Application of the hurd-mori-reaction for the synthesis of tricyclic annelated 1,2,3-thiadiazoles

The synthesis of methyl naphtho1,2-d]1,2,3]thiadiazole-4-carboxylate 1a as well as the corresponding thienobenzo1,2,3]thiadiazoles 1b and 1c is reported using the Hurd-Mori reaction in the key step. Treatment of the readily available tosylhydrazones 10a-c with thionyl chloride surprisingly affords the fully aromatic products 1a-c , instead of the expected annelated 4,5-dihydro1,2,3]thiadiazoles 2a-c . Based on these results a mechanism for the aromatization step with thionyl chloride is proposed.