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David Crich - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of N,N,O-Trisubstituted Hydroxylamines by Stepwise Reduction and Substitution of O-Acyl N,N-Disubstituted Hydroxylamines
Organic Letters, 2016Co-Authors: Sandeep Dhanju, David CrichAbstract:Diverse N,N,O-trisubstituted Hydroxylamines, an under-represented group in compound collections, are readily prepared by partial reduction of N-acyloxy secondary amines with diisobutylaluminum hydride followed by acetylation and reduction of the so-formed O-acyl-N,N-disubstituted Hydroxylamines with triethylsilane and boron trifluoride etherate. Use of carbon nucleophiles in the last step, including allyltributylstannane, silyl enol ethers, and 2-methylfuran, gives N,N,O-trisubstituted Hydroxylamines with branching α- to the O-substituent. N,N-Disubstiuted Hydroxylamines are conveniently prepared by reaction of secondary amines with dibenzoyl peroxide followed by diisobutylaluminum hydride reduction.
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Synthesis and evaluation of di- and trimeric hydroxylamine-based β-(1→3)-glucan mimetics.
Journal of the American Chemical Society, 2014Co-Authors: Angelique Ferry, Gaelle Malik, Xavier Guinchard, Václav Vĕtvička, David CrichAbstract:Di- and trimeric hydroxylamine-based mimetics of β-(1→3)-glucans have been accessed by an asymmetric synthesis route featuring an iterative double ring-closing reductive amination reaction. These oligomeric Hydroxylamines are demonstrated to inhibit the staining of human neutrophils and of mouse macrophages by fluorescent anti-CR3 and anti-dectin-1 antibodies, respectively, and to stimulate phagocytosis, all in a linkage-dependent manner suggestive of binding to the lectin domains of complement receptor 3 (CR3) and dectin-1. The ability of these relatively short mimetics to bind to CR3 and dectin-1, as compared to the greater degree of polymerization required in β-(1→3)-glucans, is discussed in terms of the increased hydrophobicity of the α-face on replacement of the glycosidic bond by the hydroxylamine linkage.
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synthesis of β hydroxy o alkyl Hydroxylamines from epoxides using a convenient and versatile two step procedure
Synthesis, 2012Co-Authors: Gaelle Malik, Angelique Ferry, Xavier Guinchard, David CrichAbstract:A simple and convenient synthetic method was developed to prepare β-hydroxy O-alkyl Hydroxylamines in which base-mediated ring opening of epoxides with acetophenone oxime followed by cleavage of the oxime with 2,4-dinitrophenylhydrazine in acidic media furnished the hydroxylamine, which can be protected in situ with various N-protecting groups.
Jeffrey W Bode - One of the best experts on this subject based on the ideXlab platform.
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synthesis and reactivities of monofluoro acylboronates in chemoselective amide bond forming ligation with Hydroxylamines
Organic and Biomolecular Chemistry, 2016Co-Authors: Hidetoshi Noda, Jeffrey W BodeAbstract:The development of chemoselective reactions is a cornerstone of bioorganic chemistry and chemical ligation. Our contributions in this area include the development of two mechanistically distinct amide bond forming reactions, the α-ketoacid–hydroxylamine (KAHA) ligation for the chemical synthesis of proteins and the potassium acyltrifluoroborate (KAT) ligation for bioconjugation. The remarkable stability and unique reactivity of KATs with Hydroxylamines prompted us to explore other acylborons as a ligation partner, which have been unappreciated in synthetic organic chemistry. A new convenient synthetic route was devised from KATs and suitable bidentate ligands, allowing for the preparation of a wide range of new acylboronates that retain one fluoride ligand on the boron. Our results established that a ligand on the boron is responsible for their reactivity and stability and provide a firm basis for further development of the acylboron–hydroxylamine amide bond forming ligation.
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Organic Syntheses - Amide Formation by Decarboxylative Condensation of Hydroxylamines and α‐Ketoacids: N‐[(1S)‐1 Phenylethyl]‐Benzeneacetamide
Organic Syntheses, 2010Co-Authors: Lei Ju, Jeffrey W BodeAbstract:Phenylpyruvic acid Dimethylformamide (S)-(a-Methylbenzyl)hydroxylamine oxalate salt Benzeneacetamide, N-[1S)-1-phenylethyl] Keywords: Amide formation; Decarboxylative condensation; Hydroxylamines; alpha-Ketoacids; Amide bond; Activating agents; Ligation. Functionalities; Waste disposal
Andre M Beauchemin - One of the best experts on this subject based on the ideXlab platform.
