The synthesis of monomethoxy[1]benzothieno[2,3‐<i>c</i>]quinolines

Abstract

Abstract A series of monomethoxy[1]benzothieno[2,3‐ c ]quinolines 24‐28 were prepared by photocylization of the appropriate 3‐chloro‐ N ‐phenylbenzo[ b ]thiophene‐2‐carboxamides 9–13 to [1]benzothieno[2,3‐ c ]quinolin‐6( 5H )‐ones 14‐18 followed by chlorination to 6‐chloro[1]benzothieno[2,3‐ c ]quinolines 19‐23 then dechlorination resulting in the title compounds except for 25 which was achieved by direct reduction of 15 . Reaction of 24‐28 with methyl iodide provided the corresponding N ‐methyl quaternary salts 29‐33 . Also, conversion of 4‐meth‐oxy[1]benzothieno[2,3‐ c ]quinolin‐6( 5H )‐one 16 to 4‐methoxy‐6‐methylthio[1]benzothieno[2,3‐ c ]quinoline 35 and 4,6‐dimethoxy[1]benzothieno[2,3‐ c ]quinoline 36 is described.