Preparation of [1,2,4]triazoloquinazolinium betaines and molecular rearrangements of putative [1,2,4]triazolo[4,3-a][1,3,5]triazinium betaines

Abstract

3H-10λ⁵-[1,2,4]Triazolo[4,3-a]quinazolin-10-ylium-1-aminides were prepared by treating 1-methyl-1-(4-methylquinazolin-2-yl)-4-(aryl)thiosemicarbazides with dicyclohexylcarbodiimide (DCC); the crystal and molecular structure of one such derivative has been investigated by X-ray crystallography. A quinazolinium-1-olate and a -thiolate analogue of the aminides have also been prepared. 2-(1-Methylhydrazino)-4,6-dimethyl-1,3,5-triazine was synthesised by condensing the free base derived from 1-methyl-1-aminoguanidine sulfate with ethyl N-acetylacetamidate. A series of thiosemicarbazides was prepared by treating the above hydrazine derivative with isothiocyanates. One such thiosemicarbazide was treated with DCC to afford a 1,2,4,6-tetraazahexadiene derivative. Thermal reaction of 1-(4,6-dimethyl-1,3,5-triazin-2-yl)-1,3-dimethyl-4-(phenyl)isothiosemicarbazide gave a product of dimerisation, the structure of which was elucidated by X-ray crystallography.