- Photoorganocatalytic One-Pot Synthesis of Hydroxamic Acids from Aldehydes
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An efficient one-pot synthesis of hydroxamic acids from aldehydes and hydroxylamine is described. A fast, visible-light-mediated metal-free hydroacylation of dialkyl azodicarboxylates was used to develop the subsequent addition of hydroxylamine hydrochloride. A range of aliphatic and aromatic aldehydes were employed in this reaction to give hydroxamic acids in high to excellent yields. Application of the current methodology was demonstrated in the synthesis of the anticancer medicine vorinostat.
- Papadopoulos, Giorgos N.,Kokotos, Christoforos G.
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- A new method for the preparation of para-substituted benzohydroxamic acids
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A new method for the preparation of para-substituted benzohydroxamic acids from para-substituted benzoic acids by using hydroxylamine hydrochloride in the presence of triphenyl phosphine and N-bromosuccinimide under mild basic conditions is described.
- Dhuru, Sameer P.,Salunkhe, Manikrao M.
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- Alternating Current Electrolysis as Efficient Tool for the Direct Electrochemical Oxidation of Hydroxamic Acids for Acyl Nitroso Diels–Alder Reactions
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The acyl nitroso Diels–Alder reaction of 1,3-dienes with electrochemically oxidised hydroxamic acids is described. By using alternating current electrolysis, their typical electro-induced decomposition could be suppressed in favour of the 1,2-oxazine cycloaddition products. The reaction was optimised using Design of Experiments (DoE) and a sensitivity test was conducted. A mixture of triethylamine/hexafluoroisopropanol served as supporting electrolyte in dichloromethane, thus giving products of high purity after evaporation of the volatiles without further purification. The optimised reaction conditions were applied to various 1,3-dienes and hydroxamic acids, giving up to 96 % isolated yield.
- F?hrmann, Jan,Hilt, Gerhard
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- Angeli-Rimini's reaction on solid support: A new approach to hydroxamic acids
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Angeli-Rimini's reaction has been performed for the first time on solid phase. A convenient one-step procedure for the synthesis of hydroxamic acids starting from aldehydes and solid-supported N-hydroxybenzenesulfonamide is reported. The hydroxamates are isolated in good to high yields and purities by simple evaporation of the volatile solvents, after treatment of the crude reaction mixture with sequestering agents.
- Porcheddu, Andrea,Giacomelli, Giampaolo
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- Straightforward synthesis of 4,5-bifunctionalized 1,2-oxazinanes via Lewis acid promoted regio- and stereo-selective nucleophilic ring-opening of 3,6-dihydro-1,2-oxazine oxides
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Functionalized 1,2-oxazinanes are interesting and valuable heterocycles with potential applications in synthetic and medicinal chemistry. A straightforward strategy for quick access to unprecedented trans-4-hydroxyl-5-azido/cyano/amino 1,2-oxazinanes are developed: N-COR 3,6-dihydro- 1,2-oxazine oxides are prepared with ease from related dihydro- 1,2-oxazines and opened by nucleophiles TMSN3, TMSCN and aryl/alkyl amines. Appropriate Lewis acid catalysts are found playing a vital role for both reaction rate and regioselectivity. The N-COR group can be removed under mild conditions to provide highly desirable NH 1,2-oxazinanes inaccessible via previous methods.
- Huang, Xiu-Rong,Zhang, Yu-Mei,Wan, Ting-Biao,Zhang, Piao,Zhang, Xiu-Xiu,Wang, Fang-Ming,Xu, Defeng,Shen, Mei-Hua,Xu, Hua-Dong
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- Cytotoxicity, alpha-glucosidase inhibition and molecular docking studies of hydroxamic acid chromium(III) complexes
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Hydroxamic acids [R(CO)N(OH)R’] are flexible compounds for organic and inorganic analyses due to their frailer structures compared to the carboxylic acid. The syntheses and characterization of benzohydroxamic acid (BHA), its CH3–, OCH3/su
- Abdullah, Faiezah,Anouar, El Hassane,Bahron, Hadariah,Hassan, Latifah Robbaniyyah,Mohd Tajuddin, Amalina
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- Carbonic anhydrase inhibitors. Inhibition of the β-class enzymes from the fungal pathogens Candida albicans and Cryptococcus neoformans with branched aliphatic/aromatic carboxylates and their derivatives
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The inhibition of the β-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic fungi Cryptococcus neoformans (Can2) and Candida albicans (Nce103) with a series of 25 branched aliphatic and aromatic carboxylates has been investigated. Human isoforms hCA I and II were also included in the study for comparison. Aliphatic carboxylates were generally millimolar hCA I and II inhibitors and low micromolar/submicromolar β-CA inhibitors. Aromatic carboxylates were micromolar inhibitors of the four enzymes but some of them showed low nanomolar activity against the fungal pathogenic enzymes. 4-Hydroxy- and 4-methoxy-benzoate inhibited Can2 with KIs of 9.5-9.9 nM. The methyl esters, hydroxamates, hydrazides and carboxamides of some of these derivatives were also effective inhibitors of the α- and β-CAs investigated here.
- Carta, Fabrizio,Innocenti, Alessio,Hall, Rebecca A.,Mühlschlegel, Fritz A.,Scozzafava, Andrea,Supuran, Claudiu T.
