AN EFFICIENT AEROBIC OXIDATION OF ISOBUTANE TO T-BUTYL ALCOHOL BY N-HYDROXYPHTHALIMIDE COMBINED WITH CO(II) SPECIES

Highly selective aerobic oxidation of isobutane to t-butyl alcohol was successfully achieved by the use of a radical catalyst, N-hydroxyphth alimide (NHPI) in the presence of Co(II) salt under relatively mild co nditions. The oxidation of isobutane by NHPI combined with Co(acac)(2) under a pressure of air (10 atm) in benzonitrile at 100 degrees C gav e t-butyl alcohol in high yield (84%) along with acetone (13%). The re action is thought to proceed via hydrogen abstraction from isobutane b y the phthalimidooxyl radical (PINO), which seems to be a key active s pecies. The formation of acetone can be explained by a partial beta-sc ission of the t-butoxy radical, generated from the redox decomposition of t-butyl hydroperoxide by cobalt ion. Alkyl-substituted butanes and pentanes were difficult to be oxidized selectively under these condit ions because of easy degradation to smaller fragments of the resulting alkoxyl radical intermediates.