- Stereoselective cycloaddition of nitrile oxides to a dispiroketal-protected but-3-ene-1,2-diol
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The influence of a dispiroketal protecting group on the π-facial selectivity of nitrile oxide cycloaddition of S-but-3-ene-1,2-diol has been investigated. Ethoxycarbonylformonitrile oxide and benzonitrile oxide undergo regiospecific and diasteroeselective addition to alkene 7 to afford isoxazolines 11 and 12. The major adducts (11a and 11b) are formed with 44% and 50% d.e. respectively, and in each case have S-configuration at C-5, the new stereogenic centre.
- Gravestock,Paton,Todd
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Read Online
- Synthesis of Biologically Active Heterospirocycles through Iterative 1,3-Dipolar Cycloaddition Pathways
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We demonstrate the novel spiroannulation of exo-imines with 1,3-dipoles, for the first time, leading to 3D spirocycles with a secondary amine (NH) in the spiro-ring. The synthetic method described herein allows access to these previously unexplored heterospirocyclic cores that have application in the discovery of functional molecules for medicinal and materials science. This was demonstrated by discovering an unprecedented class of heterospirocycles with antimalarial activity against the human protozoan P. falciparum.
- Sharma, Pallavi,Ranga Prabhath,Wong, Derek,Ampem-Lassen, Maame Adjoa,Bhat, Shreesha V.,Williams, Luke,Carvalho, Teresa G.
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Read Online
- Oxidation of: O -dioxime by (diacetoxyiodo)benzene: Green and mild access to furoxans
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Furoxan has been widely used in the field of high energy density materials because of its excellent properties such as high density, high standard enthalpy of formation and high nitrogen content. However, its existing synthesis methods are still restricted by the problems of difficult substrate preparation and manual handling of hazardous reagents. Herein, we disclosed a mild oxidation strategy to efficiently obtain furoxan derivatives starting from readily available o-dioxime substrates. This reaction features high functional group tolerance and easy scale-up, and has excellent regioselectivity for specific nonsymmetric o-dioximes. This method greatly reduces the safety risk and simplifies the operation process, and means that diversified furoxan derivatives can be easily accessed, thus paving the way for the wide application of furoxan derivatives. This journal is
- He, Chunlin,Pang, Siping,Zhang, Qi,Zhang, Xun,Zhao, Cheng
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supporting information
p. 1489 - 1493
(2022/01/31)
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- Synthesis method of furoxan compound
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The invention discloses a synthesis method of a furazan oxide compound. The synthesis method comprises the following step of: oxidizing a glyoxime compound by taking iodobenzene diethyl ester as an oxidizing agent to carry out a reaction to obtain the fur
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Paragraph 0045-0052
(2021/01/04)
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- Electrocyclic Ring-Opening of 1,2,4-Oxadiazole[4,5-a]piridinium Chloride: a New Route to 1,2,4-Oxadiazole Dienamino Compounds
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1,2,4-Oxadiazole[4,5-a]piridinium chloride adds nucleophiles to undergo electrocyclic ring opening affording 1,2,4-oxadiazole dienamino derivatives. These pyridinium salts represent a special class of Zincke salts that are prone to rearrange when treated
- Carella, Stefano,Memeo, Misal Giuseppe,Quadrelli, Paolo
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p. 1209 - 1221
(2019/10/19)
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- Heterocyclization of 5-(Arylmethylidene)pyrimidine-2,4,6(1H,3H,5H)-triones with Arenecarbaldehyde Oximes in the Presence of N-Bromosuccinimide and Triethylamine
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5-(Arylmethylidene)pyrimidine-2,4,6(1H,3H,5H)-triones reacted with substituted benzaldehyde oximes in the presence of N-bromosuccinimide and triethylamine to give 1,4-diaryl-2-oxa-3,7,9-triazaspiro-[4.5]dec-3-ene-6,8,10-triones and 3,4-diaryl-1,2,5-oxadia
- Tyrkov,Yurtaeva
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p. 978 - 982
(2019/09/06)
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- tert-Butyl Nitrite Mediated Different Functionalizations of Internal Alkenes: Paths to Furoxans and Nitroalkenes
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tert-Butyl nitrite (TBN) reacts differently with various internal alkenes leading to interesting and useful products. Synthesis of 1,2,5-oxadiazole-N-oxides (furoxans) has been achieved from internal alkenes using tert-butyl nitrite (TBN), quinoline and K2S2O8. Under an identical reaction condition α,β-unsaturated carboxylic acids and cyclic and acyclic internal alkenes both afforded nitroalkenes as the sole product via decarboxylative and direct nitration path respectively. (Figure presented.).
