Heterocyclic compounds from urea derivatives. Part XVII. Reactions of 1-phenylcarbonohydrazide and 1-phenylthiocarbonohydrazide with carbodi-imides

Abstract

Equimolar quantities of 1-phenylcarbonohydrazide and diarylcarbodi-imides react additively in dimethylformamide, giving good yields of 1-NN′-diarylamidino-5-phenylcarbonohydrazides. These are readily cyclised by aqueous alkali to 4-anilino-3-arylamino-1,2,4-triazolin-5-ones, with loss of arylamine. Thermolysis effects the same cyclisation, but produces additionally (and sometimes exclusively) 4-aryl-3-arylamino-1,2,4-triazolin-5-ones, with elimination of phenylhydrazine.

1-NN′-Diarylamidino-5-phenylthiocarbonohydrazides are obtained analogously from 1-phenylthiocarbonohydrazide, and are converted by aqueous alkali into 4-anilino-3-arylamino-1,2,4-triazoline-5-thiones. Corresponding members of the thioxo- and oxo-1,2,4-triazoline series are convertible into each other. In contrast, ethanolic alkali simultaneously dehydrogenates and cyclises 1-NN′-diarylamidino-5-phenylthiocarbonohydrazides to 2-arylamino-5-phenylazo-1,3,4-thiadiazoles, the structure of which is confirmed by their synthesis from 2-amino-5-anilino-1,3,4-thiadiazole and nitrosobenzene. 2-Anilino-5-phenylazo-1,3,4-thiadiazole yields a monoacetyl and two isomeric monobenzyl-derivatives.