Effect of Incubation of CO2 and Lewis Acid on the Generation of Toluic Acid from Toluene and CO2

Abstract

p-Toluic acid is produced by reacting Lewis acid (1), CO2 (2), and toluene (3) at milder conditions. The order of addition of reactants is found to be able to change the course of the reaction toward the desired product and therefore must be 1, 2, and 3. Reaction occurs through in situ formation of a Lewis acid:CO2 adduct created by incubating CO2 and Lewis acid for 1 h prior to the addition of toluene. The order of addition led the reaction to occur with anhydrous Al2Cl6 and a few other Lewis acids than only anhydrous Al2Cl6 in the usual way of addition 2, 3, and 1. Spectacularly CuBr2 produces p-toluic acid as major product when incubated with CO2 at 57 bar and 80 °C prior to addition of toluene whereas bromotoluene is a major product when added with toluene and then pressurized with CO2 at the same temperature and pressure.