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- Cu(II)-Catalyzed C-H Amidation/Cyclization of Azomethine Imines with Dioxazolones via Acyl Nitrenes: A Direct Access to Diverse 1,2,4-Triazole Derivatives
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We report a Cu(II)-catalyzed C-H amidation/cyclization of azomethine imines with dioxazolones as acyl nitrene transfer reagents under additive-and ligand-free conditions. An array of 1,2,4-triazolo[1,5-a]pyridine derivatives were afforded in moderate to good yields with excellent functional group tolerance. In addition, scale-up reaction and photoluminescence properties were discussed.
- Liu, Xiang,Li, Wen,Jiang, Wenxuan,Lu, Hao,Liu, Jiali,Lin, Yijun,Cao, Hua
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supporting information
p. 613 - 618
(2022/01/20)
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- Silver-Catalyzed Acyl Nitrene Transfer Reactions Involving Dioxazolones: Direct Assembly of N-Acylureas
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Dioxazolones and isocyanides are useful synthetic building blocks, and have attracted significant attention from researchers. However, the silver-catalyzed nitrene transfer reaction of dioxazolones has not been investigated to date. Herein, a silver-catalyzed acyl nitrene transfer reaction involving dioxazolones, isocyanides, and water was realized in the presence of Ag2O to afford a series of N-acylureas in moderate to good yields.
- Yang, Zheng-Lin,Xu, Xin-Liang,Chen, Xue-Rong,Mao, Zhi-Feng,Zhou, Yi-Feng
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supporting information
p. 648 - 652
(2020/12/21)
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- Photochemical Activation of Aromatic Aldehydes: Synthesis of Amides, Hydroxamic Acids and Esters
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A cheap, facile and metal-free photochemical protocol for the activation of aromatic aldehydes has been developed. Utilizing thioxanthen-9-one as the photocatalyst and cheap household lamps as the light source, a variety of aromatic aldehydes have been activated and subsequently converted in a one-pot reaction into amides, hydroxamic acids and esters in good to high yields. The applicability of this method was highlighted in the synthesis of Moclobemide, a drug against depression and social anxiety. Extended and detailed mechanistic studies have been conducted, in order to determine a plausible mechanism for the reaction.
- Nikitas, Nikolaos F.,Apostolopoulou, Mary K.,Skolia, Elpida,Tsoukaki, Anna,Kokotos, Christoforos G.
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p. 7915 - 7922
(2021/05/03)
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- P(III)-Assisted Electrochemical Access to Ureas via in situ Generation of Isocyanates from Hydroxamic Acids
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An external oxidant-free protocol for the generation of isocyanates from hydroxamic acids assisted by trivalent phosphine under mild electrochemical conditions was reported. The process started with the anodic oxidation of hydroxamic acids, followed by reacting with phosphine to form corresponding alkoxyphosphoniums and subsequent rearrangement with the release of tri-substituted phosphine oxide as the driving force to give isocyanates, which were trapped by N-based nucleophiles to produce various ureas. This method provides a broadly applicable procedure to access isocyanate intermediates under mild electrochemical conditions.
- Meng, Haiwen,Sun, Kunhui,Xu, Zhimin,Tian, Lifang,Wang, Yahui
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supporting information
p. 1768 - 1772
(2021/03/26)
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- Palladium-Catalyzed 5-exo-dig Cyclization Cascade, Sequential Amination/Etherification for Stereoselective Construction of 3-Methyleneindolinones
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An cascade intramolecular 5-exo-dig cyclization of N-(2-iodophenyl)propiolamides and sequential amination/etherification (with N-hydroxybenzamides, phenyl hydroxycarbamate) protocol for the synthesis of amino- and phenoxy-substituted 3-methyleneindolinones using unexpensive Pd(PPh3)4 as catalyst has been developed. The protocol enables the assembly of structurally important oxindole cores featuring moderate functional group tolerance (particularly the halo group), affording a broad spectrum of products with diverse substituents in good to excellent yields. (Figure presented.).
- Zuo, Youpeng,He, Xinwei,Tang, Qiang,Hu, Wangcheng,Zhou, Tongtong,Hu, Wenbo,Shang, Yongjia
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p. 2117 - 2123
(2020/12/22)
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- Thioether-Directed NiH-Catalyzed Remote γ-C(sp3)-H Hydroamidation of Alkenes by 1,4,2-Dioxazol-5-ones
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A NiH-catalyzed thioether-directed cyclometalation strategy is developed to enable remote methylene C-H bond amidation of unactivated alkenes. Due to the preference for five-membered nickelacycle formation, the chain-walking isomerization initiated by the NiH insertion to an alkene can be terminated at the γ-methylene site remote from the alkene moiety. By employing 2,9-dibutyl-1,10-phenanthroline as the ligand and dioxazolones as the reagent, the amidation occurs at the γ-C(sp3)-H bonds to afford the amide products in up to 90% yield (>40 examples) with remarkable regioselectivity (up to 24:1 rr).
- Chen, Qishu,Du, Bingnan,Ouyang, Yuxin,Yu, Wing-Yiu
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supporting information
p. 14962 - 14968
(2021/09/29)
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- Direct synthesis of benzoxazinones via Cp*Co(III)-catalyzed C–H activation and annulation of sulfoxonium ylides with dioxazolones
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A highly novel and direct synthesis of benzoxazinones was developed via Cp*Co(III)-catalyzed C–H activation and [3 + 3] annulation between sulfoxonium ylides and dioxazolones. The reaction is conducted under base-free conditions and tolerates various functional groups. Starting from diverse readily available sulfoxonium ylides and dioxazolones, a variety of benzoxazinones could be synthesized in one step in 32%-75% yields.