- Mir, Bilal Ahmad,Singh, Sarangthem Joychandra,Kumar, Ritush,Patel, Bhisma K.
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p. 3801 - 3809
(2018/09/18)
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- Green approach for the synthesis of thiophenyl pyrazoles and isoxazoles by adopting 1,3-dipolar cycloaddition methodology and their antimicrobial activity
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A variety of N-((1,3-diphenyl-5-aryl-1H-pyrazol-4-yl)sulfonyl)thiophene-2-carboxamides (7) and N-((5-aryl-3-phenylisoxazol-4-yl)sulfonyl)thiophene-2-carboxamides (8) were prepared from (E)-N-(arylethenesulfonyl)thiophene-2-carboxamides (4) adopting 1,3-di
- Sowmya,Lakshmi Teja,Padmaja,Kamala Prasad,Padmavathi
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p. 891 - 898
(2017/12/26)
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- Synthesis of Furoxans (1,2,5-oxadiazole 2-oxides) from Styrenes and Nitrosonium Tetrafluoroborate in Non-Acidic Media and Mechanistic Study
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Diverse furoxans (1,2,5-oxadiazole 2-oxides) were synthesized from the corresponding styrenes using nitrosonium tetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid-sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism.
- Matsubara, Ryosuke,Ando, Akihiro,Saeki, Yuta,Eda, Kazuo,Asada, Naoki,Tsutsumi, Tomoaki,Shin, Yong Soon,Hayashi, Masahiko
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p. 1094 - 1105
(2016/07/29)
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- An Efficient Scale-Up Synthesis of BMS-520, a Potent and Selective Isoxazole-Containing S1P1 Receptor Agonist
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This article reports an efficient scale-up synthesis of 1-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)benzyl)azetidine-3-carboxylic acid (BMS-520), a potent and selective isoxazole-containing S1P1 receptor agonist. Th
- Hou, Xiaoping,Zhu, Juliang,Chen, Bang-Chi,Watterson, Scott H.,Pitts, William J.,Dyckman, Alaric J.,Carter, Percy H.,Mathur, Arvind,Zhang, Huiping
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p. 989 - 995
(2016/06/09)
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- Synthesis of furoxans from styrenes under basic or neutral conditions
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Furoxans (1,2,5-oxadiazole 2-oxides) can be synthesized from the corresponding styrenes using NOBF4 under basic or even almost neutral reaction conditions. Acid-sensitive functional groups are tolerated under the developed basic conditions. For
- Matsubara, Ryosuke,Saeki, Yuta,Li, Jianhua,Eda, Kazuo
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p. 1524 - 1528
(2013/07/05)
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- An improved synthesis of 1,2-benzisoxazoles: TBAF mediated 1,3-dipolar cycloaddition of nitrile oxides and benzyne
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An efficient synthesis of a range of 1,2-benzisoxazoles using an improved 1,3-dipolar cycloaddition of nitrile oxides and benzyne is described. Key to the procedure is the in situ generation of the reactive nitrile oxide and benzyne reaction partners medi
- Spiteri, Christian,Sharma, Pallavi,Zhang, Fengzhi,MacDonald, Simon J. F.,Keeling, Steve,Moses, John E.
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supporting information; experimental part
p. 1272 - 1274
(2010/07/05)
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- Magtrieve (CrO2) and MnO2 mediated oxidation of aldoximes: Studying the reaction course
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Magtrieve (CrO2) and MnO2 mediated oxidation of aldoximes to nitrile oxides were studied in details. In presence of external radical source, TEMPO, these reagents did not furnish nitrile oxides, instead favoured deoximation to aldehydes. A common trend of deoximation was established from electronically tuned aldoximes, which is: aliphatic>aromatic> aldoximes with strong electron-withdrawing group, though the extent of deoximation was less in case of CrO2. Above effects were not observed with chloramine-T and diacetoxyiodobenzene, reagents known to produce nitrile oxides via hydroximoyl halide or equivalent ionic intermediates. A putative reaction mechanism is proposed for MO2 (M=Cr, Mn) mediated oxidation of aldoximes through formation of a nitroso-oxime tautomeric pair. Formation of nitrile oxide is possibly occurred from the oxime tautomer via a σ-type iminoxy radical intermediate. The deoximation process, dominating in presence of external radical environment, is explained following decomposition of the nitroso tautomer.
