- Diazo Activation with Diazonium Salts: Synthesis of Indazole and 1,2,4-Triazole
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A donor/acceptor diazo activation strategy, processing via condensation using diazonium salts without the addition of any other catalysts or reagents, is reported. The diazenium intermediate was found to undergo cyclization to give indazoles in excellent yields. Alternatively, in the presence of nitriles, substituted 1,2,4-triazoles were obtained in good to excellent yields. This interesting diazenium route provides a new approach to achieve complex heterocycle synthesis under mild conditions.
- Li, Xuming,Ye, Xiaohan,Wei, Chiyu,Shan, Chuan,Wojtas, Lukasz,Wang, Qilin,Shi, Xiaodong
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p. 4151 - 4155
(2020/06/05)
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- Novel process for synthesis of 1,2,4-triazoles: Ytterbium triflate-catalyzed cyclization of hydrazonyl chlorides with nitriles
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A series of 1,3,5-trisubstituted 1,2,4-triazoles were synthesized via the intermolecular cyclization of hydrazonyl chlorides with nitriles catalyzed by ytterbium triflate [Yb(OTf)3]. The amount of catalysis was discussed and Yb(OTf)3 could be reused without loss of activity. Copyright Taylor & Francis, Inc.
- Su, Weike,Yang, Dianwen,Li, Jianjun
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p. 1435 - 1440
(2007/10/03)
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- Reactions of Nitrile Oxides and Nitrile Imines with Derivatives of 4,5-Dihydrooxazole and 4,5-Dihydrothiazole and with Related Compounds
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2-Phenyl-4,5-dihydrooxazole 4 gives a cycloadduct 6 when treated with benzonitrile N-oxide; with a 1-oxoalkene- or α-oxoarene-nitrile N-oxide (RCOCNO), an open chain product, RCO2CH2N(CN)COPh , is obtained.The six-membered-ring analogue of compound 4 undergoes similar reactions.Depending on the nature of the ring substituents, a substituted 4,5-dihydrooxazole reacts with a C,N-diarylnitrile imine, to give either a cycloadduct, e.g. 17, or a 1,2,4-triazol-4-ium salt, e.g. 19.The product from the reaction of 4,5-dihydro-2-methylthiazole 1b with a nitrile imine depends upon the nature of the C- and N-substituents in the latter.In all cases it is postulated that a 4-substituted triazolium salt 24 is formed.This may lose thiirane to give a substituted 1,2,4-triazole 25, or it may react with a second molecule of the precursor of the nitrile imine, to give a 4-substituted 1,2,4-triazolium salt, e.g. 27, in which the precursor moiety is incorporated into the C-4 side chain.
- Kennewell, Peter D.,Miller, David J.,Scrowston, Richard M.,Westwood, Robert
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p. 3563 - 3566
(2007/10/02)
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- An approach to 1-aryl-1,2,4-triazoles
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A series of different 1,3,5-trisubstituted 1,2,4-triazoles 9 have been readily prepared by simple oxidation of corresponding N-alkylamide arylhydrazones (amidrazones) 5 with hydrogen peroxide or potassium permanganate.
- Buzykin,Bredikhina
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- Formation of 1,2,4-Triazoles by Cation Radical Induced Oxidative Addition of Arylhydrazones of Benzaldehyde and Butyraldehyde to Nitriles
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1,3,5-Trisubstituted 1,2,4-triazoles have been made in excellent yields by oxidative cycloaddition of arylhydrazones of benzaldehyde and butyraldehyde to aceto-, propio-, and acrylonitrile.Oxidation was achieved with the cation radicals thianthrenyl perchlorate (Th(radical)+ClO4-) and tris(2,4-dibromophenyl)aminium hexachloroantimonate (Ar3N(radical)+SbCl6-).The triazoles thus had a phenyl, p-nitrophenyl, or 2,4-dinitrophenyl group in the 1-position, either a phenyl or propyl group in the 3-position, and a methyl, ethyl, or vinyl group in the 5-position.The formation of 5-vinyltriazoles was confirmed by their hydrogenation to 5-ethyltriazoles, which were obtained also by cycloadditions to propionitrile.New triazoles (eight) were also synthesized by a known alternative route, but in lower yields.The fact that 5-vinyltriazoles were formed instead of 5-cyano-2-pyrazolines shows that cation radical induced cycloadditions do not go through the nitrilimines.Cycloadditions with N-phenylbenzohydrazonoyl chloride and acrylonitrile in the presence of aluminum chloride and of triethylamine were carried out for comparison with the corresponding cation radical reaction.
- Shine, Henry J.,Hoque, A. K. M. Mansurul
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p. 4349 - 4353
(2007/10/02)
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- REACTION OF BENZONITRILE N-(p-NITROPHENYL)IMIDE WITH 5-SUBSTITUTED TETRAZOLES: A NEW ROUTE TO SUBSTITUTED 1,2,4-TRIAZOLES VIA N-HYDRAZONOYLTETRAZOLES
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A wide range of phenyl 5-R-substituted (R = aryl, alkyl, amino, halo, H) 1- and 2-hydrazonoyltetrazoles has been synthesized.Substituent effects on the orientation of nitrile imide attack on 5-aryltetrazoles are reported.Thermolysis and fragmentation of t
- Butler, Richard N.,Fitzgerald, Kevin J.
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p. 1587 - 1592
(2007/10/02)
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