiscoeAbstract:Kumada Cross-Coupling of tertiary alkylmagnesium halides with aryl bromides, triflates and alkenyl halides proceeds smoothly in the presence of a Ni—NHC catalyst.
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Nickel-catalyzed Kumada Cross-Coupling reactions of tertiary alkylmagnesium halides and aryl bromides/triflates.
Journal of the American Chemical Society, 2011Co-Authors: Amruta Joshi-pangu, Chao-yuan Wang, Mark R. BiscoeAbstract:We report a Ni-catalyzed process for the Cross-Coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.
Elizabeth R. Jarvo - One of the best experts on this subject based on the ideXlab platform.
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Harnessing C–O Bonds in Stereoselective Cross-Coupling and Cross-Electrophile Coupling Reactions
Synlett, 2020Co-Authors: Amberly B. Sanford, Elizabeth R. JarvoAbstract:We discuss our laboratory’s research in the activation of alcohol derivatives in Cross-Coupling and cross-electrophile coupling reactions. Our developed methods enable the use of secondary alcohols to afford tertiary stereogenic centers, which we applied to the synthesis of pharmaceutically relevant compounds and substructures. We first discuss the synthesis of bioactive compounds through stereospecific Kumada Cross-Coupling reactions and follow this with a discussion on the development of our stereoselective cross-electrophile coupling reaction to synthesize cyclopropanes. 1 Introduction 2 Cross-Coupling Reactions 3 Cross-Electrophile Coupling Reactions 4 Conclusion
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Stereospecific Nickel-Catalyzed Cross-Coupling Reactions of Benzylic Ethers with Isotopically-Labeled Grignard Reagents
Organic process research & development, 2015Co-Authors: David D. Dawson, Elizabeth R. JarvoAbstract:In this manuscript we highlight the potential of stereospecific nickel-catalyzed Cross-Coupling reactions for applications in the pharmaceutical industry. Using an inexpensive and sustainable nickel catalyst, we report a gram-scale Kumada Cross-Coupling reaction. Reactions are highly stereospecific and proceed with inversion at the benzylic position. We also expand the scope of our reaction to incorporate isotopically labeled substituents.
Clément Mazet - One of the best experts on this subject based on the ideXlab platform.
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A General Nickel-Catalyzed Kumada Vinylation for the Preparation of 2-Substituted 1,3-Dienes
ACS Catalysis, 2018Co-Authors: Daniele Fiorito, Sarah Folliet, Yangbin Liu, Clément MazetAbstract:The identification of two nickel(II) precatalysts for the preparation of 2-substituted 1,3-dienes by a Kumada Cross-Coupling between vinyl magnesium bromide and vinyl phosphates is described. This is noteworthy as engaging only one vinyl derivative in a transition-metal-catalyzed Cross-Coupling reaction is already reputedly challenging. Salient features of this method are its operational simplicity, the mild reaction conditions, the low catalyst loadings, the short reaction times, its scalability, and the use of stoichiometric quantities of each coupling partner. The tolerance of the two nickel catalysts to an important number of reactive functional groups and their compatibility with structurally complex molecular architectures has been extensively delineated. A Negishi variant of the reaction has been developed for even more sensitive organic functions such as ester or nitrile. Several other conjugated 1,3-dienes with various substitution patterns have been prepared by combining commercial alkenyl Grign...
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A General Nickel-Catalyzed Kumada Vinylation for the Preparation of 2‑Substituted 1,3-Dienes
2018Co-Authors: Daniele Fiorito, Sarah Folliet, Yangbin Liu, Clément MazetAbstract:The identification of two nickel(II) precatalysts for the preparation of 2-substituted 1,3-dienes by a Kumada Cross-Coupling between vinyl magnesium bromide and vinyl phosphates is described. This is noteworthy as engaging only one vinyl derivative in a transition-metal-catalyzed Cross-Coupling reaction is already reputedly challenging. Salient features of this method are its operational simplicity, the mild reaction conditions, the low catalyst loadings, the short reaction times, its scalability, and the use of stoichiometric quantities of each coupling partner. The tolerance of the two nickel catalysts to an important number of reactive functional groups and their compatibility with structurally complex molecular architectures has been extensively delineated. A Negishi variant of the reaction has been developed for even more sensitive organic functions such as ester or nitrile. Several other conjugated 1,3-dienes with various substitution patterns have been prepared by combining commercial alkenyl Grignard reagents and/or readily available alkenyl enol phosphates. Proper choice of the nickel catalyst and the reaction temperature gave access to a variety of different olefin isomers with high levels of stereocontrol. Overall, this approach affords conjugated dienes that would not be accessible otherwise and therefore provides a valuable complement to existing methods
Amruta Joshi-pangu - One of the best experts on this subject based on the ideXlab platform.
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Nickel‐Catalyzed Kumada Cross‐Coupling Reactions of Tertiary Alkylmagnesium Halides and Aryl Bromides/Triflates.
ChemInform, 2011Co-Authors: Amruta Joshi-pangu, Chao-yuan Wang, Mark R. BiscoeAbstract:Kumada Cross-Coupling of tertiary alkylmagnesium halides with aryl bromides, triflates and alkenyl halides proceeds smoothly in the presence of a Ni—NHC catalyst.
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Nickel-catalyzed Kumada Cross-Coupling reactions of tertiary alkylmagnesium halides and aryl bromides/triflates.
Journal of the American Chemical Society, 2011Co-Authors: Amruta Joshi-pangu, Chao-yuan Wang, Mark R. BiscoeAbstract:We report a Ni-catalyzed process for the Cross-Coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.
