NDLI: Polyfluoroheterocyclic compounds. Part XVII. Preparation and nucleophilic substitution of tetrafluoropyrazine and the orientational effect of substituents in polysubstitution

Content Provider	Royal Society of Chemistry (RSC)
Author	Musgrave, W. K. R. Chambers, R. D. Allison, C. G. MacBride, J. A. H.
Copyright Year	1970
Abstract	Chlorination of various pyrazine derivatives, preferably pyrazine-2,3-dicarboxylic acid, provides tetrachloropyrazine, which gives tetrafluoropyrazine when heated with potassium fluoride. A series of trifluoropyrazines has been obtained by reaction between tetrafluoropyrazine and nucleophiles in which the attacking atom is carbon, nitrogen, or oxygen. Trifluorohydroxypyrazine does not tautomerise appreciably to a pyrazinone. The structures of the difluoropyrazines resulting from a second nucleophilic substitution have been deduced by 19F n.m.r. spectroscopy, and substituent shielding parameters obtained from trifluoropyrazines give notably consistent values when applied to difluoropyrazines. Alkyl and chlorine substituents in a trifluoropyrazine direct nucleophilic attack to the para-, and alkoxy-substituents to the ortho-position. Tetrafluoropyrazine is also substituted in the presence of protic or Lewis acids; tetrabromopyrazine and a dibromodifluoropyrazine are obtained by use of aluminium bromide and hydrogen bromide. Various other halogeno-fluoropyrazines are obtained by incomplete fluorination of tetrachloropyrazine or from reaction of trifluorohydrazinopyrazine with metal halides.
Starting Page	1023
Ending Page	1029
Page Count	7
File Format	PDF
ISSN	00224952
Volume Number	0
Issue Number	8
Journal	Journal of the Chemical Society C: Organic
DOI	10.1039/J39700001023
Language	English
Publisher	Royal Society of Chemistry
Access Restriction	Open
Subject Keyword	Aluminium bromide Spectroscopy Chlorine Tautomer Substituent Nitrogen Carbon Fluorine-19 nuclear magnetic resonance Lewis Pyrazine Nucleophilic substitution Potassium fluoride Nucleophile Hydrogen bromide
Content Type	Text
Resource Type	Article
Subject	Organic Chemistry

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