Synthesis of Novel Benzothiophene Derivatives via Cyclization Reactions

The Sonogashira cross coupling reaction of 2-bromo-5-(4-methoxyphenyl)thiophene and 1-ethynyl-2-(methylsulfanyl)benzene gave 2-(4-methoxyphenyl)-5-{[2-(methylsulfanyl)phenyl]ethynyl}thiophene which was subjected to electrophilic cyclization by the action of iodine to obtain 3-iodo-2-[5-(4-methoxyphenyl)thiophen-2-yl]-1-benzothiophene. Stille and Sonogashira coupling reactions of the latter afforded a series of new 3-substituted 2-[5-(4-methoxyphenyl)thiophen-2-yl]-1-benzothiophene derivatives of potential pharmacological interest.