- Substituent effects on 15N and 13C NMR chemical shifts of 3-phenylisoxazoles: A theoretical and spectroscopic study
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The synthesis and assignment of 15N and 13C NMR signals of the isoxazole ring in a series of parasubstituted 3-phenyl derivatives are reported. DFT calculations of 15N and 13C chemical shifts are presented and c
- Schofield, Mark H.,Sorel, Marie-Adele,Manalansan, Ryan J.,Richardson, David P.,Markgraf, J. Hodge
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Read Online
- Synthesis of 3-Vinylisoxazole by a Nitrile Oxide Cycloaddition/Diels-Alder Cycloreversion Pathway
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3-Vinylisoxazole is prepared by a sequence involving cycloaddition of acrylonitrile oxide, generated by dehydration of 1-nitropropene, to norbornadiene followed by Diels-Alder cycloreversion of the resulting 2-isoxazoline under flash vacuum pyrolysis cond
- Ambler, Philip W.,Paton, R. Michael,Tout, Jaki M.
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Read Online
- 1,3-Dipolar cycloaddition reaction of substituted trimethylstannylacetylenes with nitrile oxides
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1,3-Dipolar cycloaddition reaction of trimethylstannylacetylene with nitrile oxides yielded 3-substituted 5-(trimethylstannyl)isoxazoles. On the other hand, the same reaction of (trimethylstannyl)phenylacetylene, -1-hexyne, and -(trimethylsilyl)acetylene
- Sakamoto,Uchiyama,Kondo,Yamanaka
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Read Online
- Generation of an 4-Isoxazolyl Anion Species: Facile Access to Multifunctionalized Isoxazoles
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A direct functionalization of unsubstituted isoxazole (1) was achieved by generation of 4-isoxazolyl anion species (3). An efficient 4-iodination of isoxazole and halogen–metal exchange reaction using a turbo Grignard reagent (iPrMgCl? LiCl) were essentia
- Morita, Taiki,Fuse, Shinichiro,Nakamura, Hiroyuki
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Read Online
- Transition metal catalyzed ring opening reactions of 2-phenyl-3-vinyl substituted 2H-azirines
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Treatment of 2-phenyl-3-vinyl-substituted 2H-azirines with Grubbs' catalyst induces a clean rearrangement and affords products derived from carbon-nitrogen bond cleavage of the 2H-azirine ring. However, when the reaction was carried out using Wilkinson's catalyst in an alcoholic solvent, the only product obtained in high yield corresponded to an α,β-unsaturated oxime.
- Padwa, Albert,Stengel, Thomas
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Read Online
- Unusual Reactivity of 4-Vinyl Isoxazoles in the Copper-Mediated Synthesis of Pyridines, Employing DMSO as a One-Carbon Surrogate
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An efficient protocol for the synthesis of nicotinate derivatives and tetrasubstituted pyridines through a copper-mediated cleavage of isoxazoles has been developed. The highlight of the work is the observation of an unusual reactivity of 4-vinyl isoxazoles under the reaction conditions. DMSO serves as a one-carbon surrogate generating an active methylene group during the reaction to form two C-C bonds. This protocol provides a facile and an expeditious approach for the assembly of densely substituted N-heterocyclic compounds.
- Kumar, Pravin,Kapur, Manmohan
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supporting information
p. 5855 - 5860
(2020/07/30)
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- Catalyst control in positional-selective C-H alkenylation of isoxazoles and a ruthenium-mediated assembly of trisubstituted pyrroles
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High levels of catalyst control are demonstrated in determining the positional selectivity in C-H alkenylation of isoxazoles. A cationic rhodium-mediated, strong-directing group promotes C(sp2)-H activation at the proximal aryl ring whereas, the palladium-mediated electrophilic metallation leads to the C(sp2)-H activation at the distal position of the directing group. Synthetic elaboration of this C-H alkenylation product via ruthenium and copper co-catalysis leads to an efficient method for the assembly of densely substituted pyrroles.
