A cooperation of ceric ammonium nitrate and N-hydroxyphthalimide in the aerobic oxidation from ketones to lactones/esters: Catalytic characterization and mechanistic investigation

When molecular oxygen is employed as the oxidant in the Baeyer-Villiger reaction, the addition of an excess amount of sacrificial aldehyde/alcohol to generate peroxyacids or peroxides in situ is the most frequently adopted strategy. In this work, we report a sacrifice-free approach to lactone/esters from ketones using molecular oxygen as the oxidant, in which cerium ammonium nitrate and N -hydroxyphthalimide were utilized as the catalysts with a good tolerance to cyclic and aromatic ketones. Experiments have shown that the presence of α-hydrogens in ketone compounds is a critical condition for the reaction, and the 2 H labeling experiments demonstrated that the oxidation is initiated via the deprivation of the α-hydrogen of ketone by phthalimide N -oxy radical (PINO), which is significantly different from the Criegee-Intermediate mechanism of traditional BV reaction. And the 18 O labeling experiment suggested that NO 3 − participates in the oxidation of the carbonyl compounds and NO 3 − could be regenerated by molecular oxygen. The redox process of cerium and the structure of the catalytic complex were also illustrated by the EPR and XRD characterization. Meanwhile, cerium ammonium nitrate was proved to be capable recycle although its reactivity was decreased after two cycles. The unprecedented mechanism for the synthesis of lactone/ester was hoped to provide a new prospect in the academic study and industrial manufacture.