- Amino- and hydrodefluorination of polyfluoroaromatic amines with aqueous ammonia in a steel autoclave. Synthesis of highly pure tetrafluorophenylenediamines
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The action of aqueous ammonia on liexafhiorobenzene in a steel autoclave at 180-220 °C yields a mixture of isomeric tet rafluorophenylenediamines and 2,4,5-trifhioroplienylene-1,3-diamine. The content of the hydrodefluorination product significantly depends on the reaction temperature and time. Tetrafluorophenylene-1,3-diamine undergoes hydrodefluorination with aqueous ammonia in a steel autoclave at 200 °C to give 2,4,5-trifluorophenylene-1,3- diamine; when the additives of NH4F and/or FeCl3 are present, 2,5-difluorophenylene-1,3-diamine is additionally formed. The hydrodefluorination products are not formed during bis-aminodefluorination of hexafluorobenzene with aqueous ammonia in a glass reactor or with anhydrous ammonia (in a mixture with aprotic solvent) in a steel autoclave.
- Kusov,Rodionov,Vaganova,Shundrina,Malykhin
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experimental part
p. 823 - 827
(2010/08/08)
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- Selective mono-and diamination of polyfluorinated benzenes and pyridines with liquid ammonia
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Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine, octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination. The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed.
- Vaganova,Kusov,Rodionov,Shundrina,Malykhin
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p. 2239 - 2246
(2008/09/20)
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- Catalytic and noncatalytic ammonolysis of chloropentafluorobenzene
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Ammonolysis of chloropentafluorobenzene both in the presence and in the absence of copper(I) salt results mainly in replacement of the para-and ortho-fluorine atoms with respect to chlorine rather than replacement of the chlorine atom. Ammonolysis of 4-chloro-2,3,5,6-tetrafluoroaniline and 2-chloro-3,4,5,6-tetrafluoroaniline in the absence of copper(I) salt yields exclusively the corresponding fluorine substitution products, whereas in the presence of copper(I) salt the chlorine atom is replaced. Successive ammonolysis of chloropentafluorobenzene in the presence of copper catalyst along these two paths was put into the basis of a new method for preparation of 2,3,5,6-tetrafluoro-1,4-phenylenediamine. * This study was financially supported by the Russian Foundation for Basic Research (project no. 99-03-33111), by the Ministry of Science and Technology of the Russian Federation (project no 9.3.01), and by the Ministry of Education of the Russian Federation (project no. 015.05.01.13).
- Selivanova,Pokrovskii,Shteingarts
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p. 404 - 409
(2007/10/03)
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- Facile and Efficient Synthesis of 4-Azidotetrafluoroaniline: A New Photoaffinity Reagent
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p-Azidotetrafluoroaniline (1) was synthesized in 65-73% yield by two different methods employing a stable carbamate intermediate. The first method trapped the intermediate isocyanate generated via a modified Curtius rearrangement with 2-methyl-2-propanol or 2-(trimethylsilyl)ethanol to form the stable carbamates 2d and 2e, respectively. Benzoic acid 2c was first converted to its acid chloride with PCl5. Displacement of the chloride by NaN3 in acetone/water formed the acyl azide. Thermal rearrangement followed by the addition of the appropriate alcohols provided the carbamates. The acid labile carbamate 2d was deprotected with HCl/AcOH to provide 1, while trifluoroacetic acid was required to deprotect 2e and afford 1. In the second path, 1 was synthesized in five steps from pentafluoronitrobenzene (3a) in 65% overall yield. Compound 3a was converted into 4-azidotetrafluoronitrobenzene (3b) with NaN3 in 93% yield and was used without further purification to form 1,4-diaminotetrafluorobenzene (3c) by Sn/HCl reduction in 85% yield. The mono-9-fiuorenylmethoxycarbonyl (FMOC) derivative 3d was formed from 3c with FMOC-Cl and pyridine in EtOAc in 92% yield. Diazotization of 3d under anhydrous conditions with TFA/NaNO2 and NaN3 gave 3e in 87% yield. The aryl azide was formed with concurrent nitration of the 2-position of the fluorenyl system. The protecting group was removed with piperidine to afford 1 in 93% yield. Irradiation of 1 with 254 nm light in cyclohexane gave cyclohexylamine 11, diamine 3c, and azobenzene 12 as the primary products. The formation of C-H insertion product 11 indicates that 1 forms a singlet nitrene upon photolysis. Two heterobifunctional photoaffinity reagents iodoacetamide 9 and dansyl derivative 10 were prepared.
- Chehade, Kareem A. H.,Spielmann, H. Peter
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p. 4949 - 4953
(2007/10/03)
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- Polyhalogenonitrobenzenes and derived compounds: Part 5. Improved preparations of 1,2,3,4-tetrafluoro-5,6-dinitrobenzene and 3,4,5,6-tetrafluoro-1,2-phenylenediamine, and the use of the latter for the synthesis of tetrafluorobenzheterocycles
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The preparation of 2,3,4,5-tetrafluoro-6-nitroaniline (3) by amination of pentafluoronitrobenzene has been speeded up, scaled up and the yield increased by controlling the reaction by TLC monitoring and using 'dry column' chromatography. Compound (3) was readily converted to 1,2,3,4-tetrafluoro-5,6-dinitrobenzene (2) by peroxytrifluoroacetic acid and to 3,4,5,6-tetrafluoro-1,2-phenylenediamine (1) by SnCl2/HCl, Compound (1) was shown to be a versatile intermediate for the synthesis of tetrafluoro-benzimidazoles, -triazoles and -quinoxalines. The fungicidal activity of the latter are reported here.
- Heaton, Alan,Hill, Mark,Drakesmith, Frederick
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p. 133 - 138
(2007/10/03)
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