- Yu, Yongqi,Xia, Zhen,Wu, Qianlong,Liu, Da,Yu, Lin,Xiao, Yuanjiu,Tan, Ze,Deng, Wei,Zhu, Gangguo
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supporting information
p. 1263 - 1266
(2020/10/08)
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- Synthesis of sulfimides and N-Allyl-N-(thio)amides by Ru(II)catalyzed nitrene transfer reactions of N-acyloxyamides
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The N-acyloxyamides were employed as effective N-acyl nitrene precursors in reactions with thioethers under the catalysis of a commercially available Ru(II) complex, from which a variety of sulfimides were synthesized efficiently and mildly. If an allyl group is contained in the thioether precursor, the [2,3]-sigmatropic rearrangement of the sulfimide occurs simultaneously and the N-allyl-N-(thio)amides were obtained as the final products. Preliminary mechanistic studies indicated that the Ru-nitrenoid species should be a key intermediate in the transformation.
- Zhang, Xinyu,Lin, Bo,Chen, Jianhui,Chen, Jiajia,Luo, Yanshu,Xia, Yuanzhi
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supporting information
p. 819 - 825
(2021/02/01)
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- Palladium-catalyzed cascade decarboxylative amination/6- endo-dig benzannulation of o-alkynylarylketones with n-hydroxyamides to access diverse 1-naphthylamine derivatives
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An efficient and practical one-pot strategy to produce highly substituted 1-naphthylamines via sequential palladium-catalyzed decarboxylative amination/intramolecular 6-endo-dig benzannulation reactions has been described. In this reaction, a broad range of electron-rich, electron-neutral, and electron-deficient o-alkynylarylketones react well with N-hydroxyl aryl/alkylamides to give a diversity of 1-naphthylamines in good to excellent yields under mild reaction conditions. The gram-scale synthesis, with benefits such as undiminished product yield and easy transformation, illustrated the practicality of this method.
- Zuo, Youpeng,He, Xinwei,Tang, Qiang,Hu, Wangcheng,Zhou, Tongtong,Shang, Yongjia
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p. 3890 - 3894
(2020/05/18)
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- Divergent Synthesis of Tunable Cyclopentadienyl Ligands and Their Application in Rh-Catalyzed Enantioselective Synthesis of Isoindolinone
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A series of rhodium complexes bearing sterically and electronically tunable cyclopentadienyl ligands, prepared by utilizing Co2(CO)8-mediated [2+2+1] cyclization as a key step, were synthesized. In the presence of 2.5 mol% of CpmRh4, unprecedented enantioselective [4+1] annulation reaction of benzamides and alkenes was achieved with a broad substrate scope under mild reaction conditions, providing a variety of isoindolinones with excellent regio-and enantioselectivity (up to 94% yield, 97:3 er). Preliminary mechanistic studies suggest that the reaction involves an oxidative Heck reaction and an intramolecular enantioselective alkene hydroamination reaction.
- Cui, Wen-Jun,Wu, Zhi-Jie,Gu, Qing,You, Shu-Li
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p. 7379 - 7385
(2020/08/19)
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- RhIII-Catalyzed C?H Activation of Aryl Hydroxamates for the Synthesis of Isoindolinones
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RhIII-catalyzed C?H functionalization reaction yielding isoindolinones from aryl hydroxamates and ortho-substituted styrenes is reported. The reaction proceeds smoothly under mild conditions at room temperature, and tolerates a range of functional groups. Experimental and computational investigations support that the high regioselectivity observed for these substrates results from the presence of an ortho-substituent embedded in the styrene. The resulting isoindolinones are valuable building blocks for the synthesis of bioactive compounds. They provide easy access to the natural-product-like compounds, isoindolobenzazepines, in a one-pot two-step reaction. Selected isoindolinones inhibited Hedgehog (Hh)-dependent differentiation of multipotent murine mesenchymal progenitor stem cells into osteoblasts.
- Shaaban, Saad,Davies, Caitlin,Merten, Christian,Flegel, Jana,Otte, Felix,Strohmann, Carsten,Waldmann, Herbert
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supporting information
p. 10729 - 10734
(2020/07/25)
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- Co(III)-Catalyzed C-H Amidation of Nitrogen-Containing Heterocycles with Dioxazolones under Mild Conditions
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A cobalt(III)-catalyzed C-8 selective C-H amidation of quinoline N-oxide using dioxazolone as an amidating reagent under mild conditions is disclosed. The reaction proceeds efficiently with excellent functional group compatibility. The utility of the current method is demonstrated by gram scale synthesis of C-8 amide quinoline N-oxide and by converting this amidated product into functionalized quinolines. Furthermore, the developed catalytic method is also applicable for C-7 amidation of N-pyrimidylindolines and ortho-amidation of benzamides.
