Synthesis and Structure of 6,7-Dihydro-2,3-disubstituted 5<i>H</i>-2a-Thia(2<i>a</i>-<i>S</i><sup>IV</sup>)-2,3,4a,7a-tetraazacyclopent[<i>cd</i>]indene-1,4(2<i>H</i>,3<i>H</i>)-dithione
Symmetrical tetraazapentalene derivatives 5 and 6 were synthesized by a convenient one-pot reaction using lithium thioureide/phenacyl chloride/alkyl (or allyl) isothiocyanate system. Unsymmetrical tetraazapentalene derivatives 8 were prepared by the reaction of various isothiocyanates with thiadiazolopyrimidine derivatives 7 which were derived from symmetrical tetraazapentalene derivatives. The structure of 5c was determined by a single crystal X-ray diffraction.