- Kumar, Pravin,Kapur, Manmohan
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supporting information
p. 2134 - 2138
(2019/03/26)
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- Preparation method of isoxazole derivative
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The invention relates to a preparation method of an isoxazole derivative, which comprises the following steps of mixing an propargyl alcohol derivative, a halogen source, an acid and a solvent, and heating to react; adding the hydroxylamine into the react
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Paragraph 0054-0059
(2019/12/02)
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- Method for converting lignin into isoxazole and aromatic nitrile
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The present invention relates to a method for obtaining isoxazole and aromatic nitrile from a lignin model and pre-oxidized birch lignin. The method is characterized in that hydroxylamine hydrochloride and a beta-O-4 model compound containing ketone in the benzyl position, which are used as reaction substrates, undergo oximation condensation Cbeta-O bond fracture under the action of magnesium andother additives to prepare the isoxazole compound, and undergo oximation rearrangement Calpha-Cbeta bond fracture the action of magnesium and other additives to prepare the fragrant nitrile compound.The method can be applied to the conversion of pre-oxidized lignin into the isoxazole and aromatic nitrile. The preparation method comprises the following steps: mixing the beta-O-4 model compound orpre-oxidized birch lignin, hydroxylamine hydrochloride and the additives in an alcohol solvent, adding the obtained mixture into a pressure-resistant container, replacing air in the container with nitrogen, sealing the container, and stirring the mixture at 120 DEG C for 8-12 h to obtain the products isoxazole and aromatic nitrile. The method realizes the obtaining of nitrogen-containing compoundssuch as isoxazole and aromatic nitrile from lignin for the first time, and the reaction process is simple and controllable, and is easy to operate.
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Paragraph 0051; 0052; 0064
(2019/07/04)
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- Cycloisomerization of acetylenic oximes and hydrazones under gold catalysis: Synthesis and cytotoxic evaluation of isoxazoles and pyrazoles
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The synthesis of substituted isoxazoles and pyrazoles through a general cycloisomerization methodology has been reported. The capability of gold(III) chloride to promote cycloisomerization of both α, β-acetylenic oximes and α, β-acetylenic hydrazones is t
- Jeyaveeran,Praveen, Chandrasekar,Arun,M Prince,Perumal
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- Polymer-supported vinyl sulfone as an efficient reagent for the synthesis of 3-monosubstituted isoxazoles
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Polystyrene-supported vinyl sulfone reagent has been developed and used for solid-phase organic synthesis of 3-monosubstituted isoxazoles by 1,3-dipolar cycloaddition reaction with nitrile oxides and subsequent cleavage from the polymer support through an
- Wu, Guo-Jian,Sheng, Shou-Ri,Li, Dan,Xu, Li-Fan,Huang, Zhen-Zhong
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p. 3034 - 3043
(2013/09/12)
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- Regioselective synthesis and slow-release suzuki-miyaura cross-coupling of MIDA boronate-functionalized isoxazoles and triazoles
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The efficient preparation of heterocycles with a range of substitutions ortho to heteroatoms remains as a challenge in organic synthesis, particularly relevant to the construction of druglike molecules due to the ubiquitous presence of such moieties in th
- Grob, Jonathan E.,Nunez, Jill,Dechantsreiter, Michael A.,Hamann, Lawrence G.
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p. 10241 - 10248
(2012/02/05)
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- Efficient and regioselective synthesis of 5-hydroxy-2-isoxazolines: Versatile synthons for isoxazoles, β-lactams, and γ-amino alcohols
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"Chemical Equation Presented" An efficient and highly regioselective protocol was developed for the preparation of 5-hydroxy2-isoxazolines, which have been proved to be versatile synthons for isoxazles, β-hydroxy oximes, and γ-amino alcohols. β-Lactams, commonly embedded in the skeletons of bioactive natural products, were also synthesized in two steps from β-hydroxy oximes, providing a new strategy for the synthesis of this kind of compounds.
