The synthesis of [1]benzothieno[2,3‐ c ]quinolines, [1]benzothieno[2,3‐ c ][1,2,4]triazolo[4,3‐ a ]quinoline, and [1]benzothieno[2,3‐ c ]tetrazolo[1,5‐ a ]quinoline

Photocyclization of 3‐chloro‐ N ‐phenylbenzo[ b ]thiophene‐2‐carboxamide 10 afforded [1]benzothieno[2,3‐ c ]‐quinolin‐6(5 H )‐one 11 which was chlorinated to 6‐chloro[1]benzothieno[2,3‐ c ]quinoline 12 followed by dechlorination to give [1]benzothieno[2,3‐ c ]quinoline 5 . A series of 6‐substituted alkoxy and thioalkoxy[1]benzothieno[2,3‐ c ]quinoline derivatives were prepared along with the N ‐methyl quaternary salt 13 of 5 . 6‐Chloro[1]‐benzothieno[2,3‐ c ]quinoline 12 was converted into 6‐hydrazino[1]benzothieno[2,3‐ c ]quinoline 23 which upon treatment with formic acid yielded [1]benzothieno[2,3‐ c ][1,2,4]triazolo[4,3‐ a ]quinoline 6 . Treatment of 23 with nitrous acid resulted in [1]benzothieno[2,3‐ c ]tetrazolo[1,5‐ a ]quinoline 7 . Compounds 6 and 7 are novel heterocyclic ring systems.