- Dhiman, Ankit Kumar,Thakur, Ankita,Kumar, Inder,Kumar, Rakesh,Sharma, Upendra
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p. 9244 - 9254
(2020/08/14)
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- Chiral amination sulfoxide and preparation method thereof (by machine translation)
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The invention belongs to the field of organic synthesis, and discloses chiral amination sulfoxide which has the structure of a general formula I. Wherein R is hydrogen or R1 And R2 Each independently selected from one of the following structures: hydrogen, alkyl, alkoxy, ester, trifluoromethyl, trifluoromethoxy, trifluoromethylthio. Halogens, alkynyl groups, alkenyl groups, amino groups, cyano groups, hydroxyl groups, aldehyde groups, carboxyl groups, nitro groups, amide groups, benzene rings, and bonded benzene ring fused rings to naphthalene; R3 Selected from the group consisting of phenyl, optionally substituted phenyl, aryl, heteroaryl, styryl, alkyl, haloalkyl and the like. The method comprises the following steps: forming a complex with a tert-butyl cyclopentadienyl metal iridium complex, forming a complex with the modified chiral proline, and activating C-H bond of enantioselective induced sulfoxide to obtain chiral sulphoxide. The synthetic method disclosed by the invention is high in yield and good in enantioselectivity, and the obtained amidated sulfoxide can be derivatized to obtain a chiral ligand. (by machine translation)
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Paragraph 0245-0247; 0251-0253
(2020/11/12)
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- Synthesis, characterization and assessment of local anesthetic activity of some benzohydroxamic acids
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In the present investigation, 6 compounds (E1-E6) were synthesized by reaction of ethyl esters of p-substituted benzoic acid with hydroxylamine. The chemical structures of the synthesized hydroxamic acids were verified on the basis of spectral analysis (IR, 1H NMR, 13C NMR and mass spectra). The benzohydroxamic acids were examined for potential local anesthetic activity using foot withdrawal reflex of the frog and benzocaine was used as standard drug. Compounds were tested at two different solvents; 5 % DMSO and 0.65 % NaOH, each solution was tested at three different concentration levels (40, 100 and 200 μg/mL). Local anesthetic activity of the compounds differed according to the concentration level and selected solvent. Compounds E4 and E5 were found to be the most active and were comparable to the standard drug in tested solvents at all investigated concentrations. All compounds displayed an enhanced activity in the the aqueous basic solutions.
- Aldeen, Ekhlas Sheakh,Elsaman, Tilal,Mohamed, Malik Suliman,Adam, Mohamed E.,Mohamed, Magdi Awadalla
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p. 181 - 185
(2018/12/11)
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- Dioxazolones as masked ester surrogates in the Pd(ii)-catalyzed direct C-H arylation of 6,5-fused heterocycles
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A simple and effective Pd(ii)-catalyzed regioselective C(2)-H arylation of 6,5-fused heterocycles with dioxazolones as a masked ester surrogate under mild conditions is reported. The significance of the arylation is highlighted by the new reactivity demonstrated in dioxazolones via proximal C-H activation of the cyclic carbonate of the hydroxamic acid functionality under protic conditions.
- Saxena, Paridhi,Maida, Neha,Kapur, Manmohan
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supporting information
p. 11187 - 11190
(2019/09/30)
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- Rhodium(iii)-catalyzed cascade reactions of benzoic acids with dioxazolones: Discovery of 2,5-substituted benzoxazinones as AIE molecules
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A rhodium-catalyzed cascade reaction of benzoic acids with 1,4,2-dioxazol-5-ones was studied. The carboxyl group enabled a double C-H amidation followed by further intramolecular cyclization to afford 2,5-substituted benzoxazinones, which exhibited aggregation-induced emission (AIE) properties with a promising excited-state intramolecular proton-transfer (ESIPT) phenomenon.
- Li, Jinbiao,Zhang, Shuaizhong,Lonka, Madhava Reddy,Zhang, Jinquan,Zou, Hongbin
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supporting information
p. 11203 - 11206
(2019/09/30)
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- Cobalt-Catalyzed Ortho-C(sp2)-H Amidation of Benzaldehydes with Dioxazolones Using Transient Directing Groups
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An efficient and convenient cobalt-catalyzed ortho-C(sp2)-H amidation of benzaldehydes employing dioxazolones as the aminating reagent has been developed. The key feature of this protocol is the use of green and economic earth-abundant metals c
- Huang, Jie,Ding, Jun,Ding, Tong-Mei,Zhang, Shuiyi,Wang, Yaqiu,Sha, Feng,Zhang, Shu-Yu,Wu, Xin-Yan,Li, Qiong
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supporting information
p. 7342 - 7345
(2019/10/02)
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- Efficient Copper-Catalyzed Multicomponent Synthesis of N-Acyl Amidines via Acyl Nitrenes
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Direct synthetic routes to amidines are desired, as they are widely present in many biologically active compounds and organometallic complexes. N-Acyl amidines in particular can be used as a starting material for the synthesis of heterocycles and have several other applications. Here, we describe a fast and practical copper-catalyzed three-component reaction of aryl acetylenes, amines, and easily accessible 1,4,2-dioxazol-5-ones to N-acyl amidines, generating CO2 as the only byproduct. Transformation of the dioxazolones on the Cu catalyst generates acyl nitrenes that rapidly insert into the copper acetylide Cu-C bond rather than undergoing an undesired Curtius rearrangement. For nonaromatic dioxazolones, [Cu(OAc)(Xantphos)] is a superior catalyst for this transformation, leading to full substrate conversion within 10 min. For the direct synthesis of N-benzoyl amidine derivatives from aromatic dioxazolones, [Cu(OAc)(Xantphos)] proved to be inactive, but moderate to good yields were obtained when using simple copper(I) iodide (CuI) as the catalyst. Mechanistic studies revealed the aerobic instability of one of the intermediates at low catalyst loadings, but the reaction could still be performed in air for most substrates when using catalyst loadings of 5 mol %. The herein reported procedure not only provides a new, practical, and direct route to N-acyl amidines but also represents a new type of C-N bond formation.
