- Improved synthesis of perfluoroalkyl substituted 1,3,4-oxadiazoles as precursors for corresponding 1,2,4-triazoles
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An improved and more efficient synthesis of 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole (2a), 2,5-bis(perfluoroethyl)-1,3,4-oxadiazole (2b), 2-(perfluoroethyl)-5-(trifluoromethyl)-1,3,4-oxadiazole (2d) and 2-(perfluoroheptyl)-5-(trifluoromethyl)-1,3,4-oxadi
- Grünebaum, Mariano,Gerlitz, Anna I.,Buchheit, Annika,Jeschke, Steffen,Daniliuc, Constantin G.,Wiemh?fer, Hans-D.
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- Synthesis of a series of trifluoromethylazoles and determination of pKa of acidic and basic trifluoromethyl heterocycles by 19F NMR spectroscopy
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Trifluoroacetylation at the 5-position of 3,4-dihydro-2H-pyran and the 3-position of 4,5-dihydrofuran, followed by treatment with hydrazine, gave 3-(3-trifluoromethyl-1H-pyrazol-4-yl)propanol and 2-(3-trifluoromethyl-1H-pyrazol-4-yl)ethanol, respectively.In the latter case, an intermediate dimer was isolated.Isomeric 2-(3-trifluoromethyl-1H-pyrazol-5-yl)ethanol was formed by reaction of hydrazine with 6-benzyloxy-1,1,1-trifluorohex-3-yn-2-one and deprotection.Reaction of 3-benzyloxypropylamine with 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole, followed by deprotection, afforded 3-propanol.A series of 2-trifluoromethyl-1H-benzimidazoles and 2-trifluoromethyl-3H-imidazopyridines were prepared by condensation of the appropriate ortho-arenediamine with trifluoroacetic acid.Analysis of the 19F NMR spectra of the trifluoromethylazoles and of 3-trifluoromethylpyridine in aqueous solution at different pHs enabled determination of pKa values.All the compounds evaluated had one or more pKa between 1 and 13, except the triazole.Several compounds were identified as having potential use in measuring pH in biological media by 19F NMR spectroscopy.
- Jones, Brian G.,Branch, Sarah K.,Thompson, Andrew S.,Threadgill, Michael D.
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p. 2685 - 2692
(2007/10/03)
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- Unsaturated nitrogen compounds containing fluorine. Part 10. Reaction of 2,5-dichloro-1,1,1,6,6,6-hexafluoro-3,4-diazahexa-2,4-diene with halide ion and oxygen- and sulphur-centred nucleophiles and of its 2,5-di-iodo analogue with reducing agents and certain nucleophiles
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The azines CF3CR=NN=CRCF3 (R = F, I, PhO, 2,4-Cl2C6H3O, PhS and EtO) are formed by treatment of the title dichloroazine 1 with an excess of the appropriate nucleophile, while reaction with phosphorus (V) sulphide at 180 deg C gives 2,5-bis(trifluoromethyl-1,3,4-thiadiazole in quantitative yield.In the reaction with NaOEt, the compound CF3C(OEt)=NN=C(ONa)CF3 is also produced from the NaOH impurity present.Di-iodoazine 3b undergoes ready reaction with aniline (1:2 molar ratio) and potassium diethyl phenylmalonate (1:1 molar ratio) to afford the monosubstituted compounds PhN=C(CF3)NHN=CICF3 and (EtO2C)2PhC(CF3)=NN=CICF3, respectively.Azine 1 is not reduced by the reagents NaH, LiAlH4 and NaBH4, but di-iodoazine 3b is reduced by tri-n-butyltin hydride at c. 90 deg C to give mainly the compounds CF3CH=NN=CHCF3, CF3CH=NN=CICF3, CFCH2NHN=CICF3 and possibly CF3CH=NNHCH2CF3; with hydrogen iodide at 200 deg C, the major products are the hydroazines CF3CH=NN=CHCF3 and CF3CH=NN=CICF3 and 2,4,6-tris(trifluoromethyl)-1,3,5-triazene.
- Eltoum, Ahmed O. A.,O'Reilly, Neil J.,Tipping, Anthony E.
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p. 101 - 110
(2007/10/02)
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- Perfluoro-1,3,4-oxadiazoles
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Some new polyfluorinated 1,3,4-oxadiazoles have been obtained via a two-step method.The cycloadditions of the 1,3,4-oxadiazoles have been studied and an analysis of the energies of the frontier orbitals calculated by the MNDO method indicates a LUMO-dependent pathway for cycloaddition.
- Vasiliev, N. V.,Lyashenko, Yu. E.,Patalakha, A. E.,Sokolski, G. A.
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p. 227 - 232
(2007/10/02)
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- Reaction of 2,5-Bis(trifluoromethyl)-1,3,4-oxadiazole with Primary Amines. Synthesis of 4-Substituted-3,5-bis(trifluoromethyl)-4H-1,2,4-triazoles
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Reaction of 3,5-bis(trifluoromethyl)-1,3,4-oxadiazole (1a) with primary amines under a variety of conditions conveniently produced 4-substituted-3,5-bis(trifluoromethyl)-4H-1,2,4-triazoles 4a in 26-85percent yield.Alkyl amines reacted with 1a in methanol
- Reitz, David B.,Finkes, Michael J.
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p. 225 - 230
(2007/10/02)
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