Deoxygenation of N-heterocyclic N-oxides using isopropanol as a recyclable reductant

Abstract

The development and implementation of innovative synthetic methods that incorporate sustainable reagents and solvents are crucial aspects in both academic and industrial settings. Here, we report a novel organic photoredox-based strategy for the chemoselective deoxygenation of various functionalised N-heterocyclic N-oxides with high efficiency. The most notable feature of this catalytic process is the utilisation of the isopropanol (IPA)–acetone system of the Meerwein–Ponndorf–Verley (MPV) reaction as the redox couple matching the photocatalytic cycle, generating easily separable byproducts, namely acetone and water. Exploiting these characteristics, we have successfully conducted gram-scale deoxygenation reactions, eliminating the need for expensive and time-consuming column chromatography by using recrystallisation and distillation for product separation and purification. Furthermore, we demonstrate the practicality and sustainability of the MPV-type deoxygenation protocol by efficiently recycling both the reductant and the solvent (i.e., IPA and acetone) up to 10 times through a simple distillation process.