Phthalide synthesis through dehydrogenated lactonization of the C(sp)-H bond by photoredox catalysis

A practical and efficient method is established for the direct oxidative lactonization of the C(sp 3 )-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. An efficient method for the direct oxidative lactonization of the C(sp 3 )-H bonds of benzyl via visible-light-induced photoredox catalysis. The metal-free protocol delivers diverse phthalides using O 2 as the sole terminal oxidant at room temperature.