Thiophene ring-opening reactions VI. Attempted cyclization towards [fused]-tricyclic system involving a thiolate anion and suitably located electrophilic carbon.

Model -chloro--nitrothieno[2,3-]pyridazines incorporating 1-(aryl) entity appended with -methoxycarbonyl or trifluoromethyl group were prepared intramolecular cyclization of their respective -arylhydrazone precursors. Interaction of these substrates with '-(-fluorophenyl)benzothiohydrazide, in the presence of NEt, furnished the respective 1,3,4-thiadiazoline-pyridazine thiolate hybrids that were -methylated to produce the corresponding "sulfanyl" derivatives. Their structures were deduced from spectral data, and confirmed by single-crystal X-ray diffraction.