共查询到20条相似文献,搜索用时 15 毫秒
1.
Antonio Palumbo Piccionello Andrea Pace Paola Pierro Ivana Pibiri Silvestre Buscemi Nicolò Vivona 《Tetrahedron》2009,65(1):119-4751
The reaction of 5-polyfluoroaryl-1,2,4-oxadiazoles with methylhydrazine has been studied and the synthesis of fluorinated N-methylindazoles has been realized. Rearrangement reactions showed predominantly formation of N(1)-methylindazole regioisomers. Starting compounds were preliminarily functionalized at the polyfluoroaryl moiety through fluorine displacement with nucleophiles (methanol, methylamine, dimethylamine), allowing the obtainment of target indazoles substituted at the C(6) position. 相似文献
2.
Buscemi S Pace A Palumbo Piccionello A Macaluso G Vivona N Spinelli D Giorgi G 《The Journal of organic chemistry》2005,70(8):3288-3291
The reaction of 3-benzoyl-5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine has been investigated, evidencing the possibility of competitive reaction paths. Nucleophilic addition of the hydrazine to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure with enlargement, leads with high yield and in very mild experimental conditions to the formation of Z-oximes of 3-perfluoroalkyl-6-phenyl-2H-1,2,4-triazin-5-ones (11a-c) as major products of the reaction. In turn, the hydrazine can attack the electrophilic carbonyl carbon giving 4-perfluoroacylamino-5-phenyl-2H-1,2,3-triazoles (13a-c) through the well-known Boulton-Katritzky rearrangement of the intermediate hydrazones. 相似文献
3.
The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles has been investigated. Nucleophilic addition of the reagent to the C(5)-N(4) double bond of the oxadiazole ring, followed by ring-opening and then ring-closure involving the beta-nitrogen atom of the hydrazino moiety and the C(3) of the oxadiazole ring, explains the formation of 5-perfluoroalkyl-1,2,4-triazoles as final products. Useful applications in synthesis of this uncommon hydrazinolysis can be claimed. 相似文献
4.
Pace A Buscemi S Vivona N Silvestri A Barone G 《The Journal of organic chemistry》2006,71(7):2740-2749
The photoinduced competitive rearrangements of 5-perfluoroalkyl-3-amino(N-alkylamino)-1,2,4-oxadiazoles have been investigated by DFT calculations and UV-vis spectroscopy. The observed product selectivity depends on the number of hydrogen atoms present in the amino moiety and involves two or three possible routes: (i) ring contraction-ring expansion (RCRE), (ii) internal-cyclization isomerization (ICI), or (iii) C3-N2 migration-nucleophilic attack-cyclization (MNAC). UV absorption and fluorescence spectra of the reactants, and vertical excitation energy values, calculated by time dependent DFT, support the involvement of a neutral singlet excited state in the photoexcitation process. The values of the standard free energy of the most stable prototropic tautomers of reactant, products, proposed reaction intermediates, and deprotonated anionic transition states allowed us to rationalize the competition among the three rearrangements, in agreement with chemical trapping experiments, in terms of: (i) the evolution of the excited state toward three stable ground-state intermediates, (ii) tautomeric and deprotonation equilibria occurring in methanol solution for each intermediate, and (iii) relative stabilization of intermediates and transition states in the thermally driven section of the reaction. 相似文献
5.
A series of 6-substituted fluorinated indazoles has been obtained through an ANRORC-like rearrangement (Addition of Nucleophile, Ring-Opening and Ring-Closure) of 5-tetrafluorophenyl-1,2,4-oxadiazoles with hydrazine. The initial addition of the bidentate nucleophile to the electrophilic C(5) of the 1,2,4-oxadiazole ring, followed by ring opening and ring closure, leads to the formation of fluorinated indazoles in high yield under mild experimental conditions. Functionalization of the C(6) in the final indazole nucleus was preliminarily achieved through a nucleophilic aromatic substitution on the starting 5-pentafluorophenyl-1,2,4-oxadiazole. 相似文献
6.
Papers on the synthesis of dialkylhydrazones of , -unsaturated aldehydes have appeared comparatively recently ¦1, 2¦. Hitherto the chemical properties of these compounds have not been studied very much. 相似文献
7.
Reactions of substituted 5-dinitromethyl-3-phenyl-1'2'4-oxadiazoles with arylethenes of variousnucleophilicity, number, position of substituents attached to the double bond give rise to nitroalkenes andsecondary products resulting from -nitroketones or nitroalcohols O-alkylation. The direction of transforma-tions in the arising ion pair is governed predominantly by steric effects. 相似文献
8.
A series of 3,5-disubstituted-1,2,4-oxadiazoles ( 2 ) were prepared from a mono- or dichlorophenyl-substituted amidoxime and (i) an acid chloride, (ii) an isatoic anhydride, or (iii) a β-keto ester. Although cyclizations of the same amidoximes with acetaldehyde gave 4,5-dihydro-5-methyl-substituted derivatives ( 5 ), that annulation procedure either failed or gave low yields with other aldehydes. A novel alternative method, the diborane reduction of 2 , has been found to be a generally applicable procedure for preparing 5 . The reduction is regioselective, i.e., only the 4,5-(C=N) linkage is reduced even when a large excess of diborane is present. 相似文献
9.
