High production of adamantane oxygenates in propionic acid using VO(acac)2 and Eu(OTf)3 with O2

VO(acac)(2) with 1 atm O-2 catalysed the oxidation of adamantane to adamantanone, adamantanols and its esters in propionic acid at 353-393 K. Propionic acid was a more suitable solvent for the oxidation than acetic, butyric, valeric, or hexanoic acids. The maximum yield of oxygenates was 65% (3300 TON) in 360min. Adamantane solubilities and chemical stabilities of carboxylic acid were important for the oxidation; however, the coordination of carboxylic anions with the vanadium catalyst strongly affected the oxidation activity. The oxidation rate of adamantane was enhanced 3.8 times by the addition of the Eu(OTf)(3) co-catalyst. The product selectivity for various oxidations of alkane and UV-vis spectroscopic studies of V species indicated that an active species was electrophilic vanadium peroxide species coordinated propionic anion and OTf. (C) 2008 Elsevier B.V. All rights reserved.