Use of Biomass Glycerol as a Reducing Agent for Photocatalytic Deprotection of Pyridine N‐Oxides in an Aqueous Suspension of Titanium(IV) Oxide

Deprotection of pyridine N-oxides under a mild condition with an inexpensive and environmentally friendly reducing reagent is important. The use of biomass waste as the reducing reagent, water as the solvent and solar light as the energy source is one of the most promising approaches with minimal impact on the environment. A TiO2 photocatalyst and glycerol successfully combine these items and stoichiometric deprotection of pyridine N-oxide (PyNO) with a minimal amount of glycerol (PyNO:glycerol= 7:1) was achieved, with only CO2 being produced as the final oxidation product of glycerol. The deprotection of PyNO is thermally accelerated. Under solar light, the temperature of the reaction system increased to 40-50oC and PyNO was also quantitatively deprotected, indicating that solar energy, i.e., UV light and thermal energy, can be effectively used. The results provide a new approach in the fields of organic chemistry and medical chemistry using biomass waste and solar light.