Reactivity under mechanochemical conditions: A new and more sustainable era for hypervalent iodine?

Abstract

Hypervalent iodine reagents can mediate or catalyze a wide variety of organic reactions, and have hence become important tools in the synthetic toolbox of organic chemists. Recent developments in the field include reactions under mechanochemical conditions, ranging from reports on similar or improved reactivity compared to solution-phase, to papers describing novel reaction pathways. As mechanochemistry has the potential to improve the sustainability profile of reactions by, for instance, avoiding reaction solvents and shortening reaction times, this critical review provides a sustainability comparison of mechanochemical and solution-phase reactions with iodine(III) compounds. The sustainability profiles were evaluated by comparing reaction yields, solvent properties and calculated E-factors, based on data available in the literature.Overall, the comparison provides strong support that mechanochemical hypervalent iodine reactions have improved sustainability compared to solution-phase, often with more than ten-fold decrease of waste production, and avoid a range of solvents with major issues according to the GSK solvent guide.