- Tang, Shibing,He, Jinmei,Sun, Yongquan,He, Liuer,She, Xuegong
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scheme or table
p. 1961 - 1966
(2010/06/20)
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- A novel synthesis of N-unsubstituted β-enamino thioesters from 3-arylisoxazoles and 3-aryl-5-phenylthio-2-isoxazolines
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A novel procedure for the synthesis of N-unsubstituted β-enamino thioesters, (Z)-S-phenyl 3-amino-3-arylprop-2-enethioates, from 3-arylisoxazoles or 3-aryl-5-phenylthio-2-isoxazolines is described and a plausible mechanism for the reaction is proposed. Some examples of conversion of one β-enamino thioester [(Z)-S-phenyl 3-amino-3-phenylprop-2-enethioate] into N-unsubstituted β-enaminoacyl derivatives (β-enamino esters, β-enamino amides, and β-keto amides) are also reported. Georg Thieme Verlag Stuttgart - New York.
- Vitale, Paola,Di Nunno, Leonardo,Scilimati, Antonio
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experimental part
p. 3195 - 3203
(2010/10/21)
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- Gold(III)-catalyzed synthesis of isoxazoles by cycloisomerization of α,β-acetylenic oximes
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Cycloisomerization of,-acetylenic oximes leading to substituted isoxazoles was achieved using AuCl3 as catalyst, under moderate reaction conditions. The reaction can be applied to various acetylenic oximes and gives good to excellent yields. Th
- Praveen,Kalyanasundaram,Perumal
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experimental part
p. 777 - 781
(2010/06/12)
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- Efficient and regioselective one-pot synthesis of 3-substituted and 3,5-disubstituted isoxazoles
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(Figure Presented) A series of 3-substituted and 3,5-disubstituted isoxazoles have been efficiently synthesized in moderate to excellent yields by the reaction of N-hydroxyl-4-toluenesulfonamide with α,β-unsaturated aldehydes/ketones. This novel strategy is associated with readily available starting materials, mild conditions, high regioselectivity, and wide scope.
- Tang, Shibing,He, Jinmei,Sun, Yongquan,He, Liuer,She, Xuegong
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supporting information; experimental part
p. 3982 - 3985
(2009/12/03)
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- Synthesis of azirines containing aldehyde functionality and their utilization as synthetic tools for five membered oxazoles and isoxazoles
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(Chemical Equation Presented) A simple and useful procedure for the synthesis of azirines containing aldehyde functionality from open chain bromo/chloro-aldehydes at room temperature is reported. The scope of the ring expansion reaction of a number of 3-s
- Brahma, Sulagna,Ray, Jayanta K.
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p. 311 - 317
(2008/09/20)
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- Effect of the aryl group substituent in the dimerization of 3-arylisoxazoles to syn 2,6-diaryl-3,7-diazatricyclo[4.2.0.02,5]octan-4,8-diones induced by LDA
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3-Arylisoxazoles react with LDA in THF at 0 °C affording syn-2,6-diaryl-3,7-diazatricyclo[4.2.0.02,5]octan-4,8-diones (bis-azetidinones), via stereoselective dimerization of an azetinone anion intermediate. A?fragmentation reaction affording arylnitriles may compete with electronic and steric effects of the substituent present in the aryl group being pivotal in determining the outcome of this reaction. An interesting behaviour with LDA of arylnitriles arising from the fragmentation reaction of some 3-arylisoxazoles was also observed. N,N-Diisopropylaminobenzonitriles were in fact formed (plausibly via a benzyne mechanism) from 3-(4-chlorophenyl)isoxazole and 3-(2-chlorophenyl)isoxazole, whereas 3-(2-methylphenyl)isoquinolin-1-amine was isolated starting from 3-(2-methylphenyl)isoxazole and LDA.
- Di Nunno, Leonardo,Vitale, Paola,Scilimati, Antonio
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experimental part
p. 11198 - 11204
(2009/04/11)
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- 2-Isoxazolines with an electron-acceptor substituent at C(5) in reactions with nucleophilic reagents
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Depending on the substituent at position 5 of the heterocycle, reaction of 2-isoxazolines with K-selectride, molybdenum hexacarbonyl, dimsyl sodium, and butyl lithium gave 1,3-cyclo-decomposition, aromatization of the isoxazoline ring, or reduction of the functional groups in the substituted isoxazolines.
