Oxidation of Alcohols in Continuous Flow with a Solid Phase Hypervalent Iodine Catalyst

One of the most useful transformations in the synthetic chemist arsenal is the oxidation of alcohols to their corresponding carbonyl congeners. Despite its seemingly straightforward nature, this transformative reaction predominantly relies on the use of metals or hazardous reagents, making these processes highly unsustainable. To address this challenge, we have developed a sustainable metal-free method for the oxidation of alcohols in continuous flow. Using a solid phase hypervalent iodine catalyst and nBu4HSO5 as a phase transfer catalyst and co-oxidant, primary and secondary alcohols were selectively oxidized to the corresponding carbonyl motifs. This operationally simple continuous-flow set-up is highly robust (15 cycles run without significant catalyst leaching or loss of reaction efficiency), uses green solvents, such as acetonitrile or acetic acid, and is readily scalable.