- Van Vliet, Kaj M.,Polak, Lara H.,Siegler, Maxime A.,Van Der Vlugt, Jarl Ivar,Guerra, Célia Fonseca,De Bruin, Bas
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supporting information
p. 15240 - 15249
(2019/10/19)
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- A new synthetic route to acylnitroso intermediates and their applications in HDA and ene reactions
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Background: Acylnitroso intermediates are considered as highly reactive and useful transient that have been used to synthesize a broad class of biological active compounds and synthetic drugs. Although there are some reported methods for the generation of these intermediates, but still challenge for mild and environmental benign protocol. Herein, we report the facile in situ synthesis of acylnitroso intermediates and their efficient hetero Diels-Alder (HDA) and ene reactions. Methods: Acylnitroso intermediates were readily obtained by hydrogen peroxide oxidation of hydroxamic acids catalyzed by Cu(I)-, Ir(I)- or Ru(II)-complexes and easily reacted with symmetric and asymmetric conjugated dienes beside their reaction with different alkenes which converted to biological active products. Results: The resulted acylnitroso intermediates were efficiently afforded the hetero Diels-Alder cycloadducts in the presence of cyclopentadiene, cyclohexadiene or α-terpinene in high yields along with good regioselectivity for the later. In case of N-dienyl lactams, the cycloadducts were formed in the yield up to 89% with complete regioselectivity. In the presence of optically active N-dienyl pyroglutamates, diastereoisomers were formed in high yields with up to 72 de. In addition, the transient acylnitroso species were trapped with alkene to form the ene product in yield up to 95 %. As an interesting transformation, the halocyclization of the ene products gave substituted oxazolidone in 77% yield which considered as one of the effective antimicrobial and antibiotic compounds. Conclusion: In a brief, we introduce a mild and effective route to deliver acylnitroso intermediates in situ by using environmentally benign, cost effective, and non-toxic hydrogen peroxide oxidant catalyzed by Cu(I)-, Ir(I)- or Ru(II)-complexes. Good to excellent yields, regio- and diastereoselectivity were obtained by trapping these intermediates in symmetric and asymmetric HDA and ene reactions. Interestingly, the ene products easily transformed to potent drugs.
- Fakhruddin, Ahmad,Abu-Elfotoh, Abdel-Moneim,Shibatomi, Kazutaka,Iwasa, Seiji
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supporting information
p. 196 - 205
(2018/03/09)
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- Consecutive Lossen rearrangement/transamidation reaction of hydroxamic acids under catalyst- and additive-free conditions
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The Lossen rearrangement is a classic process for transforming activated hydroxamic acids into isocyanate under basic or thermal conditions. In the current report we disclosed a consecutive Lossen rearrangement/transamidation reaction in which unactivated hydroxamic acids were converted into N-substituted formamides in a one-pot manner under catalyst- and additive-free conditions. One feature of this novel transformation is that the formamide plays triple roles in the reaction by acting as a readily available solvent, a promoter for additive-free Lossen rearrangement, and a source of the formyl group in the final products. Acyl groups other than formyl could also be introduced into the product when changing the solvent to other low molecular weight aliphatic amide derivatives. The solvent-promoted Lossen rearrangement was better understood by DFT calculations, and the intermediacy of isocyanate and amine was supported well by experiments, in which the desired products were obtained in excellent yields under similar conditions. Not only monosubstituted formamides were synthesized from hydroxamic acids, but also N,N-disubstituted formamides were obtained when secondary amines were used as precursors.
- Jia, Mengmeng,Zhang, Heng,Lin, Yongjia,Chen, Dimei,Chen, Yanmei,Xia, Yuanzhi
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p. 3615 - 3624
(2018/05/26)
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- Experimental and computational studies on H2O-promoted, Rh-catalyzed transient-ligand-free ortho-C(sp2)-H amidation of benzaldehydes with dioxazolones
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An efficient and convenient ligand-free, rhodium-catalyzed ortho-C(sp2)-H amidation of benzaldehydes with dioxazolones using H2O as the key promoter is described. Using this protocol, a wide range of benzaldehyde substrates were selectively amidated in good to excellent yields with broad functional group compatibility. KIE experiments revealed that the C-H bond activation was likely the rate-limiting step. In addition, computational studies indicated that the catalyst precursor interacted with water and dioxazolones to generate the active catalytic species. Notably, the practicality and efficacy of this method were illustrated by a late-stage amidation of an estrone-derived molecule and further transformations of the amidated product.
- Ding, Jun,Jiang, Wei,Bai, He-Yuan,Ding, Tong-Mei,Gao, Dafang,Bao, Xiaoguang,Zhang, Shu-Yu
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supporting information
p. 8889 - 8892
(2018/08/17)
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- Tf2NH-Catalyzed Formal [3 + 2] Cycloaddition of Ynamides with Dioxazoles: A Metal-Free Approach to Polysubstituted 4-Aminooxazoles
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An unprecedented Tf2NH-catalyzed formal [3 + 2] cycloaddition of ynamides with dioxazoles was developed to construct various polysubstituted 4-aminooxazoles. This approach features a metal-free catalytic bimolecular assembly of oxazole motifs, a low-cost catalyst, exceptionally mild reaction conditions, a very short reaction time, a broad substrate scope, and high efficiency. This metal-free protocol may find applications in pharmaceutical-oriented synthesis.
