Copper-salen catalysts modified by ionic compounds for the oxidation of cyclohexene by oxygen

Copper-salen catalysts modified by ionic compounds were synthesized and used in the allylic oxidation of cyclohexene to 2-cyclohexen-1-ol and 2-cyclohexen-1-one with oxygen as the oxidant under mild conditions. Compared with their unmodified counterpart, the catalytic activities of these modified catalysts are improved, thereby facilitating the development of highly efficient catalysts. The type of counteranion could affect the reactivity of catalyst, which offers an opportunity to improve the catalysts via changing counteranions. The cation-anion interaction can be adjusted by different solvents, which in turn influencing the catalyst reactivity. Furthermore, these novel catalysts can be reused without sacrificing the activity. (C) 2010 Elsevier B.V. All rights reserved.