Synthesis of 8‐substituted naphtho[2,1‐ b ]thiophenes with cationic side chains at position 4

A series of five 8‐substituted α‐[bis(2‐hydroxyethyi)aminoethyl]naphtho[2,1‐ b ]thiophenes 7 and a series of seven N ‐(3‐dimethylaminopropyl)‐8‐substituted naphtho[2,1‐ b ]thiophene‐4‐carboxamides 8 have been synthesized. The naphtho[2,1‐ b ]thiophene‐4‐carboxylic acids 4 were prepared by photooxidative cyclization of α‐(2‐thienyi)‐β‐arylacrylic acids 3. The carboxylic acids 4 were converted by a conventional five step route involving α‐bromoketone intermediates to the a‐[bis(2‐hydroxyethyl)aminomethyl]‐8‐substituted naphtho‐[2,1‐6]thiophene‐4‐methanols 7 and by a standard two‐step amide preparation to the N ‐(3‐dimethylaminopropyl)‐8‐substituted naphtho[2,1‐6]thiophene‐4‐carboxamides 8 .