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Henri Doucet - One of the best experts on this subject based on the ideXlab platform.
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reactivity of n protected 5 2 bromophenyl tetrazoles in palladium catalyzed direct arylation of heteroarenes or fluorobenzenes
Journal of Organometallic Chemistry, 2017Co-Authors: Sabah Chikhi, Jean-françois Soulé, Safia Djebbar, Henri DoucetAbstract:Abstract A new route allowing the one-step synthesis of (2-heteroarylphenyl)tetrazole and fluorinated biphenyltetrazole derivatives is disclosed. By using 2 mol% of an air-stable diphosphine-palladium catalyst [PdCl(C 3 H 5 )(dppb)], potassium Pivalate as base and dimethylacetamide as solvent, a wide range of heteroarenes ( e.g ., thiazoles, (benzo)thiophenes, furans, pyrroles, and imidazo[1,2- a ]pyridine) and polyfluorobenzenes was easily coupled with N -protected (2-bromophenyl)tetrazoles in high yields.
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Synthesis of 2-(fluorinated aryl)pyridine derivatives via palladium-catalyzed CH bond arylation of fluorobenzenes using 2-halopyridines as aryl sources
Tetrahedron Letters, 2017Co-Authors: Rabab Boyaala, Rachid Touzani, Véronique Guerchais, Jean-françois Soulé, Henri DoucetAbstract:Abstract We report herein on palladium-catalyzed direct arylation of (poly)fluorobenzene derivatives in the presence of 2-halopyridines for the one-step synthesis of 2-[(poly)fluorinated aryl]pyridine derivatives. The reactivity of 2-bromopyridines strongly dependents on its substituents at C6 position. The reaction proceeds nicely using a diphosphine palladium catalyst, and potassium Pivalate/dimethylacetamide (PivOK/DMA) as catalytic system. The reaction was regioselective and occurred at the ortho -position of fluorine atoms.
Bruce S. King - One of the best experts on this subject based on the ideXlab platform.
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direct and nitroxyl hno mediated reactions of acyloxy nitroso compounds with the thiol containing proteins glyceraldehyde 3 phosphate dehydrogenase and alkyl hydroperoxide reductase subunit c
Journal of Medicinal Chemistry, 2013Co-Authors: Susan Mitroka, Mai E. Shoman, Jenna F. Dumond, Landon Bellavia, Omar M. Aly, Mohamed Abdelaziz, Daniel B Kimshapiro, Bruce S. KingAbstract:Nitroxyl (HNO) reacts with thiols, and this reactivity requires the use of donors with 1-nitrosocyclohexyl acetate, Pivalate, and trifluoroacetate, forming a new group. These acyloxy nitroso compounds inhibit glyceraldehyde 3-phosphate dehydrogenase (GAPDH) by forming a reduction reversible active site disulfide and a reduction irreversible sulfinic acid or sulfinamide modification at Cys244. Addition of these acyloxy nitroso compounds to AhpC C165S yields a sulfinic acid and sulfinamide modification. A potential mechanism for these transformations includes nucleophilic addition of the protein thiol to a nitroso compound to yield an N-hydroxysulfenamide, which reacts with thiol to give disulfide or rearranges to sulfinamides. Known HNO donors produce the unsubstituted protein sulfinamide as the major product, while the acetate and Pivalate give substituted sulfinamides that hydrolyze to sulfinic acids. These results suggest that nitroso compounds form a general class of thiol-modifying compounds, allowing...