- Bhosale, Sandeep,Kurhade, Santosh,Vyas, Samir,Palle, Venkata P.,Bhuniya, Debnath
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scheme or table
p. 9582 - 9588
(2011/01/03)
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- Copper(II)-mediated oxidation of 1,2-dioxime to furoxan
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1,2-Dioximes undergo oxidative transformation mediated by copper(II) ions in acetonitrile to form the corresponding furoxans in high yields. A series of 1,2-dioximes including aliphatic, aromatic, and heterocyclic dioximes were oxidized using these mild c
- Das, Oindrila,Paria, Sayantan,Paine, Tapan Kanti
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experimental part
p. 5924 - 5927
(2009/04/05)
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- Studies of nitrile oxide cycloadditions, and the phenolic oxidative coupling of vanillin aldoxime by Geobacillus sp. DDS012 from Italian rye grass silage
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During studies directed towards the discovery of nitrile hydrolysing enzymes from thermophiles, vanillin aldoxime was incubated with the thermophilic organism, Geobacillus sp. DDS012 isolated from Italian rye grass (Lolium multiflorum) silage. The predominant product was a dihydro-dimer, which could only be characterised by LC-MS. This was initially imagined to be the product of cycloaddition of vanillin aldoxime with the corresponding nitrile oxide, but preparation of the supposed adduct and model studies excluded this possibility. The rate constant for the second order dimerisation of 4-O-acetyl vanillin nitrile oxide was measured (1.21 × 10-4 M-1 s -1, 0.413 M, 25 °C) and the 13C-NMR signal for the nitrile oxide carbon was observed (δC 34.4, br. t 1J13C,14N circa 50 Hz). Treatment of vanillin aldoxime with potassium persulfate and iron sulfate gave material with the same LC-MS properties as the natural product, which is therefore identified as 5,5′-dehydro-di-(vanillin aldoxime) 1d formed by phenolic oxidative coupling. This journal is The Royal Society of Chemistry.
- Kelly, David R.,Baker, Simon C.,King, David S.,De Silva, Deepa S.,Lord, Gwyn,Taylor, Jason P.
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p. XX787-796
(2008/09/17)
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- An efficient one-step regiospecific synthesis of novel isoxazolines and isoxazoles of N-substituted saccharin derivatives through solvent-free microwave-assisted [3+2] cycloaddition
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Novel isoxazolines and isoxazoles of N-substituted saccharin derivatives are synthesized in good yields by 1,3-dipolar cycloaddition of N-allyl or propargyl N-substituted saccharin with arylnitrile oxide under solvent-free microwave irradiation. In this process, the yields were significantly improved over conventional heating, without alteration of the selectivity. The regioselectivity as well as the nonthermal specific microwave effect are discussed.
- Mabrour, Mahmoud,Bougrin, Khalid,Benhida, Rachid,Loupy, André,Soufiaoui, Mohamed
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p. 443 - 447
(2008/02/04)
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- Synthesis and biological evaluation of 3,4-diphenyl-1,2,5-oxadiazole-2- oxides and 3,4-diphenyl-1,2,5-oxadiazoles as potential hybrid COX-2 inhibitor/nitric oxide donor agents
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A group of 3,4-diphenyl-1,2,5-oxadiazole-2-oxides (3,4-diphenylfuroxans) and the corresponding N-desoxy 3,4-diphenyl-1,2,5-oxadiazoles (3,4-diphenylfurazans) analogs, were synthesized for in vitro evaluation as hybrid cyclooxygenase (COX) inhibitor/nitric
- Velazquez, Carlos,Rao, P.N. Praveen,McDonald, Robert,Knaus, Edward E.
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p. 2749 - 2757
(2007/10/03)
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- 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides to Prop-1-ene-1,3-sultone
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The reaction of prop-1-ene-1,3-sultone 1 with a variety of nitrile oxides 3 afforded novel [3+2] cycloaddition products 4 in good yield. The cycloaddition reaction achieved excellent regioselectivity.
- Tian, Li,Xu, Guo-Yan,Ye, Yong,Liu, Lun-Zu
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p. 1071 - 1074
(2007/10/03)
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- Precipitons - Functional protecting groups to facilitate product separation: Applications in isoxazoline synthesis
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Imagine - After a homogeneous reaction is complete, the chemist adds a catalyst or exposes the reaction mixture to soft UV light and pure product precipitates from the reaction mixture. This can be achieved with "precipitons" - Protecting groups that have controllable solubility states. The first advances towards that goal are described (see scheme).
