Vanadyl acetylacetonate oxidation

In presence of triphenyl phosphite or tri(4-methyl 6-f-butylphenyl) phosphite, (6) also acts as an oxidation inhibitor for polyenes. The complexes formed have not been studied, but the effect is attributed to termination of radical chains and the complexes are more active than the phosphites alone.29 Vanadyl acetylacetonate is also employed as a hardener for unsaturated polyesters.30... 

Fig. 32 Vanadyl acetylacetonate-catalyzed oxidative ring expansion of bicyclic cyclopropanols...

However, since the catalytic system is homogenous, carefully adjusted reaction conditions were needed to circumvent the second nonselective catalytic cycle. Slow addition of the alkene and the hydrogen peroxide was necessary to obtain good enantioselectivities (Table 6) [13]. Recently, Backvall s group reported that the Cinchona alkaloid ligand participated in the reoxidation process and took the role of NMO in the catalytic cycle [15]. Versions of the triple catalytic system with vanadyl acetylacetonate replacing the flavin analogue [16] or m-CPBA as the terminal oxidant [17] have been developed and successfully applied to racemic dihydroxylation reactions. 

In addition, the polymerization could be performed catalytically in the presence of air. For example, 4,4 -bis(naphthoxy)diphenyl sulfone was polymerized using atmospheric oxygen as the oxidant, 1 mol% vanadyl-acetylacetonate and 10% triflic acid in CHC13 [Eq. (63)] [211]. 

Vanadium(IV) Schiffsbase complexes derived from P-aminoalcohols 7.62 and vanadyl acetylacetonate have been used to oxidize different substrates to chiral sulfoxides. 

For the synthesis of natural products containing oxirane rings, it is desirable to prepare not only the correct diastereomers but also the proper enantiomers. To this effect, different chiral oxidants were tested tert-hutyl hydroperoxide and chiral hydroxamic acids as ligands to vanadyl acetylacetonate [1031] and especially tertAmtyX hydroperoxide, titanium tetra-... 

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). 

Van Doorslaer S, Segura Y, Cool P (2004) Structural investigation of vanadyl-acetylacetonate-containing precursors of TiO -VOx mixed oxides on SBA-15. J Phys Chem B 108 19404-19412... 

Oxidation of j8-dicarbonyl compounds by f-butyl hydroperoxide in the presence of vanadyl acetylacetonate [VO(acac)2] in benzene results in decomposition of the carbon skeleton, via intermediate trioxo derivatives." ... 

The asymmetric synthesis of florfenicol (104) from the oxidation of 4-methylthiobenzaldehyde by TBHP in the presence of Yamamoto s vanadium catalyst resulted in 37% overall yield intermediate formation of aUyUc alcohol (105) and its epoxidation to (25, 35)-epoxide (106) in 75% yield and 90% ee was involved. TBHP oxidation of jS-dicarbonyls in the presence of vanadyl acetylacetonate in benzene involved the activated methylene group in formation of intermediate trioxo derivatives and is accompanied by decomposition of the carbon skeleton... 

The oxidative polymerization of diphenyl disulfide was carried out in the presence of a strong acid by electrolysis (198) and by reaction with Lewis acids such as SbCls (199-201) or quinones such as 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (202-205). VO catalysts such as vanadyl acetylacetonate with O2 have also been used for the oxidative polymerization (206-208), and the catalytic reaction mechanism involving four-electron reduction of O2 has been discussed (209-215). 

The oxidized electron transfer mediator (ETMox). namely the peroxo complexes of methyltrioxorhenium (MTO) and vanadyl acetylacetonate [VO(acac)2] and flavin hydroperoxide, generated from its reduced form (Figure 1.1) and H2O2, recycles the N-methylmorpholine (NMM) to N-methylmorpholine N-oxide (NMO), which in turn reoxidizes the Os(VI) to Os(VIII). While the use of hydrogen peroxide as oxidant without any electron transfer mediators is inefficient and nonselective, various alkenes were oxidized to diols in good to excellent yields employing this mild triple catalytic system (Scheme 1.2). 

In the present contribution, we describe the preparations of several binary transition metal tosylates directly from the metal and p-toluenesulfonic acid under an inert atmosphere. This method is easy to carry out, and affords products that are completely free of contaminating counterions. The presence of excess metal provides a reducing environment, so that divalent products are obtained for all first-row transition metals except for Ti and V, which form trivalent products under these reaction conditions. The Cr° salt may be converted to Cr (OTs)3 by air oxidation in the presence of excess p-toluenesulfonic acid. Tosylate salts of Ti, V, Fe, and Cs can also be prepared by treatment of the corresponding metal chloride with p-toluenesulfonic acid, and a vanadyl salt has been prepared by similar treatment of vanadyl acetylacetonate. 

Group 5 metal-promoted oxidations epoxidations using vanadyl acetylacetonate... 

Computational studies on the mechanistic features of the oxidation of ethylene and 1,3-butadiene with HP, catalysed by vanadyl acetylacetonate, showed that under thermodynamic control, no selectivity is observed between epoxidation and double bond oxidative cleavage. Under kinetic control, however, in both systems, the double bond oxidative cleavage is the favoured path. ... 

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