Manganese Dioxide and N-Hydroxyphthalimide. An Effective Catalytic System for Oxidation of Nitrotoluenes with Molecular Oxygen



The inexpensive manganese dioxide has been proven to be an efficient auxiliary for oxidizing N-hydroxyphthalimide (NHPI) to form the phthalimide N-oxyl radical via reduction and reoxidation. The combination of manganese dioxide and NHPI could catalyze effectively the oxidation of nitrotulenes by molecular oxygen. Thus, the oxidation of p-nitrotoluene with molecular oxygen (0.4 MPa) in the presence of manganese dioxide (10 mol %) and NHPI (10 mol %) in acetic acid at 110 °C for 4 h proceeded with 97 % conversion, and gave p-nitrotoluene in 89 % isolated yield.