A study of the condensation between o-phenylenediamine and pulvinic acid derivatives

The product (IXb) of the condensation at about 200° of o-phenylenediamine with pulvinic acid, vulpinic acid and pulvinic dilactone yields by hydrolytic fission 2-benzylbenziminazole and by ozonolysis 2-benzoylbenziminazole. Vulpinic acid methyl ether also gives IXb as the main product and its N-methyl derivative as minor product, showing that under the basic conditions and high temperature used, demethylation of the enol ether and partial transfer of methyl group to nitrogen occur. Methylation of IXb yields the N-methyl compound; this and its spectral properties show that it is in the keto form. At room temperature, vulpinic and pulvinic acids do not react; however, pulvinic dilactone yields two products: (1) an intermediate amide forming IXb on heating and (2) a product resulting from the condensation of one molecule of diamine with two of the dilactone