Oxidation Of 2,4-dimethylnitrobenzene Through Phase Transfer Catalysis

The preparation of 3-methyl-4-nitrobenzoic acid, an intermediate of Telmisartan, from 2,4-dimethylnitrobenzene in liquid phase was studied. In neutral system, 2,4-dimethylnitrobenzene was oxidized selectively under heterogeneous conditions by using tetrabutylammonium bromide as phase transfer catalyst, potassium permanganate as oxidant. The yield of 3-methyl-4-nitrobenzoic acid was 54%, compared with the literature yield of 27%. The structure and purity of the product were determined with NMR and HPLC. The reaction parameters such as reaction temperature, reaction time, catalyst etc were optimized. The factors influencing the selectivity of the oxidation and the mechanisms of the phase transfer catalysis were discussed according to experimental results.