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.