Highly efficient and metal-free oxidation of olefins by molecular oxygen under mild conditions

Highly efficient and metal-free aerobic oxidations of cyclohexene and styrene were successfully performed under mild conditions in the presence of 1,4-diamino-2,3-dichloro-anthraquinone and N-hydroxyphthalimide. When cyclohexene was oxidized, an 89% conversion and 71% selectivity for 2-cyclohexen-1-one was obtained under 0.3 MPa at 80 °C for 5 h. In the oxidation of styrene, a 77% conversion and 69% selectivity for benzaldehyde was obtained for 10 h. Furthermore, more olefins were efficiently oxidized to corresponding oxygenated products under mild conditions. All kinds of factors that affected cyclohexene oxidation were well investigated, and the possible reaction mechanism was provided.

Graphical abstractDownload full-size imageEfficient aerobic oxidations of olefins have been successfully performed under mild conditions without the need for metal catalyst. For instance, cyclohexene was oxidized with 89% conversion and 71% selectivity for 2-cyclohexen-1-one, and styrene was oxidized with 77% conversion and 69% selectivity for benzaldehyde.