- Zhao, Yingying,Hu, Yancheng,Wang, Chunxiang,Li, Xincheng,Wan, Boshun
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p. 3935 - 3942
(2017/04/11)
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- Dioxazoles, a new mild nitrene transfer reagent in gold catalysis: Highly efficient synthesis of functionalized oxazoles
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A gold-catalyzed regioselective [3+2] cycloaddition of ynamides with 1,4,2-dioxazoles was developed and offers a novel approach to obtain highly functionalized oxazoles under mild reaction conditions. 1,4,2-Dioxazole was found to act as an efficient N-acyl nitrene equivalent to trigger a facile generation of α-imino gold-carbene intermediate through the elimination of a ketone.
- Chen, Ming,Sun, Ning,Chen, Haoyi,Liu, Yuanhong
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supporting information
p. 6324 - 6327
(2016/05/19)
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- A base-mediated self-propagative Lossen rearrangement of hydroxamic acids for the efficient and facile synthesis of aromatic and aliphatic primary amines
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A variety of aromatic and aliphatic hydroxamic acids were converted to the corresponding primary amines via base-mediated rearrangement. This rearrangement could proceed with less than 1 equiv. of K2CO3 in polar solvents under thermal conditions with no external reagents. This rearrangement has several features including no external activating agents needed for promoting the rearrangement, less than one equivalent of a base is sufficient for the reaction, and a clean reaction in which only carbon dioxide is produced as a by-product. A self-propagating mechanism via an isocyanate intermediate is proposed and elementary reaction steps, namely, chain propagation reactions are supported by experiments.
- Ohtsuka, Naoya,Okuno, Moriaki,Hoshino, Yujiro,Honda, Kiyoshi
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supporting information
p. 9046 - 9054
(2016/10/05)
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- One-pot synthesis of hydroxamic acids from aldehydes and hydroxylamine
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A one-pot oxidative transformation of aldehydes into hydroxamic acids by the use of an aqueous solution of hydroxylamine is reported. The methodology gives high yields and makes use of cheap, abundant and easily available reagents.
- Dettori, Giovanna,Gaspa, Silvia,Porcheddu, Andrea,De Luca, Lidia
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supporting information
p. 2709 - 2713
(2014/09/17)
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- Rhodium-catalyzed C-H alkynylation of arenes at room temperature
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The rhodium(III)-catalyzed ortho C-H alkynylation of non-electronically activated arenes is disclosed. This process features a straightforward and highly effective protocol for the synthesis of functionalized alkynes and represents the first example of merging a hypervalent iodine reagent with rhodium(III) catalysis. Notably, this reaction proceeds at room temperature, tolerates a variety of functional groups, and more importantly, exhibits high selectivity for monoalkynylation. Hot rhod: A rhodium-catalyzed, electronically reversed Sonogashira reaction between unbiased arenes and the hypervalent iodine reagent 1 proceeds through C-H activation. This reaction displays excellent functional-group tolerance and high efficiency, and thus opens a new synthetic pathway to access functionalized alkynes. Cp=C5Me5, DCE=1,2-dichloroethane, Piv=pivaloyl, TIPS=triisopropylsilyl.
- Feng, Chao,Loh, Teck-Peng
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p. 2722 - 2726
(2014/03/21)
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- Rhodium(iii)-catalyzed formal oxidative [4 + 1] cycloaddition of benzohydroxamic acids and α-diazoesters. A facile synthesis of functionalized benzolactams
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A Rh(iii)-catalyzed oxidative [4 + 1] cycloaddition of benzohydroxamic acids and α-diazoesters is achieved to afford benzolactams in up to 93% yields. With the N-OAc amido moiety as a directing group, the ortho-C-H is selectively functionalized and the catalytic reaction exhibits excellent tolerance to different functional substituents. A notable rhodacyclic complex is isolated and structurally characterized, suggesting that C-H/N-H cyclometallation is a key step in the catalytic cycle. This journal is the Partner Organisations 2014.
- Lam, Hon-Wah,Man, Ka-Yi,Chan, Wai-Wing,Zhou, Zhongyuan,Yu, Wing-Yiu
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supporting information
p. 4112 - 4116
(2014/06/10)
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- N-methylimidazole-catalyzed synthesis of carbamates from hydroxamic acids via the lossen rearrangement
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An efficient, one-pot, N-methylimidazole (NMI) accelerated synthesis of aromatic and aliphatic carbamates via the Lossen rearrangement is reported. NMI is a catalyst for the conversion of isocyanate intermediates to the carbamates. Moreover, the utility of arylsulfonyl chloride in combination with NMI minimizes the formation of often-observed hydroxamate-isocyanate dimers during the sequence. Under the present conditions, lowering of temperatures is also possible, enabling a mild protocol.
- Yoganathan, Sabesan,Miller, Scott J.
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supporting information
p. 602 - 605
(2013/04/11)
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- Benzohydroxamic acids as potent and selective anti-HCV agents
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A diverse collection of 40 derivatives of benzohydroxamic acid (BHAs) of various structural groups were synthesized and tested against hepatitis C virus (HCV) in full-genome replicon assay. Some of these compounds demonstrated an exceptional activity, suppressing viral replication at sub-micromolar concentrations. The compounds were inactive against key viral enzymes NS3, and NS5B in vitro assays, suggesting host cell inhibition target(s). The testing results were consistent with metal coordination by the BHAs hydroxamic group in complex with a target(s). Remarkably, this class of compounds did not suppress poliomyelitis virus (PV) propagation in RD cells indicating a specific antiviral activity of BHAs against HCV.