- Koroleva,Bondar,Katok,Chekanov,Chernikhova
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p. 362 - 369
(2008/09/21)
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- Stereoselective dimerization of 3-arylisoxazoles to cage-shaped bis-β-lactams syn 2,6-diaryl-3,7-diazatricyclo[4.2.0.02,5]octan-4,8-diones induced by hindered lithium amides
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3-Arylisoxazoles react with hindered lithium amides giving syn 2,6-diaryl-3,7-diazatricyclo[4.2.0.02,5]octan-4,8-diones in good to fair yields. Stereochemistry of the so-obtained cage-shaped bis-β-lactams was assigned by X-ray diffraction analysis. Concerning the mechanism of formation of such hitherto unknown molecules, dimerization of an azetinone anion intermediate stereoselectively induced by Li+ chelation is suggested.
- Di Nunno, Leonardo,Vitale, Paola,Scilimati, Antonio,Simone, Laura,Capitelli, Francesco
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p. 12388 - 12395
(2008/03/13)
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- Traceless solid-phase synthesis of 3-substituted isoxazoles and 3-substituted 5-iodoisoxazolines using polystyrene-supported vinyl selenide
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A novel facile procedure for the traceless solid-phase synthesis of 3-substituted isoxazoles and 3-substituted 5-iodoisoxazolines in good yields and with excellent purities using polymer-supported vinyl selenide is described. The polymeric reagent can be
- Sheng, Shou-Ri,Xin, Qin,Liu, Xiao-Ling,Sun, Wu-Kang,Guo, Rui,Huang, Xian
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p. 2293 - 2296
(2008/02/02)
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- A simple approach to azirines containing an aldehyde functionality and their stabilization as palladium(II) complexes
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A simple and useful method for the synthesis of azirines containing an aldehyde functionality, from open chain bromo/chloro-aldehydes at room temperature and their stabilization as palladium(II) complexes are reported.
- Brahma, Sulagna,Ray, Jayanta K.
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p. 6575 - 6578
(2007/10/03)
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- One-Pot Synthesis of 3-Substituted Isoxazoles from Phenyl Vinylic Selenide
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Phenyl vinylic selenide was adopted for 1,3-dipolar cycloaddition to nitrile oxides and subsequent oxidation-elimination furnished 3-substituted isoxazoles with good yields in a one-pot, two-step transformation.
- Sheng, Shou-Ri,Liu, Xiao-Ling,Xu, Qu,Song, Cai-Sheng
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p. 2763 - 2764
(2007/10/03)
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- Reaction of β-keto ethyleneacetals with hydroxylamine: A correction
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A reaction of 2-(2-nitrobenzoylmethyl)-1,3-dioxolane (3) with hydroxylamine, followed by acid catalyzed cyclization, produced 5-(2- nitrophenyl)isoxazole (5) as the only isolable product, whereas 2- (benzoylmethyl)-1,3-dioxolane (9) under identical condit
- Paradkar,Latham,Krishnaswami
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p. 1497 - 1500
(2007/10/02)
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- Dehydrochlorination of Hydroximic Acid Chlorides by the Use of Organotin Compounds: An Application for Synthesis of Isoxazolines and Isoxazoles
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The reactions of hydroximic acid chlorides and organotin compounds such as bis(tributyltin) oxide or tetraphenyltin, whereby nitrile oxides are generated effectively, are applied to the preparations of isoxazolines and isoxazoles via dipolar cyclo
- Moriya, Osamu,Urata, Yoshikiyo,Endo, Takeshi
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- Application of 3-Oxabicyclohept-6-ene-2,4-dione (Cyclobut-3-ene-1,2-dicarboxylic Anhydride) as an Acetylene Equivalent in Cycloadditions
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The effectiveness and limitations of dioxo-3-oxabicyclohept-6-ene-2,4-dione (cyclobut-3-ene-1,2-dicarboxylic anhydride) as an acetylene equivalent in both 1,3-dipolar and Diels-Alder cycloadditions is reported; it reacted readily with a variety of reagents, including N-benzylideneaniline N-oxide, nitrile oxides, diazomethane, cyclopentadiene, tetracyclone, anthracene, 1,2,5-triphenylphosphole 1-oxide and 1,3-diphenylisobenzofuran.The structures and stereochemistry of the adducts were deduced from their NMR data; in all cases, the sterically favoured anti-isomersare formed exclusively.The configuration of the Diels-Alder adducts are assigned as endo with the exception of that from tetracyclone (and possibly 1,3-diphenylisobenzofuran) for which an exo-structure is assumed on the basis of steric arguments.Adducts were not obtained with several other reagents; possible reasons for this lack of reactivity are discussed.When subjected to flash vacuum pyrolysis, the adducts underwent thermal fragmentation, either by retro-cleavage, or by loss of maleic anhydride to form products that are derived formally from reaction of acetylene in the cycloaddition step.A concerted pathway is proposed for the pyrolytic conversion into the 'formal acetylene cycloadduct' rather than a stepwise radical mechanism.