- Bosanac, Todd,Yang, Jaemoon,Wilcox, Craig S.
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p. 1875 - 1879
(2007/10/03)
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- Generation of nitrile oxides from oxime derivatives by the oxidation with ammonium hexanitratocerate(IV)
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Aromatic and aliphatic nitrile oxides are generated by the oxidation of α-hydroxyimino carboxylic acid with ammonium hexanitratocerate(IV). They react with olefinic and acetylenic dipolarophiles to give the corresponding cycloaddition products in good yield. The oxidation of α-oxo aldoximes also affords α-oxo carbonitrile oxides.
- Arai, Noriyoshi,Iwakoshi, Mitsuhiko,Tanabe, Katsuhiko,Narasaka, Koichi
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p. 2277 - 2285
(2007/10/03)
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- Cycloadditions of nitrile oxides to amidoximes. A general synthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides
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The cycloaddition of nitrile oxides to amidoximes is a general method for the synthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides with the same or different substituents. The yields are only moderate since an equivalent amount of the nitrile oxide is consumed by reaction with the amine released in the fragmentation of the primary cycloadducts and reforms the amidoxime. With excess nitrile oxides the 1,2,4-oxadiazole-4-oxides undergo a disproportionation reaction to yield nitroso carbonyl intermediates and 1,2,4-oxadiazoles.
- Quadrelli, Paolo,Invernizzi, Anna Gamba,Falzoni, Mario,Caramella, Pierluigi
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p. 1787 - 1796
(2007/10/03)
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- Cycloaddition of benzonitrile oxide to pyridazine, pyrimidine and pyrazine
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Cycloaddition of benzonitrile oxide to pyridazine affords an isolable mono-cycloadduct. In cycloadditions to pyrimidine and pyrazine the primary mono-cycloadducts are labile intermediates which undergo further cycloaddition affording isolable bis- and tris-cycloadducts.
- Corsaro, Antonino,Perrini, Giancarlo,Pistara, Venerando,Quadrelli, Paolo,Gamba Invernizzi, Anna,Caramella, Pierluigi
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p. 6421 - 6436
(2007/10/03)
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- Cycloadditions of Nitrile Oxides and Nitrones to 4,4-Methylene-1-methylpiperidine: Studies in Regio- and Stereoselectivity
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A series of spiro-substituted isoxazole derivatives were synthesized by 1,3-dipolar cycloadditions of nitrile oxides and nitrones to 4,4-methylene-1-methylpiperidine.Since nmr studies confirmed that only one regioisomer was formed selectively, semi-empirical quantum mechanical methods (AM1) were used to rationalize this regiochemical preference via calculation and inspection of HOMO-LUMO-energy and coefficients.X-ray structure analysis carried out for one of these products showed the occurrence of only one stereoisomer, explicable by comparing AM1-calculated ΔHf-values of all possible cycloadducts. - Keywords: 1,3-Dipolar cycloaddition; Nitrile oxide; Nitrone; 4,4-Methylene-1-methylpiperidine; AM1 calculations.
- Fisera, L.,Sauter, F.,Froehlich, J.,Feng, Y.,Ertl, P.,Mereiter, K.
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p. 553 - 564
(2007/10/02)
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- ?-FACIAL SELECTIVITY IN THE CYCLOADDITION OF NITRILE OXIDES TO 5,6-DIDEOXY-5-ENOFURANOSES
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Benzonitrile oxide and ethoxycarbonylformonitrile oxide cycloadd regiospecifically and diastereoselectively to α-methyl 5,6-dideoxy-2,3-O-isopropylidene-Δ-lyxo-hex-5-enofuranoside 7 to afford isoxazolines 10 and 11.The ?-facial selectivity (ca. 7:1) is co
- Blake, Alexander J.,Kirkpatrick, Graeme,McGhie, Karen E.,Paton, R. Michael,Penman, Kenneth J.
