Vanadium oxytrifluoride

The intermolecular examples of synthetic value are self-couplings, e.g. formation of the dimer (43) from benzylsesamol, in 85% yield using vanadium oxytrifluoride preparation of the biaryl (44 95%), from 4-methylveratrole, employing iron(III) chloride supported on silica and synthesis of 4,4 -dimeth-oxybiphenyl (69%) fr om anisole by oxidation with thallium(III) trifluoroacetate in the presence of catalytic palladium(II) acetate. This approach has been used in a natural product synthesis. The dimers (45) and (46) were prepared from appropriate derivatives of gallic acid, and transformed into schizandrin C (47) and an isomer respectively. ... 

The use of vanadium(V) salts in oxidative coupling reactions was prompted by the work of Funk et al. who recognized the ability of vanadium oxytrichloride to form phenoxyvanadium complexes with phenols [llO]. As it was shown by Schwartz et al., such complexes can be isolated and used for oxidative couplings [111]. Vanadium oxytrifluoride, a superior reagent [112] was found to be effective not only with free phenols but also with phenol ethers revealing the non-phenolic mechanism of this oxidation [113]. The method was successfully adapted to the oxidative macrocyclisation of a vancomycin subunit [114]. 

OXIDATIVE COUPLING Cupric acetate. Potassium ferricyanide. Silver oxide. Thallium-(111) trifluoroacetate. Vanadium oxytrifluoride. 

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