Preparation of 2-methyl-1,4-naphthoquinone (vitamin K3) by catalytic oxidation of 2-methyl-1-naphthol in the presence of iron phthalocyanine supported catalyst

Iron tetrasulfophthalocyanine (FePcS) supported catalyst was prepared by covalent grafting onto amino-modified silica by a novel practical one-pot method using activation of sulfonate groups of FePcS by triphenylphosphine triflate. FePcS–SiO₂ in combination with ^tBuOOH behaved as an efficient catalyst for the oxidation of 2-methyl-1-naphthol to 2-methyl-1,4-naphthoquinone, vitamin K₃. To optimise the catalytic system, the influence of different reaction parameters on the efficiency of this oxidation has been studied. Vitamin K₃ was obtained with 59% selectivity at 96% conversion of 2-methyl-1-naphthol using only 0.5 mol% of catalyst. ¹⁸O labelling experiments indicate a non-radical mechanism for this oxidation.