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p. 409 - 420
(2007/10/02)
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- Reaction of N-Unsubstituted Imidazoles with Benzonitrile Oxide
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The behaviour of N-unsubstituted imidazoles 1 with benzonitrile oxide is reported.The results indicate that in solution a ring-chain tautomerism exists between the cycloadduct 3B and the Z-oxime 3A; while in the solid state only the chain form 3A was observed.Oximes of N-benzoylimidazol-2-ones 4, derived from subsequent attack of the 1,3-dipole on both tautomers, and 3,6-diphenyl-1,4,2,5-dioxadiazine 2, an unusual dimer of the benzonitrle oxide, were also isolated.A mechanism involving a zwitterionic intermediate is proposed.The structure of the oximes of N-benzoylimidazol-2-one 4 and 10, derived from benzonitrle oxide and p-toluonitrile oxide respectively, was determined by X-ray diffraction analysis.
- Grassi, Giovanni,Foti, Francesco,Risitano, Francesco,Bruno, Giuseppe,Nicolo, Francesco,Munno, Giovanni De
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p. 2615 - 2620
(2007/10/02)
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- Stereoselective Cycloaddition of Nitrile Oxides to 6,7-Dideoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-hept-6-enopyranose
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Ethoxycarbonylformonitrile oxide and benzonitrile oxide cycloadd regiospecifically and stereoselectively to the D-galactose derived alkene 3 to afford isoxazolines 4 and 5.The major adducts (4a and 4b) are formed with 82percent and 74percent d.e. respecti
- Blake, Alexander J.,Gould, Robert O.,Paton, R. Michael,Young, Anne A.
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p. 3173 - 3190
(2007/10/02)
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- New aspects of nitrile oxides chemistry
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Reactivity of nitrile oxides (1) towards both dimerization and cycloaddition with dipolarophiles can be inhibited by catalytic amount of tris-(4-bromophenyl)-aminium hexachloroantimonate and subsequently restored.
- Auricchio, Sergio,Ricca, Aldo,Romeo, G. Battista,Truscello, Ada M.
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p. 4363 - 4364
(2007/10/02)
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- Regio- and Face-selective Cycloaddition of Benzonitrile Oxide and C,N-Diphenylnitrone to 6,8-Dioxabicyclooct-3-ene
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Benzonitrile oxide, generated by dehydrochlorination of benzohydroximoyl chloride, undergoes regio- and face-selective cycloaddition to 6,8-dioxabicyclooct-3-ene 5 yielding a 4:1 mixture of 4,5-dihydroisoxazoles 6 and 7.Both products have exo-stereochemistry resulting from approach of the nitrile oxide from the face opposite the methyleneoxy bridge.The structures of the adducts were determined by 1H NMR spectroscopy and, in the case of compound 6, by X-ray crystallography.The corresponding reaction with C,N-diphenylnitrone yielded three of the eight possible isoxazolidines, the major isomer being exo,endo-adduct 16.
- Blake, Alexander J.,Dawson, Ian M.,Forsyth, Angus C.,Gould, Robert O.,Paton, R. Michael,Taylor, Desmond
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- Iodobenzene dichloride - An efficient reagent for preparation of nitrile oxides from aldoximes
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Reaction of aldoximes with iodobenzene dichloride leads to formation of corresponding nitrile oxides in good yields in a single pot reaction.
- Radhakrishna,Sivaprakash,Singh
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p. 1625 - 1629
(2007/10/02)
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- Regioselective synthesis of C-nucleosides by 1,3-dipolar cycloaddition of arylnitrile oxides to 5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hex-5-enofuranose
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The synthesis of 3-aryl-5-(1,2-O-isopropylidene-α-D-xylo-tetrofuranos-4-yl)-2-isoxazoline (3) from arylnitrile oxides and 5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hex-5-enofuranose (1) is described.The 1,3-dipolar cycloaddition reactions give mainly anti-adducts (>=95percent ?-facial stereoselectivity).
- Al-Timari, Usama A. R.,Fisera, Lubor
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p. 121 - 127
(2007/10/02)
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- Cycloaddition of nitrile oxides to 3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-α-D-ribo-hex-5-enofuranose
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Benzonitrile oxide and ethoxycarbonylformonitrile oxide cyclo-added to the title compound to afford a mixture of 3-substituted (phenyl or ethoxycarbonyl)(5R)- (6) and (5S)-5-(3-O-benzyl-1,2-O-isopropylidene-α-D-ribo-tetrofuranos-4-yl)-2-isoxazoline (7).Th
- Blake, Alexander J.,Gould, Robert O.,McGhie, Karen E.,Paton, R. Michael,Reed, David,et al.
