Cyclotetramerisations of sulfanyl substituted pyrazine-2,3-dicarbonitriles and phthalonitriles

Pyrazine-2,3-dicarbonitriles, substituted with strong to moderate electron withdrawing sulfanyl groups, have been synthesised. One of these pyrazines, substituted with two 5-methyl-1,3,4-thiadiazole-2-sulfanyl groups, has shown significant anticancer reactivity. Two phthalonitriles, substituted with thiadiazole-sulfanyl groups have been synthesised.The reagents Zn(OAc)2 and Zn(quinoline)2Cl2, dissolved in quinoline, were reacted with the above monomers to obtain zinc azaphthalocyanines and phthalocyanines. Only zinc azaphthalocyanines with moderate electron withdrawing sulfanyl groups were obtained, whereas one phthalonitrile, substituted with two 5-methyl-1,3,4-thiadiazole-2-sulfanyl groups, gave the corresponding zinc phthalocyanine. Some pyrazine-2,3-dicarbonitriles, substituted with one 2-thienyl and one sulfanyl group, gave mixtures of the corresponding zinc azaphthalocyanine constitutional isomers. New compounds were characterised by elemental analysis, UV–vis, IR, 1H and 13C NMR spectroscopies.