Multistep Synthesis of Organic Selenides under Visible Light Irradiation: A Continuous-Flow Approach

The potential application of multistep continuous-flow systems has had a great impact on the syntheses of active pharmaceutical ingredients, natural products, and commodity chemicals. In this report, the highly efficient combination of a chemical reduction and a photochemical Csp2 –H activation reaction for selenylation of biologically relevant electron-rich arenes was achieved by means of a continuous-flow process. First, the reduction of alkyl and aryl selenocyanates by Rongalite was achieved giving the corresponding diselenides; second, the photoactivation of the Se–Se bond resulted in the selenylation of electron-rich arenes, both steps from good to excellent yields. In all cases, the reaction time was shortened, and isolated yields were improved when compared to batch reaction conditions. Furthermore, connecting both reactions in a multistep continuous-flow sequence was possible even when reductive and photooxidative transformations were coupled.