- Cadogan, J. I. G.,Cameron, Donald K.,Gosney, Ian,Tinley, Edward J.,Wyse, Stuart J.,Amaro, Alicia
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p. 2081 - 2088
(2007/10/02)
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- SYNTHESIS AND STRUCTURE OF 5-HYDRAZINO- AND 5-HYDROXYAMINO-3-ARYL-2-PYRAZOLINES AND -2-ISOXAZOLES
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It was established by the methods of 1H and 13C NMR spectroscopy that the oximohydrazones and bis(hydrazones) of aroylacetic aldehydes exist in the form of the corresponding 5-hydrazino- and 5-hydroxyamino-3-aryl-pyrazolines and -2-isoxazolines.The features of the aromatization of these compounds to the corresponding pyrazoles and isoxazoles were studied.Data on the mass-spectral study of the 5-hydroxyamino-2-pyrazoline-5-hydrazino-2-isoxazoline tautomerism in the gas phase are presented.
- Zelenin, K. N.,Malov, M. Yu.,Ershov, A. Yu.,Terent'ev, P. B.,Kalandarishvili, A. G.,et al.
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p. 772 - 779
(2007/10/02)
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- Synthesis and Chemistry of N-Oxygenated Pyrroles: Crystal and Molecular Structure of a Highly Stable N-Hydroxypyrrole 18-Crown Ether Hydrate
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N-Oxygenated succimides 5-8, 13, and 14, N-oxydithiosuccinimides 10 and 11, and N-oxygenated pyrroles 12, 30a,e, 38, and 39 were synthesized as possible precursors of a pyrrole nitroxide crown ether.N-Methoxypyrrole dithiocrown ethers 21 and 23-27 were pr
- Keana, John F. W.,Heo, Gwi Suk,Mann, Jeffry S.,Nice, Faith L. Van,Lex, Laszlo,et al.
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p. 2268 - 2274
(2007/10/02)
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- CHIRAL ACETYLENES AS SYNTHETIC INTERMEDIATES. V. A REINVESTIGATION ON THE SYNTHESIS OF OPTICALLY ACTIVE ISOXAZOLES
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The synthesis of 3- or 5-alkyl isoxazoles and pyrazoles has been achieved starting from alkyl-substituted acetylenic ketones: the influence of the structure of the carbonyl compound on the isomeric composition of the heterocyclic compound has been studied.Some optically active monoalkyl-substituted isoxazoles have also been prepared: in this context, an investigation on the stereochemistry of the cyclization process has been carried out.
- Falorni, Massimo,Lardicci, Luciano,Giacomelli, Giampaolo
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- SYNTHESIS OF 3-ARYL-4,5-DIHYDRO-5-HYDROXY-1,2-OXAZOLES BY REACTION OF SUBSTITUTED BENZONITRILE OXIDES WITH THE ENOLATE ION OF ACETALDEHYDE.
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By reaction of substituted benzonitrile oxides with the enolate ion of acetaldehyde (quantitatively generated by the known cycloreversion of THF in the presence of n-butyllithium) a number of 3-aryl-4,5-dihydro-5-hydroxy-1,2-oxazoles (previously unknown or, in two cases, only synthesized by different procedures) have been isolated in high yields.Treatment of such hydroxy-isoxalines with some common bases allows their conversion in high yields into the corresponding isoxazoles.
