Synthesis and S(N)Ar reactions of new dioxins and predioxins

A method for two-step synthesis of dioxin derivatives containing the perfluoropyridine ring has been suggested. It consists of the preparation of corresponding predioxin in the first stage and its cyclization in the next stage. A number of new predioxins have been synthesized using the interaction of polyhalogenpyridines with pyrocatechin and its 4,5-dihaloid derivatives. Formation of dioxins on the basis of not very active arenes occurs smoothly without the necessity for the isolation of predioxin intermediates. For the first time, an interaction of polyhalogenpyridine-containing dioxins and predioxins with nucleophiles of various types (alkyl and arylamines, propylenediamine, hydroxyl anion, and ammonia) has been studied. It was shown that the pyridine fragment does not change the fundamental rules of orientation influence of substituents detemined for non-heterocyclic polyfluorinated arenes. The presence of the labile fluorine atoms reveals a possibility for various modifications of dioxins and predioxins.