A process for the production of a fluorobenzonitrile wherein a chlorobenzonitrile having a chlorine atom in an ortho- or para- position with respect to a nitrile group is heated with an alkali metal fluoride at a temperature between 200.degree. and 250.degree. C., in the presence of sulpholane.
A process for producing 2,6-difluorobenzonitrile comprises reducing a chloro fluorobenzonitrile selected from 3-chloro-2,6-difluorobenzonitrile, 3,5-dichloro-2,6-difluorobenzonitrile or a mixture thereof by hydrogen gas in the presence of a palladium or platinum catalyst at a temperature of 0.degree. to 200.degree. C.
A process for the preparation of 3-chloro-4,5-difluorobenzonitrile comprising the steps of (a) reacting an alkali metal fluoride with 4-chloro-3,5-dinitrobenzonitrile to form a 4-fluoro-3,5-dinitrobenzonitrile product; (b) chlorodenitrating the 4-fluoro product of step (a) to form the corresponding 3,5-dichloro-4-fluorobenzonitrile compound; and (c) reacting the 3,5-dichloro-4-fluorobenzonitrile compound prepared in step (b) with an alkali metal fluoride to form 3-chloro-4,5-difluorobenzonitrile.
The present invention describes the novel intermediates 2,3-difluoro-6-nitrobenzonitrile and 2-chloro-5,6-difluorobenzonitrile, a process for their preparation and their advantageous use for the preparation of 2,3,6-trifluorobenzoic acid, which in turn is a valuable intermediate for the preparation of insecticides and antibacterial agents. The intermediates according to the invention are prepared from 2,3,4-trifluoronitrobenzene by fluorine/cyanide exchange and subsequent denitrating chlorination. 2,3,6-Trifluorobenzoic acid can be prepared from the novel intermediates, in a manner known per se in the literature, by simple chlorine/fluorine exchange and subsequent hydrolysis in a process which overall is industrially advantageous and economically favorable.
Organic fluorine compounds such as pentafluorobenzonitrile, tetrafluorophthalonitriles, and pentafluoropyridine are produced by a method which comprises causing a chloro- or bromo-organic compound to react with a fluorinating agent such as an alkali metal fluoride in benzonitrile as a solvent at temperatures in the range of 190.degree. to 400.degree. C. under at least spontaneously generated pressure.
A process for preparing 3,4,6-trifluorophthalonitrile from 3,4,5,6-tetrachlorophthalonitrile comprising the sequential steps of reductively dechlorinating the tetrachlorophthalonitrile, in the presence of a metal in an aqueous acidic medium, to produce 3,4,6-trichlorophthalonitrile and then subjecting the trichlorophthalonitrile to a chlorine-fluorine exchange by reaction with a fluoride source in a polar aprotic solvent.