- Di Nunno, L.,Scilimati, A.
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p. 2181 - 2190
(2007/10/02)
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- An Improved Preparation of 5-Unsubstituted Isoxazoles by Borohydride Reduction of 5-Chloroisoxazoles
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The borohydride reduction of 5-chloroisoxazoles offersa useful and unambiguous way to 5-unsubstituted isoxazoles.
- Ponticelli, Fabio,Tedeschi, Piero
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p. 792 - 794
(2007/10/02)
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- THE REACTIONS OF ISOTHIAZOLIUM SALTS WITH NITROGEN NUCLEOPHILIC REAGENTS
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Isothiazolium salts were allowed to react with a number of nitrogen nucleophiles including ammonia, hydrazine, phenylhydrazine, hydroxylamine, and benzylamine.The products obtained suggest that the position of initial nucleophilic attack is at the sulphur
- Hassan, Mohamed E.,Magraby, M. A.,Aziz, Magda A.
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p. 1885 - 1892
(2007/10/02)
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- Metal-carbonyl-Induced Reaction of Isoxazoles. Ring Cleavage and Reduction by Hexacarbonylmolybdenum, Pentacarbonyliron, or Nonacarbonyldi-iron
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In the presence of and water the isoxazoles (1a-f) undergo thermally induced reductive cleavage of the N-O bond to give β-amino enones in good yield.Similar results were obtained by the use of and water with photoirradiation, or of and water with heating.A mechanism involving an N-complexed isoxazolepentacarbonylmolybdenum or isoxazoletetracarbonyliron, and a - or -complexed (β-oxo vinyl)nitrene intermediate is proposed for the reactions.The complexed nitrene moiety could be reduced by the central metal in the presence of water to give amine.Furthermore, treatment of 2-benzoyl- 3-phenyl-2-H-azirine (8a), which is an isomer of 3,5-diphenylisoxazole, with the metal carbonyls and water also resulted in the formation of a β-amino enone possibly via the corresponding complexed (β-oxo vinyl)nitrene.An N-complexed isoxazole-pentacarbonylmolybdenum intermediate was prepared by the photoreaction of with 3,5-dimethylisoxazole.Its characterization, and chemical transformations, have been carried out to investigate the proposed mechanism.
- Nitta, Makoto,Kobayashi, Tomoshige
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p. 1401 - 1406
(2007/10/02)
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- Utilization of Vinylsilanes in Cycloaddition Reactions
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The reaction of several vinylsilanes with benzonitrile oxide, 2-diazopropane, C-carboethoxy-N-phenylnitrile imine, and substituted 1,3-butadienes has been examined.The 1,3-dipolar cycloadditions followed frontier orbital predictions and gave silylated iso
- Padwa, Albert,MacDonald, J. Gavin
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p. 3189 - 3195
(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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- 1,3-DIPOLAR CYCLOADDITION OF BENZONITRILE OXIDE WITH VINYLSILANES
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The reaction of benzonitrile oxide with several vinylsilanes has been found to afford silylated isoxazoles.Relative rates for the cycloaddition reaction were determined.
- Padwa, Albert,MacDonald, J. Gavin
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p. 3219 - 3222
(2007/10/02)
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- SYNTHESIS AND PROPERTIES OF AZOLS AND THEIR DERIVATIVES. PART VI. CYCLOADDITION REACTIONS OF NITROETHYLENE WITH AROMATIC NITRILE N-OXIDES AND SOME CONVERSIONS OF 3-ARYL-5-NITRO-4,5-DIHYDRO-1,2-OXAZOLES
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Reactions of aromatic nitrile N-oxides with nitroethylene lead to formation of 3-aryl-5-nitro-4,5-dihydro-1,2-oxazoles.During heating the above compounds decompose with elimination of nitrous acid, thus affording 3-aryl-1,2-oxazoles.Under nucleophilic reagents a ring opening was observed.
