- Polyhalogenoheterocyclic Compounds. Part 23. Mechanism of Thermal Rearrangements of Perfluoropyridazine and Perfluoroalkylpyridazines
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Rearrangement of perfluoro-4,5-di-s-butylpyridazine (4) to a mixture of perfluoro-4,5-di-s-butylpyrimidine (13) and -2,5-di-s-butylpyrazine (20), occurs at 300 deg C, in a sealed tube.Cross-over experiments between various fluorinated pyridazine derivatives and, also, doubly 15N-labelled derivatives, rule out any rearrangement mechanism involving a cycloaddition process.Compound (4) and other fluorinated compounds act as promoters for the rearrangement of various fluorinated pyridazine derivatives and this process is now most reasonably regarded as a free-radical promoted formation of valence isomers.
- Chambers, Richard D.,Musgrave, W. Kenneth R.,Sargent, Colin R.
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- Reactions Involving Fluoride Ion. Part 40. Amines as Initiators of Fluoride Ion Catalysed Reactions
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Tetrakis(dimethylamino)ethene (TDAE) and trimethylamine react with anhydrous unsaturated fluorocarbons to produce, 'in situ', powerful fluoride-ion sources.These are used to iniate carbon-carbon bond forming reactions eg. oligomerisation and polyfluoroalkylation, and many of these reactions occur efficiently in the absence of a solvent.
- Chambers, Richard D.,Gray, William K.,Korn, Stewart R.
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p. 13167 - 13176
(2007/10/03)
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- Process for the preparation of 5-fluoropyrimidines
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5-Fluoropyrimidines are obtained in an advantageous manner from halogenated 5-unsubstituted pyrimidines, when these are reacted with elemental fluorine in the presence of a solvent.
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- SUBSTITUTIVE AROMATIC FLUORINATION WITH CHLORINE PENTAFLUORIDE
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In contrast to limited substitutive fluorination of aromatics with halogen fluorides such as ClF, ClF3, BrF3 and IF5, fluorination is the predominant reaction path with ClF5.Under non-catalytic liquid phase conditions, benzene was converted to fluorobenzene (54percent yield) and chlorobenzene (37percent yield), respectively.For a heterocyclic substrate, i.e. 2,4,6-trifluoropyrimidine, sunstitutive fluorination predominated over chlorination.Three possible fluorination mechanisms are discussed.A transition complex of ClF5 with benzene is favored.Enhanced exchange fluorination of CCl4 was effected with ClF5 (CF2Cl2 >> CFCl3 > CF3Cl) as compared with ClF3 (CFCl3 >> CF2Cl2)
- Boudakian, Max M.,Hyde, Gene A.
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p. 435 - 446
(2007/10/02)
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- Detection of a Transient after Flash Photolysis of Perfluorinated Diazines in the Gas Phase
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Mass spectrometric evidence indicates that flash photolysis of tetrafluoro-pyridazine, -pyrimidine, and -pyrazine produced short-lived isomers with a fulvene-type structure; the values of the rate constants for the formation and decay are given.
- Ratajczak, Emil,Price, Dennis
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p. 315 - 317
(2007/10/02)
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- LES FLUORATIONS COMPAREES DES CHLOROPYRIMIDINES ET DE LA CHLORO-S-TRIAZINE
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The fluorinations of tetrachloropyrimidine, 2,4,6-trichloropyrimidine and trichloro-s-triazine were carried out in sealed tubes with KF in presence of inert gas and then compared.The fluorinated derivatives C4FxClyN2 with x + y = 4, O - were investigated and compared; the molar yields were found to be always higher than 50percent in our experimental conditions.We compare with the fluorinations of 2,4 and 4,6-dichloropyrimidine.It is possible to obtain directlyin good proportions, such fluorinated derivatives as 5-chlorotrifluoropyrimidine, trifluoropyrimidine and others.At high temperature (4OO deg C for 16h), tetrachloropyrimidine, in presence of KF, gave products of pyrolysis and condensation such as the fluorinated derivatives of C6Cl6 and C5Cl5N: C6FCl5, C6F2Cl4... or C5FCl4N, C5F2Cl3N...
- Hitzke,J.
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p. 385 - 402
(2007/10/02)
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