Oxovanadium catalysis

One should mention another, concurrent and near-contemporary methodology, also based on catalysis by an oxovanadium species. Mukaiyama and coworkers used oxovanadium (IV) complexes with the general formula OVL2 to perform epoxidations (40) A catalytic amount (4 mol%) of the complex is used. Molecular oxygen is the oxidant, under 3 atm of pressure. An alcohol in stoichiometric amount (1.5 equivalent) is introduced as a sacrificial reducer. The efficiency of the catalyst increases with a... 

Organometallic compounds asymmetric catalysis, 11, 255 chiral auxiliaries, 266 enantioselectivity, 255 see also specific compounds Organozinc chemistry, 260 amino alcohols, 261, 355 chirality amplification, 273 efficiency origins, 273 ligand acceleration, 260 molecular structures, 276 reaction mechanism, 269 transition state models, 264 turnover-limiting step, 271 Orthohydroxylation, naphthol, 230 Osmium, olefin dihydroxylation, 150 Oxametallacycle intermediates, 150, 152 Oxazaborolidines, 134 Oxazoline, 356 Oxidation amines, 155 olefins, 137, 150 reduction, 5 sulfides, 155 Oxidative addition, 5 amine isomerization, 111 hydrogen molecule, 16 Oxidative dimerization, chiral phenols, 287 Oximes, borane reduction, 135 Oxindole alkylation, 338 Oxiranes, enantioselective synthesis, 137, 289, 326, 333, 349, 361 Oxonium polymerization, 332 Oxo process, 162 Oxovanadium complexes, 220 Oxygenation, C—H bonds, 149... 

When 51V nuclear magnetic resonance (NMR) was used to follow the catalysis of trimethoxybenzene (tmb) bromination, the only vanadium species that were observed under conditions of 0.5 mM total vanadium(V) were oxodiper-oxovanadium(V) (V0(02)2 , -688 ppm), oxoperoxovanadium(V) (V0(02)+, -529 ppm), and cw-dioxovanadium(V) (-540 ppm). Within the experimental error of the integration, all of the vanadium was detected in the vanadium(V) oxidation state under turnover conditions, since the integrated signal intensity at various times throughout the reaction was equivalent to that of an equimolar solution of cis-V02+. 

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