Heterocyclic compounds from urea derivatives. Part XIII. Addition–cyclisations of ethoxycarbonylhydrazine and carbodi-imides

Abstract

Ethoxycarbonylhydrazine reacts with two molar proportions of diphenylcarbodi-imide to give the 2 : 1-adduct 1,2-bis-NN′-diphenylamidino-1-ethoxycarbonylhydrazine. This cyclises, with loss of arylamine, to 1-ethoxycarbonyl-4-phenyl-3,5-bisphenylimino-1,2,4-triazolidine, which can be hydrolysed to give 3,5-dianilino-4-phenyl-1,2,4-triazole. The 2 : 1-adduct is hydrolysed by ethanolic hydrochloric acid to 1-carboxy-1,2-bis-NN′-diphenylamidinohydrazine, which can be cyclised by alkali to give 3-anilino-5-hydroxy-4-phenyl-1,2,4-triazole.

Use of di-p-tolyl- or di-p-bromophenylcarbodi-imide results in di-addition and simultaneous loss of ethanol to afford 4-aryl-2-NN′-diarylamidino-5-arylimino-1,2,4-triazolidin-3-ones; these are cleaved to give 4-aryl-3-arylamino-5-hydroxy-1,2,4-triazoles and diarylureas by alkaline hydrolysis. The addition of the carbodi-imide to ethoxycarbonylhydrazine may be performed in two distinct stages with the same results; the intermediate 1-NN′-diarylamidino-2-ethoxycarbonylhydrazine is isolable and a route is thus provided to s-triazolidinones containing two different aryl substituents.