Vanadyl acetylacetonate allylic oxidation

Treatment of 762 with allyl bromide and sodium hydride provides in 82% yield the C2-symmetric pyrrolidine 776. Chemoselective N-oxidation with er butylhydroperoxide in the presence of vanadyl acetylacetonate affords in 75% yield the N-oxide 111 which, when treated with LDA, forms a benzylideneazomethine ylid (having the Z-configuration) that undergoes an intramolecular 1,3-dipolar cycloaddition to afford the e isolable product in 35% yield (Scheme 170). 

Catalyst in Oxidation Reactions. DBTO has been used as a catalyst in Fe -mediated oxidation of thiols to disulfides, even though Tri-n-butyl(methoxy)stannane seems to be better suited for this purpose. Epoxidation of terminal alkenes in a two-phase system (chloroform-water) containing H202/ammonium molyb-date/DBTO has also been reported. A combination of DBTO and t-Butyl Hydroperoxide oxidizes allylic alcohols with moderate regio- and stereoselectivity. Tri- and tetrasubstituted double bonds are most easily oxidized and the selectivities are comparable to those of the corresponding Vanadyl Bis(acetylacetonate) mediated reactions. 

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