- Conformational and structural studies of N-methylacetohydroxamic acid and of its mono- and bis-chelated uranium(VI) complexes
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The thermodynamics and kinetics of the cis/trans isomerism of N-methylacetohydroxamic acid (NMAH) and its conjugated base (NMA-) have been reinvestigated in aqueous media by 1H NMR spectroscopy. Hindered rotation around the central C
- Brandès, Stéphane,Sornosa-Ten, Alejandra,Rousselin, Yoann,Lagrelette, Mickael,Stern, Christine,Moncomble, Aurélien,Cornard, Jean-Paul,Meyer, Michel
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- Acid Dissociation Constants (Ka) and Their Temperature Dependencies (ΔHa, ΔSa) for a Series of Carbon- and Nitrogen-Substituted Hydroxamic Acids in Aqueous Solution
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The acid dissociation constants (Ka) of a series of six C- and N-substituted hydroxamic acids, R1C(O)N(OH)R2 (R1 = CH3, C6H5; R2 = H, CH3, C6H5), have been determined in aqueous solution (I = 2.0) for
- Monzyk, Bruce,Crumbliss, Alvin L.
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- An unexpected new pathway for nitroxide radical production via more reactve nitrogen-centered amidyl radical intermediate during detoxification of the carcinogenic halogenated quinones by N-alkyl hydroxamic acids
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We found previously that nitroxide radical of desferrioxamine (DFO?) could be produced from the interaction between the classic iron chelating agent desferrioxamine (DFO, an N-alkyl trihydroxamic acid) and tetrachlorohydroquinone (TCHQ), one of the carconogenic quinoind metabolites of the widely used wood preservative pentachlorophenol. However, the underlying molecular mechanism remains unclear. Here N-methylacetohydroxamic acid (N-MeAHA) was synthesized and used as a simple model compound of DFO for further mechanistic study. As expected, direct ESR studies showed that nitroxide radical of N-MeAHA (Ac-(CH3)NO?) can be produced from N-MeAHA/TCHQ. Interestingly and unexpectedly, when TCHQ was substituted by its oxidation product tetrachloro-1,4-benzoquinone (TCBQ), although Ac-(CH3)NO? could also be produced, no concurrent formation of tetrachlorosemiquinone radical (TCSQ?) and TCHQ was detected, suggesting that Ac-(CH3)NO? did not result from direct oxidation of N-MeAHA by TCSQ? or TCBQ as proposed previously. To our surprise, a new nitrogen-centered amidyl radical was found to be generated from N-MeAHA/TCBQ, which was observed by ESR with the spin-trapping agents and further unequivacally identified as Ac-(CH3)N? by HPLC-MS. The final product of amidyl radical was isolated and identified as its corresponding amine. Analogous radical homolysis mechanism was observed with other halogenated quinoid compounds and N-alkyl hydroxamic acids including DFO. Interestingly, amidyl radicals were found to induce both DNA strand breaks and DNA adduct formation, suggesting that N-alkyl hydroxamic acids may exert their potential side-toxic effects via forming the reactive amidyl radical species. This study represents the first report of an unexpected new pathway for nitroxide radical production via hydrogen abstration reaction of a more reactive amidyl radical intermediate during the detoxification of the carcinogenic polyhalogenated quinones by N-alkyl hydroxamic acids, which provides more direct experimental evidence to better explain not only our previous finding that excess DFO can provide effective but only partial protection against TCHQ (or TCBQ)-induced biological damage, and also the potential side-toxic effects induced by DFO and other N-alkyl hydroxamic acid drugs.
- Zhu, Ben-Zhan,Xu, Dan,Qin, Li,Huang, Chun-Hua,Xie, Lin-Na,Mao, Li,Shao, Jie,Kalyanaraman, Balaraman
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- Conformational analysis of a secondary hydroxamic acid in aqueous solution by NOE spectroscopy
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Hydroxamic acids are metal-binding compounds used by micro-organisms and possess applications in medicine and industry. Hydroxamic acids favor two conformations, E and Z; metal binding is limited to the Z conformation. The Z conformation may be identifiab
- Sippl, Stefanie P.,Schenck, Heather L.
