Fe(NO3)3/NHPI-mediated co-oxidation of ketones and toluene for Baeyer-Villiger reaction with molecular oxygen

Abstract

When oxygen is used as the oxidant in Baeyer-Villiger reaction, the excessive benzaldehyde is usually added as the sacrificial promoter, and the high price of benzaldehyde inhibits the development of this method. In this work, toluene, a much more feasible reagent comparing to benzaldehyde, was reported as a new drive for Baeyer-Villiger oxidation for the first time. Through the optimization of the metallic catalysts and solvents, the lactones are obtained accompanied with good yields of valuable benzaldehyde and benzoic acid under molecular oxygen atmosphere. Fe(NO₃)₃·9 H₂O and N-hydroxyphthalimide were used as the efficient catalysts which were compatible for the one-pot oxidation of toluene and cyclic ketones. The process analysis suggested that the benzoic peroxyacid generated from the oxidation of toluene is the dominant oxidant for the Baeyer-Villiger reaction of cyclic ketones. The intermediate analysis, ¹⁸O₂ labeling experiment and oxygen-free experiment revealed the critical role of O₂ and NO₃^- in the co-oxidation.