Oxovanadium reagents

The modified Sharpless reagent was also successfully applied288 for the asymmetric oxidation of a series of 1,3-dithiolanes 248 to their S-monooxides 249 (equation 134). It was observed that the optical induction on sulphur (e.e. from 68 to 83%) is not significantly affected by the substituents R1 and R2. Asymmetric oxidation of a few aryl methyl sulphides by organic hydroperoxides in the presence of a catalytic amount of the optically active Schiff base-oxovanadium(IV) complexes gave the corresponding sulphoxides with e.e. lower than 40%289. 

Dichloro(2,2,2-trifluoroethoxy)oxovanadium(v) is an effective reagent for promoting a one-electron oxidative cyclization of the silyl enol ether 1073, providing the cyclopentane fused dihydrocoumarin 1074 (Equation 420) <1998JA2658>. 

Vicinal dialkylation. The oxovanadium-induced reaction of cyclic enones with dialkylzinc reagents is followed by oxidation of the alkylzinc enolates and another C—C bond formation process, resulting in the generation of vicinal dialkylation products. 

Ryter, K. and Livinghouse, T, Dichloro(2,2,2-trifluoroethoxy)oxovanadium(V). A remarkably effective reagent for promoting one-electron oxidative cycHzation and unsymmetrical coupling of silyl enol ethers, /. Am. Chem. Soc., 120, 2658, 1998. 

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