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Direct and Nitroxyl (HNO)-Mediated Reactions of Acyloxy Nitroso Compounds with the Thiol-Containing Proteins Glyceraldehyde 3‑Phosphate Dehydrogenase and Alkyl Hydroperoxide Reductase Subunit C
2013Co-Authors: Susan Mitroka, Mai E. Shoman, Jenna F. Dumond, Landon Bellavia, Omar M. Aly, Mohamed Abdel-aziz, Daniel B. Kim-shapiro, Bruce S. KingAbstract:Nitroxyl (HNO) reacts with thiols, and this reactivity requires the use of donors with 1-nitrosocyclohexyl acetate, Pivalate, and trifluoroacetate, forming a new group. These acyloxy nitroso compounds inhibit glyceraldehyde 3-phosphate dehydrogenase (GAPDH) by forming a reduction reversible active site disulfide and a reduction irreversible sulfinic acid or sulfinamide modification at Cys244. Addition of these acyloxy nitroso compounds to AhpC C165S yields a sulfinic acid and sulfinamide modification. A potential mechanism for these transformations includes nucleophilic addition of the protein thiol to a nitroso compound to yield an N-hydroxysulfenamide, which reacts with thiol to give disulfide or rearranges to sulfinamides. Known HNO donors produce the unsubstituted protein sulfinamide as the major product, while the acetate and Pivalate give substituted sulfinamides that hydrolyze to sulfinic acids. These results suggest that nitroso compounds form a general class of thiol-modifying compounds, allowing their further exploration
Paul Knochel - One of the best experts on this subject based on the ideXlab platform.
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practical ni catalyzed cross coupling of unsaturated zinc Pivalates with unsaturated nonaflates and triflates
Organic Letters, 2019Co-Authors: Maximilian S Hofmayer, Ferdinand H Lutter, Lucie Grokenberger, Jeffrey M Hammann, Paul KnochelAbstract:A practical nickel-catalyzed cross-coupling of (hetero)aryl or alkynylzinc Pivalates with various unsaturated nonaflates or triflates is described. Organozinc Pivalates allow these cross-couplings to take place with high yields and a low catalyst loading (0.5 mol %). Couplings with (E)- and (Z)-alkenyl triflates proceed with retention of configuration.
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Cobalt-Catalyzed Electrophilic Aminations with Anthranils: An Expedient Route to Condensed Quinolines
2018Co-Authors: Eric Tan, Niklas Keller, Yi-hung Chen, Peter M. Zehetmaier, Andreas C. Jakowetz, Thomas Bein, Paul KnochelAbstract:The reaction of various organozinc Pivalates with anthranils provides anilines derivatives, which cyclize under acidic conditions providing condensed quinolines. Using alkenylzinc Pivalates, electron-rich arylzinc Pivalates or heterocyclic zinc Pivalates produces directly the condensed quinolines of which several structures belong to new heterocyclic scaffolds. These N-heterocycles are of particular interest for organic light emitting diodes with their high photoluminescence quantum yields and long exciton lifetimes as well as for hole-transporting materials in methylammonium lead iodide perovskites solar cells due to an optimal band alignment for holes and a large bandgap
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solid organozinc Pivalates a new class of zinc organometallics with greatly enhanced air and moisture stability
Synthesis, 2017Co-Authors: Yi-hung Chen, Mario Ellwart, Vladimir Malakhov, Paul KnochelAbstract:Organozinc species are powerful reagents for performing carbon–carbon and carbon–heteroatom bond-forming reactions in the presence of a transition-metal catalyst. However, extended applications of zinc reagents have been hampered by their moderate air- and moisture-stability. This short review presents our recent developments on the preparation of solid aryl, benzyl, heteroaryl, allyl zinc Pivalates and zinc amide enolate reagents with greatly enhanced stability toward to air and moisture. 1 Introduction 2 Preparation of Organozinc Pivalates 2.1 Using Organic Halides as Substrates 2.2 Using a Directed Metalation on Functionalized Arenes and Heteroarenes 2.3 Preparation of Solid Allylic Zinc Pivalates 3 General Reactivity Patterns of Organozinc Pivalates 3.1 General Aspects 3.2 Transition-Metal-Catalyzed Cross-Couplings 3.3 Other Carbon–Carbon Bond-Forming Reactions Using Organozinc Pivalates 3.4 Preparation and Reactions of Solid, Salt-Stabilized Zinc Amide Enolates as New, Convenient Reformatsky Reagents 4 Conclusion
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organozinc Pivalate reagents segregation solubility stabilization and structural insights
ChemInform, 2014Co-Authors: Alberto Hernangomez, Paul Knochel, Emma Herd, Eva Hevia, Alan R Kennedy, Konrad Koszinowski, Sophia M Manolikakes, Robert E Mulvey, Christoph SchnegelsbergAbstract:An opening study on organozinc Pivalate complex salts is presented with a view to the promising air and moisture stability expected for these type of metalorganic reagents.