- Baranski, Andrzej,Shvekhgeimer, Genrikh A.
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p. 459 - 467
(2007/10/02)
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- 1-Hydroxypyrazole
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1-Hydroxypyrazole and a process for its preparation by conversion of isoxazolineazoxy compounds at 140°-600° C. The end products obtainable by the process of the invention are valuable starting materials for the preparation of dyes, crop protection agents and drugs.
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- MECHANISM OF FORMATION OF 3,5-DIPHENYLISOXAZOLE IN THE REACTION OF 1,2-DIPHENYLCYCLOPROPANES WITH COPPER NITRATE IN ACETIC ANHYDRIDE
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In reaction with copper nitrate in acetic anhydride the stereoisomeric 1,2-diphenylcyclopropanes give 3,5-diphenylisoxazole.Preliminary isomerization of the cyclopropane hydrocarbons to the corresponding propenes does not occur during the reaction.For the
- Sychkova, L. D.,Kalinkina, O. L.,Shabarov, Yu. S.
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p. 1277 - 1281
(2007/10/02)
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- Reaction of Substituted 4-Phenylpyrimidine 1,3-Dioxides with Phosphorus Oxychloride
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2-Chloropyrimidine 1-oxides are formed in the reaction of substituted 4-phenylpyrimidine 1,3-dioxides with phosphorus oxychloride; in addtition, 2,4-dichloropyrimidines and 3-phenylisoxazoles were isolated.
- Tikhonov, A. Ya.,Sedova, V. F.,Volodarskii, L. B.,Mamaev, V. P.
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p. 383 - 386
(2007/10/02)
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- SITE SELECTIVITY IN THE REACTIONS OF 1,3-DIPOLES WITH NORBORNADIENE DERIVATIVES
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The cycloadditions of arylazides, benzonitrile oxides and diphenylnitrile imine to norbornadiene derivatives 1a-c showed varying degree of site- and stereo-selectivity.With dipolarophile 1a arylazides and benzonitrile oxides attack, preferentially, the electron-poor tetrasubstituted double bond, while in the case of 1b and 1c is the substituted double bond which enters the cycloaddition.By contrast, 2-diazopropane and C-phenyl-N-methylnitrone react with the sole tetrasubstituted double bond of 1a-c in stereo- and site-specific cycloadditions.The quantitative evaluation of the two possible reaction paths was performed by glc analysis.The compounds detected were those arising from Diels-Alder cycloreversions of the thermally labile intermediate adducts 2 and 3 (Scheme 1).The results were rationalized on the basis of a qualitative perturbation treatment which considers frontier orbital interactions only.
- Cristina, D.,Amici, M. De,Micheli, C. De,Gandolfi, R.
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p. 1349 - 1357
(2007/10/02)
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- Halogenation of Vinyl Ketoximes. Synthesis of Isoxazoles and Preparation and Silver Ion-Promoted Reactions of 4-Halo-2-isoxazolines
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Reaction of several α,β-unsaturated ketoximes with N-bromosuccinimide (NBS) gave isoxazoles, but yields were lower and the reaction less general than a similar transformation using iodine under basic conditions.With β,β-disubstituted oximes, 4-halo-5,5-disubstituted-2-isoxazolines were obtained using NBS, iodine, or N-chlorosuccinimide.Treatment of the 4-bromoisoxazolines with silver acetate or silver nitrate caused either elimination with rearrangement to give isoxazoles or substitution at C-4, depending upon the nature of the substituents at C-5.
- Hansen, John F.,Kim, Yong In,McCrotty, Stephen E.,Strong, Scott A.,Zimmer, Douglas E.
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p. 475 - 479
(2007/10/02)
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- Activation of the syn face of an isoxazoline by a carbamate group
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Methyl N-vinylcarbamate adds benzonitrile oxide yielding a mono or a bis-adduct, depending upon the experimental conditions.The configuration of the bisadduct has been elucidated by an X-ray structure determination.
- Albini, Franca Marinone,Vitali, Danila,Oberti, Roberta,Caramella, Pierluigi
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p. 4355 - 4384
(2007/10/02)
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