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p. 461 - 474
(2007/10/02)
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- ANODIC ELECTROLYSIS OF KETOXIMES AND ALDOXIMES: MECHANISM
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The key step in the electrochemical oxidation of ketoximes which determines the composition of the electrolysis products is the reaction of the intermediate oxoimmonium cation with the original oxime, whereas in the case of aldoximes, the key step is dimerization of the iminoxy radicals.
- Petrosyan, V. A.,Niyazymbetov, M. E.,Ul'yanova, E. V.
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p. 546 - 550
(2007/10/02)
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- ELECTROCHEMICAL OXIDATION OF VICINAL DIOXIMES
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First-wave oxidation of vicinal dioximes corresponds to the transfer of two electrons and two protons to give furoxans, which are further oxidized at the potentials of the second wave.It is shown that the key step in the electrochemical cylization of vici
- Niyazymbetov, M. E.,Ul'yanova, E. V.,Petrosyan, V. A.
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p. 551 - 554
(2007/10/02)
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- ADDITION OF PICOLINES TO BENZONITRILE OXIDE. A DIVERGING PATH WITH 4-PICOLINE
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Biscycloadducts are formed by exposing 2- and 3-picoline to benzonitrile oxide. 4-picoline instead affords products of condensation on the methyl group.
- Albini, Franca Marinone,Franco, Rita De,Bandiera, Tiziano,Gruenager, Paolo,Caramella, Pierluigi
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- REACTIONS OF NITRILE OXIDES WITH NITROGEN OXIDES. 2. REACTIONS WITH NITROGEN MONOXIDE AND NITROGEN SESQUIOXIDE
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We have studied the reactions of aromatic nitrile oxides with nitrogen monoxide and nitrogen sesquioxide.It was shown that the nitrogen monoxide removes an oxygen atom from the nitrile oxide with formation of the corresponding nitrile and nitrogen dioxide.The reaction products with nitrogen sesquioxide are formed as a result of reactions of the nitrile oxide with nitrogen monoxide and nitrogen tetroxide.
- Rakitin, O. A.,Ogurtsov, V. A.,Godovikova, T. I.,Khmel'nitskii, L. I.
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p. 1472 - 1474
(2007/10/02)
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- A Convenient Synthesis of Nitrile Oxides from Aldoximes by 1-Chlorobenzotriazole
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Nitrile oxides can be conveniently prepared from aldoximes utilizing 1-chlorobenzotriazole in dichloromethane.The reaction and work-up procedures are simple and the isolated yields high.
- Kim, Jae Nyoung,Ryu, Eung K.
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p. 1373 - 1377
(2007/10/02)
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- Nucleophile and Nucleofuge Effects, Catalysis, and Stereochemistry in Vinylic Substitution of Electrophilic Nitro Olefins
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The substitution of (E)- and (Z)-β-iodo-α-nitrostilbenes (E-3-I and Z-3-I) and of the (E)-β-chloro (E-3-Cl) and of (E)-β-nitro (E-3-NO2) analogues with several nucleophiles were studied in MeCN and EtOH.Amine catalysis in the substitution with morpholine
- Rappoport, Zvi,Topol, Alain
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p. 5967 - 5977
(2007/10/02)
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- Isoxazolinyldioxepins. Part 1. Structure-Reactivity Studies of the Hydrolysis of Oxazolinyldioxepin Derivatives
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The preparation and acid catalyzed hydrolysis of a number of isoxazolinyldioxepins is reported.Individual diastereoisomer pairs were isolated by column chromatography and shown to differ significantly in their hydrolytic stability at acidic pH.The crystal structures of one diastereoisomer pair reveal that conformational differences induce a selective stereoelectronic effect at the acetal centre of the more hydrolytically labile isomer, while the less labile isomer shows no such selectivity.
- Camilleri, Patrick,Munro, David,Weaver, Karen,Williams, David J.,Rzepa, Henry S.,Slawin, Alexandra M. Z.
