Oxidative lactonization of C(sp3)-H bond in methyl aromatic alcohols enabled by proton-coupled electron transfer

Direct functionalization of inert C(sp 3 )-H bonds in pharmaceutically significant compounds is very important in modern synthetic organic chemistry. In this article, we disclose a practical and efficient method for the oxidative lactonization of benzylic C(sp 3 )-H bonds enabled by the synergistic interactions of organic dye-type rose bengal, n -Bu 4 N·Br, O 2 and Na 2 HPO 4 under visible light irradiation. This reaction does not require transition metal catalysts or strong oxidants. A range of structurally diverse phthalides has been synthesized with excellent selectivity and high functional group compatibility. The late-stage application of this reaction to the preparation of structurally complex phthalides demonstrates its synthetic utility.