- Kozlov, Maxim V.,Kleymenova, Alla A.,Romanova, Lyudmila I.,Konduktorov, Konstantin A.,Smirnova, Olga A.,Prasolov, Vladimir S.,Kochetkov, Sergey N.
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supporting information
p. 5936 - 5940
(2013/10/22)
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- An efficient method for the preparation of hydroxamic acids
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Reactions of acyl chlorides with hydroxylamine hydrochloride and NaHCO 3 generate the corresponding hydroxamic acid products in ethyl acetate and water at room temperature for 5 min. This is a simple and efficient method to synthesize a wide range of hydroxamic acids from carboxylic acids in excellent yield and high purity after simple post-treatment without chromatographic purification. In this process, the highlights are the simple separation of products and cheaply available reagents.
- Gao, Xi-Ai,Wang, Xian-Xue,Yan, Hao,Li, Jian,Yan, Ru-Long,Huang, Guo-Sheng
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p. 381 - 385
(2013/05/22)
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- Introducing catalytic lossen rearrangements: Sustainable access to carbamates and amines
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A new, highly efficient and environmentally benign catalytic variant of the Lossen rearrangement is described. Dimethyl carbonate (DMC) as green activation reagent of hydroxamic acids in presence of catalytic amounts of tertiary amine bases {1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-biazabicyclo 5.4.0 undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), and triethylamine} and small quantities of methanol initiate the rearrangement. Methyl carbamates were obtained in good to moderate yields when aliphatic hydroxamic acids were employed in this catalytic Lossen rearrangement; under the same conditions aromatic hydroxamic acids yielded anilines. Notably, the mixture of DMC/methanol was recycled several times without observing decreased yields, thus minimizing the produced waste. Moreover, several other organic carbonates were successfully employed in the introduced catalytic Lossen rearrangement procedure. Copyright
- Kreye, Oliver,Wald, Sarah,Meier, Michael A. R.
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supporting information
p. 81 - 86
(2013/03/13)
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- A convenient one-pot synthesis of aryl amines from aryl aldoximes mediated by Koser's reagent
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A simple and convenient procedure has been developed for the synthesis of aromatic amine by a one-pot reaction of aromatic aldoxime with hypervalent iodine(III) reagent [hydroxy(tosyloxy)iodo]benzene (HTIB, Koser's reagent), in an alkaline medium. The aldoxime reacts with Koser's reagent to form an intermediate hydroxamic acid, which then undergoes Lossen type rearrangement to produce the desired amine. Several amines have been prepared which otherwise are difficult to prepare, by the reduction of corresponding nitro compounds. The scopes and limitations of this transformation have been discussed. ARKAT-USA, Inc.
- Ghosh, Harisadhan,Baneerjee, Arghya,Rout, Saroj Kumar,Patel, Bhisma K.
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experimental part
p. 209 - 216
(2011/05/30)
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- Base-mediated rearrangement of free aromatic hydroxamic acids (ArCO-NHOH) to anilines
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Without using activating agents, a variety of free aromatic hydroxamic acids could be rearranged to aromatic amines in the presence of base alone. The Royal Society of Chemistry 2009.
- Hoshino, Yujiro,Okuno, Moriaki,Kawamura, Eri,Honda, Kiyoshi,Inoue, Seiichi
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supporting information; experimental part
p. 2281 - 2283
(2009/09/06)
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- Carbonyldiimidazole-mediated lossen rearrangement
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[Chemical Equation Presented] Carbonyldiimidazole (CDI) was found to mediate the Lossen rearrangement of various hydroxamic acids to isocyanates. This process is experimentally simple and mild, with imidazole and CO 2 being the sole stoichiometric byproduct. Significant for large-scale application, the method avoids the use of hazardous reagents and thus represents a green alternative to standard processing conditions for the Curtius and Hofmann rearrangements.
- Dube, Pascal,Fine Nathel, Noah F.,Vetelino, Michael,Couturier, Michel,Aboussafy, Claude Larrivee,Pichette, Simon,Jorgensen, Matthew L.,Hardink, Mark
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supporting information; body text
p. 5622 - 5625
(2010/03/02)
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- Determination of pKa's of hydroxamic acids by nucleophilic substitution reaction
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Acid dissociation constant (pKa) of some para-substituted benzohydroxamic, 4-XC6H4CONHOH, and N-methyl para-substituted benzohydroxamic acids, 4- XC6H4CON(OH) CH3, where X = H, CH3, CH3O, NO2, Cl, have been determined spectrophotometrically by nucleophilic substitution reactions of p-nitrophenyl acetate with hydroxamate ions at 27± 0.1°C. All reactions in this study follow pseudo-first order kinetics under condition of excess nucleophile. Good correlation has been observed between pKa and substitutent constants pointing out the validity of the Hammett equation. The kinetics results have been discussed on the basis of pKa and α-effect of hydroxamic acids.
- Shrivastava, Ashish,Ghosh, Kallol K.,Dubey
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p. 1630 - 1634
(2008/09/19)
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- New C-3′ hydroxamate-substituted and more lipophilic cyclic hydroxamate cephalosporin derivatives as a potential new generation of selective antimicrobial agents
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Syntheses of a series of new C-3′ hydroxamate-substituted cephalosporin derivatives with potent antibacterial and media-dependent anti-TB activity are described. The Royal Society of Chemistry 2006.
