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

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 PdI2/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.

Automated summary

A palladium-catalyzed carbonylative approach to benzothiophene-3-carboxylic esters using readily available building blocks is reported. The reaction exhibits fair to high yields and can also be conducted in an ionic liquid solvent with the possibility of recycling the catalytic system without significant loss of activity.