Selective synthesis of α,β-unsaturated aldehydes from allylic alcohols using oxidatively supplied hydrogen peroxide from electrochemical two-electron water oxidation.

Selective oxidation of allylic alcohols to α,β-unsaturated aldehydes using electrochemically formed hydrogen peroxide (HO) is performed in the presence of Pt black catalyst. In this reaction, HO is oxidatively supplied from the electrochemical two-electron water oxidation (2e-WOR) of an aqueous KHCO/KCO mixed solution at a fluoride-doped tin oxide (FTO) anode. Geraniol was oxidized to the corresponding geranial in 86% yield with 99% selectivity when the appropriate amounts of Pt black catalyst with one equivalent of HO by 2e-WOR toward geraniol was employed in toluene solution at 60 °C. The HO by 2e-WOR can oxidize various kinds of allylic alcohols to give the corresponding aldehydes in 64-89% isolated yields. The detailed tuning of the amounts of Pt black and the rate of introduction of HO to the vessel allows the selective oxidation to proceed despite the low concentration of HO derived by 2e-WOR.