- Miller, Marvin J.,Zhao, Gaiying,Vakulenko, Sergei,Franzblau, Scott,Moellmann, Ute
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p. 4178 - 4185
(2008/09/20)
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- Hydroxamic acid and its derivatives as inhibitors of melanocyte tyrosinase for topical skin lighteners
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Methods, compounds, and formulations are provided to reduce pigmentation in mammalian skin, comprising hydroxamic acid and its derivatives, and especially benzohydroxamic acid and its derivatives. The compounds preferably inhibit pigment synthesis in melanocytes through inhibition of melanocyte tyrosinase. The methods can be used for lightening skin, and for treating uneven skin complexions, which result from hyperpigmentation-related medical conditions such as melasma, age spots, freckles, ochronosis, and lentigo. The compounds can be used medically or cosmetically, and preferably as topical formulations.
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- Linear free-energy relationships in the protonation equilibria and acid-base catalysed reaction of 4-substituted benzohydroxamic acids
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As part of our investigations on the structure-reactivity relationships in protonation and hydrolysis of hydroxamic acids, we have now studied a series of 4-substituted benzohydroxamic acids (4-X-C6H4.CO.NH(OH), with X=H, Me, OMe, Cl, Br, F and NO2) in aqueous sulfuric acid. Good correlation was observed pointing out the validity of the Hammett equation. The protonation constant, ionization constant and rate constant for acid- and base-catalysed hydrolysis reactions seems are to be related in a linear free-energy (LEER) fashion.
- Ghosh, Kallol K.,Tamrakar, Pankaj
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p. 1153 - 1168
(2007/10/03)
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- 5,5-Dimethyl-1,4,2-dioxazoles as versatile aprotic hydroxamic acid protecting groups
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5,5-Dimethyl-1,4,2-dioxazoles are readily installed by transketalization of 2,2-diethoxypropane, where both the NH and OH moieties are protected in a nonprotic form. The dioxazoles are stable to a wide variety of reaction conditions and readily revert back to the hydroxamic acid by treatment with Nafion-H in 2-propanol. The method is applicable to primary, secondary, tertiary, and aromatic hydroxamic acids, and the acidity of the protons adjacent to the dioxazole allows α-functionalization.
- Couturier, Michel,Tucker, John L.,Proulx, Caroline,Boucher, Ghislain,Dube, Pascal,Andresen, Brian M.,Ghosh, Arun
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p. 4833 - 4838
(2007/10/03)
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- A convenient method for the preparation of hydroxamic acids
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A one-step conversion of carboxylic acid to hydroxamic acid, under neutral pH conditions is described. This simple, selective and efficient method was applied to a wide range of aliphatic/aromatic carboxylic acid derivatives that contain hydroxyl, halo, ester and other base sensitive groups as substituents. The method utilizes cheaply available reagents and hence it is a practical and cost effective strategy, compared to the other methods available in the literature. (C) 2000 Elsevier Science Ltd.
- Reddy,Kumar,Reddy
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p. 6285 - 6288
(2007/10/03)
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- Solid supported synthesis of hydroxamic acids
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A novel approach to the solid supported synthesis of hydroxamic acids was developed. It employs oxime resin and unlike all previously reported methods allows for the use of acid labile protecting groups. Cleavage is induced by treatment with tert-butyldim
- Golebiowski, Adam,Klopfenstein, Sean
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p. 3397 - 3400
(2007/10/03)
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- An unusual ground-state stabilization effect and origins of the α- effect in aminolyses of Y-substituted phenyl X-substituted benzoates
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Second-order rate constants have been measured spectrophotometrically for the reactions of X-C6H4CO2C6H4-Y with a series of primary amines in H2O containing 20 mol% DMSO at 25.0 ± 0.1°C. The reactivity increases as the substituent (X and Y) becomes a stronger electron-withdrawing group. The σ+ constants give better Hammett correlation than σ constants for the reactions of 4-nitrophenyl X-substituted benzoates with glycylglycine (glygly) and hydrazine (NH2NH2), indicating that the ground-state stabilization effect is unusually significant on the reaction rates. The reactions of X-C6H4CO2C6H4-Y with glygly and NH2NH2 appear to proceed through the same mechanism, but the degree of leaving-group departure and the negative charge developed in the acyl moiety at the rate-determining TS is considered to be more significant for the glygly system than the NH2NH2 system based on β(1g) and ρ(x) values. The magnitude of the α-effect is observed to be not always dependent on the β(nuc) value but dependent on the electronic nature of the substituent X and Y, i.e., an electron-donating substituent increases the α-effect, while an electron-withdrawing one decreases the α-effect. The present study has led to the conclusion that the ground-state effect is important for the reaction rates but it is not solely responsible for the α-effect, and the intramolecular H-bonding interactions (4) are proposed for the cause of the increasing or decreasing α-effect trends observed in the present system.
- Um, Ik-Hwan,Chung, Eun-Kyung,Lee, So-Mi
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p. 729 - 737
(2007/10/03)
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- SYNTHESIS AND STRUCTURE OF HYDROXYISOXAZOLIDINES AND DERIVATIVES OF HYDROXYLAMINE AND ALKENALS
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The reactions of N-substituted hydroxylamines with alkenals serve as a method for the synthesis of the corresponding 2-substituted 3(5)-hydroxyisoxazolidines.The reaction pathway is determined by the nature of the substituent attached to the nitrogen atom.Ring-chain isomerism has been detected in these newly obtained compounds.
- Zelenin, K. N.,Motorina, I. A.,Sviridova, L. A.,Bezhan, I. P.,Ershov, A. Yu.,et al.
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p. 1018 - 1024
(2007/10/02)
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