Direct catalyst-free photochemical C(sp3)–H bond functionalization of cyclic ethers with Michael acceptors

Photochemical functionalization of C(sp 3 )-H bonds provides an important tool in the arsenal of organic chemists to promote valuable transformations. Exploring the capabilities and limitations of light-driven reactions, in this study, we present a catalyst-free protocol for the activation of the α -C-H bond of five-membered cyclic ethers by employing 390 nm LED irradiation. A variety of Michael acceptors participated in the reaction, leading to the desired products in moderate to high yields. Mechanistic studies, through High Resolution Mass Spectrometry (HRMS) and on/off experiments, proved the necessity of light for the reaction to occur, while also providing a plausible reaction mechanism. • Direct and catalyst-free protocol for the α-oxy C(sp 3 )-H functionalization of cyclic ethers. • Activation of five-membered cyclic ethers by employing 390 nm LED irradiation and their reaction with Michael acceptors (maleates and maleimides). • Short reaction times and necessity of continuous irradiation.