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p. 1929 - 1934
(2007/10/02)
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- Mechanistic Impact of Oxime Formation Accompanying 1,3-Dipolar Cycloadditions of Nitrile Oxides
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Benzonitrile oxide (1a) reacts with 1,1,2,2,3,3-hexamethyl-4,5-bis(methylene)cyclopentane (5) to give a mixture of the 1,3-dipolar cycloaddition product 8 and the oxime 9.This reaction is 26 times slower than the corresponding reaction of 1a with 1,2-bis(
- Baran, Janusz,Mayr, Herbert
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p. 5012 - 5016
(2007/10/02)
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- Regio- and Face-selective Formation of 1:1 and 2:1 Adducts by 1,3-Dipolar Cycloaddition of Benzonitrile Oxide to 2-Alkoxy-5,6-dihydro -2H-pyrans
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Benzonitrile oxide, generated by dehydrochlorination of benzohydroximoyl chloride, reacts with 2-methoxy-5,6-dihydro-2H-pyran (1:6) to afford three isomeric isoxazolines (2a), (3a), and (4a), together with diphenylfurazan N-oxide and 3,5-diphenyl-1,2,4-oxadiazole as by-products.The structures of the adducts were determined by 1H n.m.r. spectroscopy and, in the case of compound (2a), by X-ray crystallography.Compounds (2a)-(4a) are formed in the ratio 5.7:2.4:1.0, corresponding to 8:1 face selectivity due to approach of the benzonitrile oxide anti to the 2-methoxy substituent, and to ca. 3:1 regioselective formation of isomers with the carbon of the 1,3-dipole attached to pyran C(3).Under similar conditions 2-(t-butoxy)-5,6-dihydro-2H-pyran yields only two of the four possible adducts: (2b) and (3b), both resulting from antiface attack.The use of 1:1 molar ratio of hydroximoyl chloride and alkene afforded 2:1 adducts (8), (9), and (10), in addition to 1:1 products (2a)-(4a).X-ray crystallography for diadducts (8) and (10) confirmed that they were formed by cycloaddition of the second benzonitrile oxide to the C=N of the isoxazolines, the 1,3-dipole approaching in each case from the less hindered face.
- Blake, Alexander J.,Dawson, Ian M.,Forsyth, Angus C.,Johnson, Trevor,Paton, R. Michael,et al.
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p. 2548 - 2580
(2007/10/02)
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- Formation of 4-Benzamidoisoxazole Derivatives
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The titled compounds (3) were synthesized by the reaction of nitrile oxides with 1-azirines and also the reaction of aliphatic nitro compounds with dibenzoylmethane derivatives in the presence of acetyl chloride and sodium methoxide.The structure of 3 was
- Zen, Shonosuke,Harada, Kazuho,Nakamura, Hikaru,Iitaka, Yoichi
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p. 2881 - 2884
(2007/10/02)
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- CYCLOADDUCTS OF BENZONITRILE OXIDE TO PYRIDINE. A CASE OF A TWO-STEP CYCLOADDITION
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Pyridine adds benzonitrile oxide in apolar solvents, affording fair yields of bisadducts III and IV.Quinoline and isoquinoline afford isolable monocycloadducts VIII and IX.
- Corsaro, A.,Perrini, G.,Caramella, P.,Albini, F. Marinone,Bandiera, T.
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p. 1517 - 1520
(2007/10/02)
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- A Convinient Preparative Method of Nitrile Oxides by the Dehydration of Primary Nitro Compounds with Ethyl Chloroformate or Benzenesulfonyl Chloride in the Presence of Triethylamine
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Three nitrile oxides (MeOCOCN->O, PhCN->O, and EtCN->O) were effectively generated in situ by dehydration of the corresponding primary nitro compounds (RCH2NO2) with PhSO2Cl or ClCOOEt in the presence of triethylamine.Various cycloadducts were prepared by the reaction of them with dipolarophiles.Some advantages of these methods are described in comparison with other known methods.
