Polyfluoroheterocyclic compounds. Part XXII. Preparation of and nucleophilic substitution in perfluoro-3,5-dimethylpyridine and perfluoro-3-methylpyridine

Abstract

Perfluoro-3-methylpyridine (II) and perfluoro-3,5-dimethylpyridine (III) are obtained as minor products in the reaction between pentachloropyridine and potassium fluoride at 500°. Compounds (II) and (III) are produced more efficiently by the known reaction of polytetrafluoroethylene with pentafluoropyridine (I) at elevated temperatures. Nucleophilic substitutions in (II) and (III) by ammonia, methoxide, and polyfluoroalkyl anions are described. Substitution occurs at the 2- and 6- as well as the 4-positions in (II) and (III). ¹⁹F N.m.r. spectra of the perfluoroalkyl derivatives indicate fixed conformations of perfluoroisopropyl groups.