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

Abstract

Functionalization of the benzylic C(sp3)-H bond was established through a mild, metal-free intramolecular lactonization protocol in the presence of DDQ/TBN photocatalysis, allowing practical and low-cost access to a series of phthalide products in moderate to excellent yields. Compared to many existing methodologies, this visible-light-driven process exhibited excellent substrate scope and fascinating features consisting of water as the sole byproduct, abundant and green energy source, commercially available catalysts, and room temperature. Finally, detailed mech-anistic investigations clearly revealed the role of photocatalysts and molecular oxygen.