Visible-Light-Mediated Intramolecular Lactonization of Benzylic C(sp3)–H Bonds Promoted by DDQ and tert-Butyl Nitrite

Abstract A functionalization of benzylic C(sp3)–H bonds was established through a mild metal-free intramolecular lactonization protocol in the presence of DDQ/tert-butyl nitrite as photocatalysts, allowing practical and low-cost access to a series of phthalide products in moderate to excellent yields. Compared with many existing methodologies, this visible-light-driven process exhibits an excellent substrate scope and fascinating features, including the formation of water as the sole byproduct, an abundant and green energy source, commercially available catalysts, and room-temperature reaction. Finally, detailed mechanistic investigations clearly revealed the role of the photocatalysts and molecular oxygen.