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- Late-Stage Photoredox C-H Amidation of N-Unprotected Indole Derivatives: Access to N-(Indol-2-yl)amides
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The late-stage functionalization of N-unprotected indoles can be useful for modifying low-molecular-weight drugs and bioactive peptides. Whereas indole carboxamides are valuable in pharmaceutical applications, the preparation N-(indol-2-yl)amides with similar structures continues to be challenging. Herein we report on visible-light-induced late-stage photoredox C-H amidation with N-unprotected indoles and tryptophan-containing peptides, leading to the formation of N-(indol-2-yl)amide derivatives. N-Unprotected indoles and aryloxyamides that contain an electron-withdrawing group could be coupled directly to eosin Y as the photocatalyst by irradiation with a green light-emitting diode at room temperature. Mechanistic studies and density functional theory calculations indicate that the transformation might proceed through the oxidative C-H functionalization of indole with a PS? to PS?- cycle. This protocol provides a new toolkit for the late-stage modification labeling and peptide-drug conjugation of N-unprotected indole derivatives.
- Weng, Yue,Ding, Bo,Liu, Yunqing,Song, Chunlan,Chan, Lo-Ying,Chiang, Chien-Wei
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supporting information
p. 2710 - 2714
(2021/05/05)
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- Regioselective Intramolecular Allene Amidation Enabled by an EDA Complex**
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The addition of radicals to unsaturated precursors is a powerful tool for the synthesis of both carbo- and heterocyclic organic building blocks. The recent advent of mild ways to generate N-centered radicals has reignited interest in exploiting highly regio-, chemo-, and stereoselective transformations that employ these reactive intermediates. While the additions of aminyl, iminyl, and amidyl radicals to alkenes and alkynes have been well-studied, analogous additions to allenes are scarce. Allenes offer several attractive features, including potential for selective amidation at three distinct sites via judicious choice of precursor or radical source, the opportunity for axial-to-point chirality transfer, and productive trapping of vinyl or allyl radical intermediates to diversify functionality in the products. In this article, we report a regioselective addition of amidyl radicals to allenes to furnish an array of valuable N-heterocycle scaffolds.
- Liu, Lu,Ward, Robert M.,Schomaker, Jennifer M.
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supporting information
p. 13783 - 13787
(2020/10/06)
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- Base-promoted aromatic [3,3] sigmatropic rearrangement of N-acyl-O-arylhydroxylamine derivatives
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The base-promoted aromatic [3,3] sigmatropic rearrangement of N-acyl-O-arylhydroxylamines giving α-(2-hydroxyphenyl)amides was successfully demonstrated. The substrates were prepared from N-substituted hydroxylamines by N-acylation followed by copper(I)-mediated O-arylation with boronic acids. Treatment of the substrates with lithium hexamethyldisilazide (LiHMDS) in THF at 0 °C to room temperature generated the corresponding amide enolates. The aromatic [3,3] rearrangement of the enolates provided the desired products in moderate to good yields. A crossover experiment produced only intramolecular products and clarified that the reaction proceeds via the aromatic [3,3] sigmatropic rearrangement, not a bond-cleavage–recombination process. Our method is a formal α-arylation of amides.
- Tayama, Eiji,Hirano, Kazuki
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p. 665 - 673
(2019/01/04)
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- PREPARATION OF SEMICONDUCTOR FILMS
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This invention relates to a precursor material, which can be decomposed to form semiconductors and metal oxides, or more generally, materials for electronic components. The precursors comprise metal complexes of hydroxamato ligands. The invention further relates to a preparation process for thin inorganic films comprising various metals (e.g. Cu/In/Zn/Ga/Sn) and oxygen, selenium and/or sulfur. The thin films can be used in photovoltaic panels (solar cells), other semiconductor or electronic devices, and other applications using such films. The process uses molecular, metal containing precursor complexes with hydroxamato ligands. These can be combined in the process with chalcogenide sources or oxygen. Exemplarily, various metal oxides and copper-based chalcopyrites of the I-III-VI2 type are prepared with high purity at low temperatures.
