| 摘要 |
Pentachloropyridine or tetrafluoropyridine are heated with anhydrous KF in the absence of a solvent to give fluorinated pyridines. Pentachloropyridine gives pentachloropyridine, 3-chlorotetrafluoropyridine and 3,5-dichlorotrifluoropyridine. Mixed tetrachloropyridines give 3 - chloro - 2,4,6 - trifluoropyridine, two isomeric dichlorodifluoropyridines, one of which is 3,5 - dichloro - 2,6 - difluoropyridine, and two isomeric trichloromonofluoropyridines. The starting materials are obtained by reacting pyridine with PCl5 to give di-, tri-, tetra- and penta-chloropyridines. The fluoropyridines produced by the above process may be subsequently reacted with ammonia, hydrazine or an alkali metal alkoxide to give a product containing, respectively, an amino, hydrazino or alkoxy group at position 2 and/or at position 4. The compounds produced according to the above processes may undergo further reactions to give other substituted polyfluoropyridines. Thus:- (a) Pentafluoropyridine reacts at position 4 with pentafluorophenyl magnesium bromide to give 4 - (pentafluorophenyl) - tetrafluoropyridine. (b) An amino group may be converted to bromo by the Sandmeyer reaction. (c) 4 - Bromo - tetrafluoropyridine may be treated with copper to give octafluoro-4,41-bipyridyl. (d) Compounds containing no fluorine at position 4 react at positions 2 and/or 6 with ammonia, alkali metal hydroxides and alkali metal alcoholates to give the corresponding amino, hydroxy or alkoxy compounds. (e) A hydrazino group at position 4 may be converted to an amino group by reaction with aqueous hydriodic acid, or to a hydrazone by reaction with a carbonyl compound. (f) An amino group at position 2 or 4 may be converted to -NO2 by reaction with H2O2 and trifluoroacetic anhydride. (g) 4 - Bromo - compounds may be converted to the corresponding magnesium bromides which then undergo the normal reactions of Grignard reagents. (h) Bromine may be replaced by hydrogen by treatment with copper (cf. reaction (c) above). (i) Methoxy groups may be converted to hydroxy by treatment with aqueous hydriodic acid. (j) Reaction of 4-hydrazino-tetrafluoropyridine with calcium hypochlorite and benzene gives 4 - phenyl - tetrafluoropyridine. (k) Reaction of pentafluoropyridine with phenyl-lithium gives 4-phenyl-tetrafluoropyridine. (l) 3,5 - Dichloro - trifluoropyridine is reacted with magnesium and ethylene dibromide, and the Grignard product is hydrolysed to 3-chloro-2,4,6-trifluoropyridine. Reference has been directed by the Comptroller to Specification 1,059,231. |
