Phthalide synthesis through dehydrogenated lactonization of the C(sp3)–H bond by photoredox catalysis

A practical and efficient method is established for the direct oxidative lactonization of the C(sp3)–H bonds relying on visible-light-induced photoredox catalysis. This protocol expediently allows the delivery of diverse phthalides using oxygen as the sole terminal oxidant under metal-free conditions at room temperature. Notably, the choice of an appropriate hydrogen atom transfer (HAT) cocatalyst is revealed to be critical for the success of this process.