Palladium-Catalyzed Synthesis of Benzothiophenes via Cross-Dehydrogenative Coupling of 4-Arylthiocoumarins and Pyrones

Benzothiophenes represent a pivotal class of sulfur heterocycles and their synthesis has attracted significant attention to generate bioactive scaffolds. Herein, we report a convergent, atom- and step-economic method for the synthesis benzothiophenes by cross-dehydrogenative coupling (CDC) of 4-arylthiocoumarins in good to excellent yields. We further demonstrate cross-dehydrogenative coupling of 4-arylthio-2-pyrones to afford alternative substitution of benzothiophenes. The presence of a labile ester carbonyl moiety provides functional handle for further functionalization by coumarin deconstruction. Most crucially, the manuscript demonstrates that the use of readily accessible templated synthesis has a significant potential for the rapid assembly of sulfur heterocycles by dehydrogenative coupling mechanism.