C–H Functionalization via photo- and electrochemistry in flow: a review

Abstract

The direct activation and functionalization of C–H bonds represent a cornerstone of modern synthetic chemistry, aiming at developing step- and atom-economical routes to complex molecules. However, traditional methods often rely on stoichiometric oxidants or harsh conditions, leading to challenges in sustainability and selectivity. Photo- and electrochemistry have attracted increasing research interests as they use light or electricity as traceless reagents and also possess the advantages of simple operation and tunable selectivity. Flow technology further enables precise reaction control over multistep transformations, improved reaction reproducibility, enhanced safety, and the easy integration of photochemical and electrochemical steps. Taking advantage of continuous-flow photo- and electrochemistry can help chemists expand the chemical space available for C–H functionalization. This review highlights the application of continuous-flow strategies in C–H functionalization and showcases photo/electrochemical examples with different functional group transformations or reaction patterns for both C(sp³)–H and C(sp²)–H bonds in flow systems. By highlighting the enhanced performance, scalability, and mechanistic insights afforded by flow chemistry, we aim to demonstrate the potential of this synergistic platform and inspire its broader application in the C–H functionalization field as well as in chemical synthesis and pharmaceutical manufacturing.