- Shimizu, Tomio,Hayashi, Yoshiyuki,Shibafuchi, Hiroshi,Teramura, Kazuhiro
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p. 2827 - 2832
(2007/10/02)
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- Experiments to Synthesize a Formal Nitrile Oxide-Benzene Adduct. 1,3-Dipolar Cycloadditions to Bicyclohex-5-ene-2,3-dicarboxylic Anhydride, Dewar Benzene, and 1,4-Cyclohexadiene
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The reaction of bicyclohex-5-ene-2,3-dicarboxylic anhydride (7) with benzonitrile oxide, 2,4,6-trimethylbenzonitrile oxide, diphenylnitrile imine, diazomethane, tetrachloro-o-quinone, and tetrachlorothiophene 1,1-dioxide furnished the Δ2-isoxazolines 8a, 8b, the Δ2-pyrazoline 8c, the Δ1-pyrazoline 10d, the α-diketone 11, and the tetrachloro-1,3-cyclohexadiene derivative 12, respectively. - Dewar benzene (16) was prepared via the urazole 13, obtained from benzvalene by the addition of 4-methyl-4H-1,2,4-triazole-3,5-dione, and the azo compound 17, from which nitrogen gas eliminated by photolysis.The 1:1 adducts 6a, 6b, 20, and 21 as well as the 1:2 adducts 18a, 18b, 19b, 22, and 23, respectively, were formed on treatment of 16 with benzonitrile oxide, 2,4,6-trimethylbenzonitrile oxide, and diazomethane.At 120 deg C the 1:1 adduct 6b decomposed to give benzene and the 1:2 adducts 18b, 19b, probably via the intermediate 1b, which was the target molecule of this investigation.If the thermolysis was carried out in the presence of dimethyl fumarate, 18b, 19b were no longer observed and the dimethyl Δ2-isoxazoline-3,4-dicarboxylate 24 was obtained instead. - 1,4-Cyclohexadiene reacted with benzonitrile oxide and 2,4,6-trimethylbenzonitrile oxide to provide the 1:1 adducts 25 and the 1:2 adducts 26 - 28.The thermal decomposition of 25b resulted in the formation of mesitylphenylketimine (31).A 3:1 mixture of the dibromides 32 and 33 was obtained on addition of bromine to 25a.Elimination of hydrogen bromide from 32 was effected by diazabicycloundecane with benzene and diphenylfuroxan (35) being the products and the formal benzene adduct 1a the most likely intermediate.Compound 32 was tr ansformed into the spiran 36 by using the stronger base potassium tert-butoxide.
- Christl, Manfred,Mattauch, Brigitte
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p. 4203 - 4223
(2007/10/02)
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- Activation of Nitriles by Hydrogen Bonding in Cycloadditions with Nitrile Oxides
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The dipolarophilic activity of aromatic nitriles in cycloaddition with benzonitrile oxides is remarkably enhanced by ortho-acylamino substituents.The activation depends upon the solvent and can be ascribed to a hydrogen bond which assists cycloaddition.
- Corsaro, Antonino,Chiacchio, Ugo,Caramella, Pierluigi,Purrello, Giovanni
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p. 949 - 952
(2007/10/02)
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- THE REACTION OF TRIPHENYLPHOSPHINE WITH ARYLBROMONITROMETHANES. FORMATION OF ARYLNITRILOXIDES
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Formation of furoxans and Δ2-isoxazolines confirms that arylnitriloxides are intermidiates in the reaction of arylbromonitromethanes with triphenylphosphine.
- Coutouli-Argyropoulou, E.
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p. 2029 - 2030
(2007/10/02)
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- FRAGMENTATION OF NITRILE OXIDES WITH TRIETHYLAMINE
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The formation of 1,2,4-oxadiazoles is frequently observed as a side reaction in cyclo additions with nitrile oxides generated in situ and follows from a fragmentation induced by Et3N.This latter is oxidized to N,N-diethylvinylamine, which is trapped as a cycloadduct.
- Caramella, P.,Corsaro, A.,Compagnini, A.,Albini, Marinone F.
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p. 4377 - 4380
(2007/10/02)
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- Dialkyl (3-Aryl-1,2,4-oxadiazol-5-yl)phosphonates: Synthesis and Thermal Behavior - Evidence for Monomeric Alkyl Metaphosphate
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Dialkyl (3-aryl-1,2,4-oxadiazol-5-yl)phosphonates 6a-h have been obtained by 1,3-dipolar cycloaddition of arenenitrile oxides 5a-f to dialkyl phosphorocyanidates (4a and 4b) in yields ranging between 30percent and 58percent.A standardized method for obtaining cyanidates 4a and 4b has been established.The diethyl thiophosphorocyanidate (4c) is less reactive than 4a and 4b, only the 3-(4'-nitrophenyl) derivative 6i being obtainable.While the IR and NMR spectra of 6a-6i were unexceptional, their UV spectra showed evidence of conjugative interaction in high degrees between the phosphonate and heterocyclic moieties as well as a varying conjugative interaction between the heterocyclic and aryl moieties.The oxadiazoles 6a-h are thermally labile and yield trialkyl phosphates 7 as the only identifiable products.A mechanism based on the intermediacy of monomeric alkyl metaphosphate 11 in the formation of trialkyl phosphate was postulated, and supportive evidence in the form of trapping the metaphosphate with acetophenone has been obtained.
- Das, Sushanta K.,Balasubrahmanyam, S. N.
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p. 4232 - 4236
(2007/10/02)
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