Photo-induced C(sp3)–H functionalization of unactivated alkanes under transition-metal- and photocatalyst-free conditions

Abstract

The Giese reaction is a powerful method for C–C bond formation, but traditional approaches typically necessitate the incorporation of a leaving group on the substrate. Recent advancements combine photoredox catalysis and hydrogen atom transfer (HAT) to directly activate C(sp³)–H bonds, thereby bypassing the need for pre-functionalized substrates. However, the dependence on additional HAT reagents and expensive catalysts remains a critical challenge. Herein, we report a simple, metal-/photocatalyst-free photocatalytic system for the Giese-type reactions of unactivated alkanes by using only trace oxygen. This reaction involves the photo-excited benzylidenemalononitriles sensitizing triplet oxygen (³O₂) to generate singlet oxygen (¹O₂), which subsequently oxidizes cycloalkanes and facilitates the Giese-type reaction under mild conditions.