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simple reaction conditions for the formation of ketonitrones from ketones and Hydroxylamines
Journal of Organic Chemistry, 2009Co-Authors: Jennifer Y Pfeiffer, Andre M BeaucheminAbstract:The condensation of ketones and Hydroxylamines to form ketonitrones was reinvestigated by using thermal conditions previously found to minimize hydroxylamine decomposition (t-BuOH, 110 °C). This simple approach allows the formation of exocyclic, acyclic, and α,β-unsaturated ketonitrones with benzylic, linear, and branched nitrogen substituents in modest to excellent isolated yields.
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intermolecular cope type hydroamination of alkenes and alkynes using Hydroxylamines
Journal of the American Chemical Society, 2008Co-Authors: Joseph Moran, Serge I Gorelsky, Elena Dimitrijevic, Marieeve Lebrun, Annecatherine Bedard, Catherine Seguin, Andre M BeaucheminAbstract:The development of the Cope-type hydroamination as a method for the metal- and acid-free intermolecular hydroamination of Hydroxylamines with alkenes and alkynes is described. Aqueous hydroxylamine reacts efficiently with alkynes in a Markovnikov fashion to give oximes and with strained alkenes to give N-alkylHydroxylamines, while unstrained alkenes are more challenging. N-AlkylHydroxylamines also display similar reactivity with strained alkenes and give modest to good yields with vinylarenes. Electron-rich vinylarenes lead to branched products while electron-deficient vinylarenes give linear products. A beneficial additive effect is observed with sodium cyanoborohydride, the extent of which is dependent on the structure of the hydroxylamine. The reaction conditions are found to be compatible with common protecting groups, free OH and NH bonds, as well as bromoarenes. Both experimental and theoretical results suggest the proton transfer step of the N-oxide intermediate is of vital importance in the interm...
Antonio Togni - One of the best experts on this subject based on the ideXlab platform.
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o trifluoromethylation of n n disubstituted Hydroxylamines with hypervalent iodine reagents
European Journal of Organic Chemistry, 2014Co-Authors: Vaclav Matousek, Ewa Pietrasiak, Lukas Sigrist, Barbara Czarniecki, Antonio TogniAbstract:A mild trifluoromethylation reaction of N,N-disubstituted Hydroxylamines that is tolerant towards a variety of functional groups, including nitriles, alcohols, ketones, esters, amides, imides, and nitrogen heterocycles, is reported. The key feature of this reaction is the activation of the CF3 reagent with either trimethylsilyl triflate or LiClO4 and partial or full deprotonation of the substrate with tetramethylguanidine or lithium diisopropylamide. Products were obtained in up to 80 % yield. Preliminary mechanistic studies suggested that the reaction follows a radical pathway in which the deprotonated hydroxylamine and a Lewis or Bronsted acid activated CF3 reagent engages in a single-electron-transfer step to generate a pair of radicals that recombine to afford the desired product. The trifluoromethylation procedure was successfully used in the modification of secondary nitrogen groups of pharmaceutically relevant targets (Fluoxetine and Mefloquine), which afforded new derivatives containing a novel N-trifluoromethoxy moiety.
Vaclav Matousek - One of the best experts on this subject based on the ideXlab platform.
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o trifluoromethylation of n n disubstituted Hydroxylamines with hypervalent iodine reagents
European Journal of Organic Chemistry, 2014Co-Authors: Vaclav Matousek, Ewa Pietrasiak, Lukas Sigrist, Barbara Czarniecki, Antonio TogniAbstract:A mild trifluoromethylation reaction of N,N-disubstituted Hydroxylamines that is tolerant towards a variety of functional groups, including nitriles, alcohols, ketones, esters, amides, imides, and nitrogen heterocycles, is reported. The key feature of this reaction is the activation of the CF3 reagent with either trimethylsilyl triflate or LiClO4 and partial or full deprotonation of the substrate with tetramethylguanidine or lithium diisopropylamide. Products were obtained in up to 80 % yield. Preliminary mechanistic studies suggested that the reaction follows a radical pathway in which the deprotonated hydroxylamine and a Lewis or Bronsted acid activated CF3 reagent engages in a single-electron-transfer step to generate a pair of radicals that recombine to afford the desired product. The trifluoromethylation procedure was successfully used in the modification of secondary nitrogen groups of pharmaceutically relevant targets (Fluoxetine and Mefloquine), which afforded new derivatives containing a novel N-trifluoromethoxy moiety.