V. N. Yarovenko V. Z. Shirinyan I. V. Zavarzin M. M. Krayushkin 《Russian Chemical Bulletin》1991,40(9):1924-1924
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2166–2167, September, 1991. 相似文献
10.
Yang-I Lin Joseph J. Hlavka Panayota Bitha S. A. Lang 《Journal of heterocyclic chemistry》1983,20(6):1693-1695
Monothiodiacylamines reacted regiosepecifically with hydrazines and hydroxylamine to give substituted 1,2,4-triazoles and 1,2,4-oxadiazoles in excellent yields. 相似文献
11.
Nucleophilic substitution of chlorine with hydrazine and methylhydrazine in chlorinated pyridazines and pyridazones 总被引:2,自引:0,他引:2
A. B. Baranov V. G. Tsypin A. S. Malin B. M. Laskin 《Russian Journal of Applied Chemistry》2004,77(12):1997-2000
The reactions of methylhydrazine and hydrazine hydrate with chlorinated pyridazines and pyridazones were studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 2021–2024.Original Russian Text Copyright © 2004 by Baranov, Tsypin, Malin, Laskin. 相似文献
12.
Russian Journal of Organic Chemistry - 相似文献
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14.
A reaction of 3-chloro-1,2,4-oxadiazoles with allylamine and diallylamine has been investigated. 3,3a,4,5-Tetrahydroisoxazolo[3,4-d]pyrimidines are produced through a tandem ANRORC/[3 + 2]cycloaddition pathway consisting of the addition of allylamine to the 1,2,4-oxadiazole, followed by ring opening, nitrone formation, and finally cycloaddition. 3-N-Allylamino-1,2,4-oxadiazoles were also obtained as minor products through a classical SNAr. Conversely, a reaction with diallylamine produces 3-N,N-diallylamino-1,2,4-oxadiazole and imidazoline through tandem SNAr/aziridination and nucleophilic ring opening. 相似文献
15.
It is shown that the first step in the reduction of the investigated oxadiazoles on a dropping mercury cathode in dimethylformamide corresponds to two-electron cleavage of the N-O bond. The degree of reduction is determined by the nature and position of the substituents in the oxadiazole ring and by the rate of protonation of the intermediately formed particles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 38–40, January, 1979. 相似文献
16.
Tarasenko M. V. Kofanov E. R. Baikov S. V. Krasovskaya G. G. Danilova A. S. 《Russian Journal of Organic Chemistry》2017,53(7):1085-1089
Russian Journal of Organic Chemistry - A procedure has been developed for the synthesis of (5-alkenyl-1,2,4-oxadiazol-3-yl)anilines by selective reduction of the nitro group in... 相似文献
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18.
V. N. Yarovenko V. Z. Shirinyan I. V. Zavarzin M. M. Krayushkin 《Russian Chemical Bulletin》1994,43(1):114-117
The reaction of amidoximes with cyanoguanidine in the presence of Lewis acids affords 3-substituted 5-guanidino-1,2,4-oxadiazoles. A study of the reaction of15N-labeled chloroacetamidoxime with cyanoguanidine showed that the formation of the oxadiazole ring occursvia the elimination of the amino group from the amidoxime fragment. 1,2,4-Oxadiazoles bearing the imidazole or pyrimidine moiety were synthesized.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 118–121, January, 1994. 相似文献
19.
D. S. Kosyakov A. S. Amosov N. V. Ul’yanovskii A. V. Ladesov Yu. G. Khabarov O. A. Shpigun 《Journal of Analytical Chemistry》2017,72(2):171-177
5-Nitro-2-furaldehyde, a new derivatizing agent for the spectrophotometric determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine is proposed. It is characterized by high solubility in water and by a substantial difference in the positions of absorption bands of the formed colored derivatives. The kinetics of the reaction of analyte derivatization is studied, and reaction conditions (pH 5, concentration of derivatizing agent 2 mM, 60° C, duration 40 min) are optimized. The limits of detection are 5, 3, and 1.5 μg/L for hydrazine, methylhydrazine, and 1,1-dimetlhydrazine, respectively. A possibility of the spectrophotometric determination of analytes in their simultaneous presence using the Firordt method is shown. The developed approach is successfully applied to the analysis of polluted peat bog soil selected at a place of impact of the first step of a carrier rocket. 相似文献
20.
The synthesis of 3,5-substituted 1,2,4-oxadiazoles on solid support is described. Benzoic acids bound to the Wang linker on a polystyrene resin are activated and allowed to react with N-hydroxyamidines. The resulting acylated N-hydroxyamidines are converted into 1,2,4-oxadiazoles at 125°C. 相似文献