Heterocyclic polyfluoro-compounds. Part XII. Synthesis and some reactions of 2,3,5,6-tetrafluoro-4-iodopyridine

Abstract

2,3,5,6-Tetrafluoro-4-iodopyridine, prepared by oxidation of 2,3,5,6-tetrafluoro-4-hydrazinopyridine in the presence of methyl iodide or, preferably, by reaction of pentafluoropyridine with sodium iodide in dimethylformamide, is readily converted into 2,3,5,6-tetrafluoropyridylmagnesium iodide or 2,3,5,6-tetrafluoropyridyllithium; some reactions of these organometallic compounds are described. Hydroxide ion, methoxide ion, and ammonia attack 2,3,5,6-tetrafluoro-4-iodopyridine at the 2-position, to give the corresponding 2-substituted trifluoro-4-iodopyridines, but iodide ion appears to attack the 4-iodo-substituent with the formation of the 2,3,5,6-tetrafluoropyridyl anion. Coupling of tetrafluoro-4-iodopyridine by the Ullmann technique affords perfluoro-4,4′-bipyridyl. Reaction of 3-chloro-2,4,5,6-tetrafluoropyridine with sodium iodide in dimethylformamide yields 3-chloro-2,5,6-trifluoro-4-iodopyridine.