Dual palladium-organophotoredox catalyzed C–H olefination–annulation of aryl carboxylic acids

Herein, we report a dual palladium-photoredox mediated tandem C-H olefination-cyclization of aryl carboxylic acids with both terminal and internal alkenes using molecular oxygen as a green oxidant. This method offers a mild and simple route for the synthesis of various isobenzofuranone derivatives. The synthetic utility of the method was demonstrated by late stage functionalization of various carboxylic acid containing drugs. Further derivatizations of the final isobenzofuranones were performed to access other important molecular scaffolds. Mechanistic studies indicated that the final cyclization step involves an oxopalladation-protodemetallation mechanism rather than a simple oxa-Michael addition commonly employed in other methodologies at elevated temperatures.