The synthesis of substituted [1]benzothieno[2,3‐ c ]quinolines and their N ‐methyl quaternary salts

Four substituted [1]benzothieno[2,3‐ c ]quinolines 14a‐14d were prepared by photocyclization of the appropriate carboxamides 8a‐8d to the corresponding [1]benzothieno[2,3‐ c ]quinolin‐6(5 H )‐ones 12a‐12d followed by chlorination to 6‐chloro[1]benzothieno[2,3‐ c ]quinolines 13a‐13d and dechlorination resulting in the title compounds. Treatment of 14a‐14d with iodomethane furnished the corresponding N ‐methyl quaternary salts 5a‐5d .