The synthesis of four isomeric bisthienothiepinones

The displacement reaction between sodium thiophene-3-thiolate and methyl 3-(bromomethyl)thiophene-2-carboxylate ( 5 ) gave the expected thioether 7a . Basic hydrolysis afforded the carboxylic acid 7b ; conversion to the acid chloride, and treatment of the latter with stannic chloride then produced the bisthienothiepinone 1 . Using analogous reactions the isomers 2-4 were also synthesized.