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Paragraph 0083
(2016/12/22)
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- Expanded substrate scope and improved reactivity of ether-forming cross-coupling reactions of organotrifluoroborates and acetals
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Mixed acetals and organotrifluoroborates undergo BF3· OEt2-promoted cross-couplings to give dialkyl ethers under simple, mild conditions. A survey of reaction partners identified a hydroxamate leaving group that improves the regioselectivity and product yield in the BF 3·OEt2-promoted coupling reaction of mixed acetals and potassium alkynyl-, alkenyl-, aryl- and heteroaryltrifluoroborates to access substituted dialkyl ethers. This leaving group enables the reaction to proceed rapidly under mild conditions (0 °C, 5-60 min) and permits reactions with electron-deficient potassium aryltrifluoroborates that are less reactive with other acetal substrates. A study of the reaction mechanism and characterization of key intermediates by NMR spectroscopy and X-ray crystallography identified a role for the hydroxamate moiety as a reversible leaving group that serves to stabilize the key oxocarbenium intermediate and the need for a slight excess of organodifluoroborane to serve as a catalyst. A secondary role for the boron nucleophile as an activating ligand was also considered. These studies provide the basis for a general class of reagents that lead to dialkyl ethers by a simple, predictable cross-coupling reaction.
- Vo, Cam-Van T.,Mitchell, T. Andrew,Bode, Jeffrey W.
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supporting information; experimental part
p. 14082 - 14089
(2011/10/12)
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- Friedel-crafts benzylation of activated and deactivated arenes
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NO going back makes possible facile Friedel-Crafts benzylations with moderate reaction temperatures, simple reaction workups, and improved substrate scope for the formation of synthetically important diarylmethanes (see scheme). Upon complexation with BF3?OEt2, hydroxamates serve as reversible leaving groups that stabilize highly reactive carbocations. Even deactivated arenes and electron-deficient benzylhydroxamates react cleanly under these conditions.
- Schaefer, Gabriel,Bode, Jeffrey W.
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supporting information; experimental part
p. 10913 - 10916
(2012/01/02)
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- Modeling the inhibition of peptide deformylase by hydroxamic acids: Influence of the sulfur donor
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The first complexes containing both a sulfur atom and a hydroxamate moiety coordinated to a biologically relevant transition metal were synthesized as models for the structure of inhibited peptide deformylases. Two of these [(N2S)Zn(hydroxamate
- Galardon, Erwan,Giorgi, Michel,Artaud, Isabelle
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p. 1047 - 1052
(2007/10/03)
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- Process for the preparation of aldehydes and ketones
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A process for the preparation of vinyl, alkynyl or aryl aldehydes or vinyl, alkynyl or aryl ketones includes reacting vinyl-, alkynyl- and aryl- and -methylene compounds with the aid of a mediator and an oxidant, wherein the mediator is selected from the group of the aliphatic, heterocyclic or aromatic NO or NOH containing compounds.
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- Hydroxamic acids for reperfusion injury
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Compounds of formula (I) STR1 in which R and R' are each separately selected from aliphatic hydrocarbon groups, aryl groups and aliphatic hydrocarbon groups substituted by an aryl group, are of value for use in medicaments for the control of free radical induced damage arising from reperfusion injury in tissue, particularly heart damage.
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- Anionic hetero[3,3] and [3,5][ rearrangements of hydroxylamine derivatives accompanied with N-O bond cleavage
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Aromatic and aliphatic N,O-divinylhydroxylamine systems generated in situ from hydroxylamine derivatives smoothly undergo [3,3] rearrangement. The base-catalyzed formation and rearrangement of enolates or dienolates of N-aryl-O-acylhydroxylamines, N,O-dia
- Endo,Uchida,Hizatate,Shudo
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p. 1096 - 1105
(2007/10/02)
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