Catalytic syntheses of 2-methyl-1,4-naphthoquinone in conventional solvents and supercritical carbon dioxide

• Oxidation of 2-methylnaphthlene in acetic acid showed low selectivity.
• The gold catalyst allows an increase of the 2-methyl-1-naphthol conversion by 87%.
• The use of SC CO2 results in increasing the 2-methyl-1-naphthol conversion by 10–15%.

This paper reports a comparison of commonly used methods of the 2-methyl-1,4-naphthoquinone syntheses and possible application of supercritical (SC) carbon dioxide (CO2) as a “green solvent” for this process. The 2-methyl-1,4-naphthoquinone syntheses were carried out by two main reaction routes using 2-methylnaphthalene or 2-methyl-1-naphthol as substrates in the presence or absence of catalysts in common solvents and the SC CO2 media. The influence of SC CO2 on the above reactions is discussed.