Reaction of tetraazathiapentalene and thiadiazolopyrimidine derivatives with heterocumulenes: Cycloaddition and elimination reactions<i>via</i>hypervalent sulfur intermediates
Tetraazathiapentalene derivative 1 reacts with heterocumulenes such as diphenylketene (2) and 2-pyridylisothiocyanate (5) to give heterocycles 3, 6 and 7 with elimination of methylisothiocyanate. The reactions of thiadiazolopyrimidine derivatives 8a-b with ethoxycarbonyl isothiocyanate (9) and carbon disulfide (11) gives heterocycles 10 and 12 via thermal decomposition of 1:1 cycloadducts C and D which
Tetraazapentalenes (R = CH3 and CH2=CHCH2) reacted with isocyanates to give new types of tetraazapentalenes, (2) and (3). The compounds, 2 and 3 were also obtained by the reaction of isocyanates with thiadiazolopyrimidines.
The synthesis of unsymmetrical tetraazapentalene derivatives was achieved by the reaction of thiadiazole derivatives (2) with various isothiocyanates. Compounds 2 were easily derived from symmetrical tetraazapentalene derivatives.