2-Iodoxybenzoic Acid Synthesis by Oxidation of 2-Iodobenzoic Acid at a Boron-Doped Diamond Anode

For the first time, the electrochemical synthesis of 2-iodoxybenzoic acid (IBX), a benign, well-established, popular and highly selective oxidising agent, is described. The objective of the work was to investigate the possibility of generating IBX electrochemically in aqueous solutions by using boron-doped diamond anodes. In 0.2M H2SO4 aqueous solution, 2-iodobenzoic acid (IBA) was found to be oxidised at potentials >1.6V vs. SCE, initially to 2-iodosobenzoic acid (IsBA), which was oxidised to IBX at potentials >1.8V vs. SCE. Reductions of IBX to IsBA and IsBA to IBA occurred at similar potentials of ca. -0.7V vs. SCE. The voltammetry results were confirmed by performing a series of batch electrolyses at different electrode potentials. Thus, depending on the electrode potential chosen, IBA can be oxidised anodically either to IsBA or IBX with 100% overall selectivity. The only side-reaction was O-2 generation, but charge yields did not decrease below 55% even at conversions >95%.