Metalloporphyrin-catalyzed aerobic oxidation of 2-methoxy-4-methylphenol as a route to vanillin

• Metalloporphyrins were effective for the aerobic oxidation of 2-methoxy-4-methylphenol.
• Various reaction parameters were systematically investigated.
• Catalysis under mild conditions.
• A possible reaction mechanism was proposed.

We report the use of simple metalloporphyrins (T(p-Cl)PPMnCl, T(p-Cl)PPCo, T(p-Cl)PPFeCl, T(p-Cl)PPCu or [T(p-Cl)PPFe]2O) as a catalyst for the direct oxidation of 2-methoxy-4-methylphenol to vanillin with molecular oxygen under mild conditions. The research results showed that the type of metalloporphyrin used, catalyst loading, temperature, reaction time, the amount of NaOH, solvent, the amount of solvent and the flow rate of oxygen influenced the conversion of 2-methoxy-4-methylphenol and the selectivity of vanillin. Under the optimal conditions, the conversion of 2-methoxy-4-methylphenol was up to 87% and the selectivity of vanillin reached 74%. A possible mechanism was also proposed for the present oxidation.

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