The Liquid-Phase Oxidation of p-Methoxytoluene to p-Anisaldehyde with Co(OAc)2/Ce(OAc)3/Cr(OAc)3 Catalyst

The liquid-phase oxidation of p-methoxy toluene to p-anisaldehyde in the presence of Co based catalysts has been studied. With Co(OAc)2 alone in acetic acid as a solvent, only a trace amount of p-anisaldehyde could be obtained; however, upon the addition of a second metal salt (e.g., Mn(OAc)2 or Ce(OAc)3) a considerable improvement in the yield (up to 60%) was observed. The synergism of Co and the second component as well as the optimization of the reaction conditions were investigated. Co(OAc)2–Ce(OAc)3–Cr(OAc)3 (3:1:2) was finally found to be the most effective catalytic system, which gave a 76% yield of p-anisaldehyde under 3 atm O2 at 110° for 3 h.