Aerobic oxidation of organic compounds catalyzed by vanadium compounds

Aerobic oxidation of alpha-hydroxy ketones catalyzed by dichloroethoxyoxovanadium in ethanol causes a carbon-carbon bond cleavage that produces diesters or diketones. This reaction is highly chemoselective, and disecondary glycols do not react at all. However, ditertiary glycols effectively react with dichloroethoxyoxovanadium or trichlorooxovanadium to provide the corresponding ketones. Aerobic oxidation of alpha-hydroxy ketones catalyzed by dichloroethoxyoxovanadium or trichlorooxovanadium in aprotic solvents almost quantitatively affords the corresponding alpha-diketones. The reaction of tertiary cyclopropanol compounds with vanadyl acetylacetonate under an oxygen atmosphere causes fragmentation of the cyclopropane moiety to produce beta-hydroxy ketones and beta-diketones. For the 6-substituted bicyclo[4.1.0]heptanol derivatives, the endoperoxides are also obtained together with beta-hydroxy ketones. Conversely, 2-ethoxycarbonylcyclopropyl silyl ethers produce gamma-oxocarboxylate derivatives given the same reaction conditions. Monothioacetals are easily deprotected into carbonyls using a catalytic amount of trichlorooxovanadium in 2,2,2-trifluoroethanol under an oxygen atmosphere. Thiols are converted into the corresponding disulfides by the aerobic oxidation catalyzed by trichlorooxovanadium in the presence of molecular sieves 3A. Polymer-supported vanadium compounds are synthesized by the reaction of vanadium oxytrichloride with polymers bearing hydroxyl moieties. The catalyst prepared from TentaGel S OH was highly active and reusable for the aerobic oxidations. (C) 2011 Elsevier B.V. All rights reserved.