A Green Process for Oxidation of p-Nitrotoluene Catalyzed by Metalloporphyrins under Mild Conditions

A novel synthetic technology of p -nitrobenzoic acid has been investigated with dioxygen by using metalloporphyrins RTPPM III Cl (M = Fe, Co, Mn) as biomimetic catalysts. Oxidation of p -nitrotoluene to p -nitrobenzoic acid under 2.0 MPa of O 2 in the presence of a microamount of metalloporphyrins (RTPPM III Cl) at 55 °C was achieved with the highest (up to 90.4%) yield. Further research results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of metalloporphyrins. For the metalloporphyrins with the same center metal ions, the greater the electron-withdrawing degree of groups in the porphyrin ring, the higher the catalytic activities of the metalloporphyrins. The catalytic activities for metalloporphyrins with different center metal ions followed the order RTPPMn III Cl >RTPP Fe III Cl > RTPP Co III Cl.