Heterocyclic analogues of phthalhydrazides: Cyclic hydrazides of pyridine 1-oxide and pyrazine 1,4-dioxide dicarboxylic acids

Abstract

The synthesis of N-oxides of the cyclic hydrazides of pyridine and pyrazine o-dicarboxylic acids is described. Pyrido[2,3-d]pyridazine-5,8-dione 1-oxide, pyrido[3,4-d]pyridazine-1,4-dione 6-oxide, and pyrazino[2,3-d]pyridazine-5,8-dione 1,2-dioxide, were obtained by direct oxidation of the parent hydrazides with peracetic acid. The pyridopyridazine derivatives were also unambiguously synthesized by treating the anhydrides or diesters of the relevant carboxylic acid 1-oxides with hydrazine hydrate.