Synthesis of Benzothiophene-3-carboxylic Esters by Palladium Iodide-Catalyzed Oxidative Cyclization–Deprotection–Alkoxycarbonylation Sequence under Aerobic Conditions

[Image: see text] A palladium-catalyzed carbonylative approach to benzothiophene-3-carboxylic esters, starting from simple and readily available building blocks [2-(methylthio)phenylacetylenes, CO, an alcohol, and O(2) (from air)], is reported. The process is catalyzed by the simple PdI(2)/KI catalytic system to give the desired products in fair to high yields (57–83%). Interestingly, the reaction also works nicely in the ionic liquid BmimBF(4) as the solvent, with the possibility to recycle the catalytic system several times without appreciable loss of activity.