Copper-Promoted Intramolecular Oxidative Dehydrogenation for Synthesizing Dihydroisocoumarins and Isocoumarins

Isocoumarins and dihydroisocoumarins are important skeletons with a wide range of biological activities, such as anti-bacterial, anti-allergy, anti-fungal, anti-tumor, and anti-HIV properties. Herein, we demonstrated divergent syntheses of isocoumarins and 3,4-dihydroisocoumarins by intramolecular dehydrogenative cyclization of 2-(3-oxobutyl) benzoic acids. This transformation undergoes Csp(3)–H bonds and O–H bonds coupling in air using copper salt. The reactions may undergo free radical process.