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organozinc Pivalate reagents segregation solubility stabilization and structural insights
Angewandte Chemie, 2014Co-Authors: Alberto Hernangomez, Paul Knochel, Emma Herd, Eva Hevia, Alan R Kennedy, Konrad Koszinowski, Sophia M Manolikakes, Robert E Mulvey, Christoph SchnegelsbergAbstract:The Pivalates RZnOPiv⋅Mg(OPiv)X⋅n LiCl (OPiv=Pivalate; R=aryl; X=Cl, Br, I) stand out amongst salt-supported organometallic reagents, because apart from their effectiveness in Negishi cross-coupling reactions, they show more resistance to attack by moist air than conventional organometallic compounds. Herein a combination of synthesis, coupling applications, X-ray crystallographic studies, NMR (including DOSY) studies, and ESI mass spectrometric studies provide details of these Pivalate reagents in their own right. A p-tolyl case system shows that in [D8]THF solution these reagents exist as separated Me(p-C6H4)ZnCl and Mg(OPiv)2 species. Air exposure tests and X-ray crystallographic studies indicate that Mg(OPiv)2 enhances the air stability of aryl zinc species by sequestering H2O contaminants. Coupling reactions of Me(p-C6H4)ZnX (where X=different salts) with 4-bromoanisole highlight the importance of the presence of Mg(OPiv)2. Insight into the role of LiCl in these multicomponent mixtures is provided by the molecular structure of [(THF)2Li2(Cl)2(OPiv)2Zn].
Alessia Pascale - One of the best experts on this subject based on the ideXlab platform.
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Beyond the affinity for protein kinase C: exploring 2-phenyl-3-hydroxypropyl Pivalate analogues as C1 domain-targeting ligands
MedChemComm, 2015Co-Authors: Daniela Rossi, Gustav Boije Af Gennäs, Virpi Talman, Annamaria Marra, Pietro Picconi, Rita Nasti, Massimo Serra, Jihyae Ann, Marialaura Amadio, Alessia PascaleAbstract:Over the past fifteen years, we reported the design and synthesis of different series of compounds targeting the C1 domain of protein kinase C (PKC) that were based on various templates. Out of the Pivalate templates, 2-[4-(benzyloxy)phenyl]-3-hydroxypropyl Pivalate (compound 1) emerged as the most potent and promising PKCα ligand, showing a Ki value of 0.7 μM. In the present contribution our efforts are aimed at better understanding which structural modifications of the Pivalate template are allowed for its affinity to the C1 domain of PKC to be preserved or increased. To this aim, thirteen novel analogues of 1 were designed and their interaction with the target was evaluated in silico. Designed compounds were then prepared and fully characterized as well as their affinity for the α and δ isoforms of PKC evaluated. Additionally, in order to investigate the role of chirality in the ligand–target interaction, the pure enantiomers of the most interesting PKC ligands were prepared and their affinity for PKC isoforms was determined. Results from our study revealed that: i) the presence of the ester function seems to be essential for the ligand–target interaction; ii) only a few structural modifications at the ester group are allowed for the C1 domain affinity to be preserved; and iii) the [3H]PDBu replacement experiments showed that the C1 domain of PKC does not exhibit enantiopreference for the pure stereoisomers of tested compounds. Altogether our observations provide further insights into the ligand–target interactions of the PKC C1 domain and represent a step-forward in future development of more specific and effective PKC ligands.
Kiyoshi Tomioka - One of the best experts on this subject based on the ideXlab platform.
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contiguous radical pivaloyloxymethylation directed c sp3 h iodination of n tosyl cycloalkanecarbaldimine
Tetrahedron Letters, 2015Co-Authors: Shintaro Fujii, Mayu Nakano, Yousuke Yamaoka, Kiyosei Takasu, Kenichi Yamada, Kiyoshi TomiokaAbstract:Abstract A reaction of N-tosyl cycloalkanecarbaldimines with iodomethyl Pivalate was initiated by triethylborane to give pivaloyloxymethylated products bearing 3-iodocycloalkyl groups. Radical addition of pivaloyloxymethyl to imines generates aminyl radicals, which then regioselectively cleave C H bonds at the 3-position of the cycloalkane moieties. The resulting carbon-centered radicals are trapped with iodine. DFT calculations rationalized stereo- and regioselectivity.