Efficient aerobic oxidation of hydrocarbons with O2 catalyzed by DDQ/NHPI

BACKGROUND: Organocatalysis, a promising strategy for the oxidation of organic compounds, does not involve the use of a catalytic metal. In this work, an efficient organocatalyst system consisting of 2,3-dichloro-5,6-dicyano-benzoquinone (DDQ) and N-hydroxyphthalimide (NHPI) was studied. RESULTS: 72.2% conversion with 92.3% selectivity for acetophenone was obtained in ethylbenzene oxygenation catalyzed by DDQ/NHPI under 0.3 MPa of molecular oxygen at 80 °C for 10 h. In addition, other hydrocarbons were also oxidized with high efficiency using this catalyst system. UV/Vis spectroscopy of the catalytic system indicated that DDQ accelerated the generation of free radical phthalimido-N-oxyl (PINO) by abstracting a hydrogen atom from NHPI. CONCLUSION: An efficient organocatalyst system consisting of DDQ and NHPI for selective oxidation of hydrocarbons to corresponding ketones with molecular oxygen as oxidant is reported. DDQ promoted the generation of PINO from NHPI, and the oxidation reaction was accelerated via PINO. This organocatalyst system should be useful for the design of highly selective catalysts for hydrocarbon oxidation. Copyright © 2010 Society of Chemical Industry