Visible-Light-Driven Photocatalytic Cascade Multioxidation: A Route to α-Sulfinylphthalides.

The integration of direct C(sp3)-H functionalization with tandem reactions offers a strategy for the synthesis of complex, high-value fine chemicals from basic chemical feedstocks. This paper presents an efficient synthetic pathway for the olefinic difunctionalization of o-methylstyrenes using thiophenols, followed by oxidative dehydrogenative lactonization catalyzed by LaBr3 under visible light irradiation. This approach enables the facile synthesis of a wide range of α-sulfinylphthalides with moderate diastereoselectivity. Notably, the reaction does not require additional photosensitizers or strong oxidants; mild conditions suffice under an oxygen atmosphere. Mechanistic studies and control experiments have confirmed the essential role of LaBr3 in this process.