Maleic anhydride derivatives as catalysts for N-oxidation of pyridine using hydrogen peroxide†

Maleic anhydride derivatives were evaluated as catalysts in N-oxidation of various pyridine substrates using hydrogen peroxide (H₂O₂). Depending on the electronic properties of the pyridine substrates, pyridines with electron-donating groups reacted well with 2,3-dimethylmaleic anhydride (DMMA). In contrast, 1-cyclohexene-1, 2-dicarboxylic anhydride (CHMA) was most effective for electron-deficient pyridines. The different performance of these two anhydrides is attributed to the diacid–anhydride equilibrium, which is crucial for regenerating the peracid oxidant through an anhydride intermediate in the catalytic cycle. This approach using a catalytic amount of anhydride with H₂O₂ has the potential to replace stoichiometric amounts of percarboxylic acid as an oxidant for a broader range of organic substrates.