Oxovanadium complex-catalyzed aerobic oxidation of propargylic alcohols

A catalytic system consisting of vanadium oxyacetylacetonate [VO(acac)(2)] and 3 Angstrom molecular sieves (MS3A) in acetonitrile works effectively for the aerobic oxidation of propargylic alcohols [(RCH)-C-1-(OH)Cequivalent toCR(2)] to the corresponding carbonyl compounds under an atmospheric pressure of molecular oxygen. Although the reactivity of alpha-acetylenic alkanols (R-1 = alkyl) is lower compared to that of the alcohols of R-1 = aryl, alkenyl, and alkynyl, the use of VO(hfac)(2) as a catalyst and the addition of hexafluoroacetylacetone improve the product yield in these cases. A catalytic cycle involving a vanadium(V) alcoholate species and beta-hydrogen elimination from it has been proposed for this oxidation.