Iron(II) and copper(II) phthalocyanine-catalyzed synthesis of 2-nitro-4-methylsulfonylbenzoic acid under mild conditions

A novel method was developed to produce 2-nitro-4-methylsulfonylbenzoic acid (NMSBA) from the oxidation of 2-nitro-4-methylsulfonyltoluene (NMST) by oxygen catalyzed by iron(II) phthalocyanine (FePc) and copper(II) phthalocyanine (CuPc). The order of activity for oxidation of NMST was found to be: FePc > CuPc. Meanwhile, major reaction parameters such as concentrations of catalyst and NaOH, reaction temperature and oxygen pressure have been investigated. Through optimization of the reaction parameters, the highest yield of NMSBA and conversion of NMST (up to 53%, 89.3%, respectively) were achieved with oxygen (2.0 MPa), FePc (), NaOH (), in methanol at 55 for 8 h. A plausible mechanism for this catalytic process is proposed which involved deprotonation and radical pathways.