Heterocyclic compounds from urea derivatives. Part XIX. Adducts from diaminoguanidines and aroyl isothiocyanates and their cyclisation

Abstract

1-Aminoamidino-4-aroyl(thiosemicarbazides) are produced in high yield from equimolar proportions of aroyl isothiocyanates and NN′-diaminoguanidine salts in aqueous methanol. They are bases and form hydrazones. Both the adducts and their hydrazones are ring-closed by alkali to 3-aryl-5-mercapto-1,2,4-triazoles. The cyclisation of 1-aminoamidino-4-aroyl(thiosemicarbazides) by acids affords, with loss of ammonia or hydrazine, 2-aroylamino-5-hydrazino-1,3,4-thiadiazoles as main products, and 2-aroylamino-5-amino-1,3,4-thiadiazoles as by-products. Acetic anhydride effects the same cyclisations, but with simultaneous acetylation of the products. The hydrazones of the linear adducts are directly ring-closed by acid to 2-aroylamino-5-alkyl (or aryl) idenehydrazino-1,3,4-thiadiazoles.

The structures of the 2-aroylamino-5-hydrazino-1,3,4-thiadiazoles are confirmed by the identity of the fully benzoylated 2-benzamido-5-hydrazino-1,3,4-thiadiazole, and the tetrabenzoyl derivative of authentic 2-amino-5-hydrazino-1,3,4-thiadiazole.

The interaction of aroyl isothiocyanates and 1,2-diamino-3-arylguanidines in dimethylformamide at 100° yields, with loss of hydrazine, 2-aroylamino-5-arylamino-1,3,4-thiadiazoles in one stage.