II. Formation of Thieno-1,2,3-triazines by diazotation of3-amino-thiophene-2 and 4-carboxamide
A series of thieno[3,2-e]-3,4-dihydro-1,2,3-triazin-4-ones (V) and thieno[3,4-e]-3,4-dihydro-1,2,3-triazin-4-ones (VI) were prepared by diazotation of 3-aminothiophene-2-carboxamides (III) and 4-amino-thiophene-3-carboxamides (IV), respectively, both obtained by cyclization of 2-cyanoethylene-1,1-dithiolates with α-halogenocarbonyl compounds. Characteristic differences between the two systems were found in the position of the long-wavelength UV absorption maximum and the acidity of the triazine ring proton. The latter property was reflected in the 1H NMR signal from this proton.
Acta Chemica Scandinavica, 1972, Vol 26, Issue 8, p. 3342-3346