Photoreduction synthesis of various azoxybenzenes by visible-light irradiation under continuous flow conditions

A variety of substituted azoxybenzenes can be obtained by simple photoreduction of the corresponding nitrobenzene using a flow microreactor. The yield and chemoselectivity of each azoxybenzene depends on the type and position of the substituents. In addition, the use of liquid-liquid slug flow conditions, consisting of an organic solution and a fluorous solvent like tetradecafluorohexane (TDFH) or octadecafluorooctane (ODFO), improves both the conversion and yield of this photoreduction compared to those in simple one-phase flow conditions; these results are due to synergy between the very smooth photoreduction process and the highly efficient mixing obtained under continuous-flow conditions.