Palladium-Catalyzed Domino Heteroarylation of Thioamides: A Simple Route to Benzothieno[2,3-b]quinolones

Domino reactions are essential for advancing organic synthesis. This study introduces novel thioamide-based precursors for a palladium-catalyzed selective domino heteroarylation process. The method efficiently produces benzothieno[2,3-b]quinolones with yields ranging from moderate to very good. By employing aryl chlorides, the efficiency of the domino hetero-annulation process is comparable to that of aryl bromides. Executing a one-pot, two-step reaction also delivered a single domino product with high selectivity. The strategy involved fine-tuning substituent reactivity, utilizing electron-rich arenes, and forming metallocycles with nucleophilic sulfur, consistently yielding a single product. The proposed mechanism is corroborated by mechanistic studies.