Vanadyl acetylacetonate catalyst

Sol in acet, tetrahydrofuran and eth acetate, si sol in n-heptane and methanol v si sol in toluene and w. Prepn of the initial polymer is from a dioxane soln at 50° of 2.0 equiv mol wts each of the monomers using either 1.5 equiv wt % of boron trifluoride etherate or 2.0 equiv wt % of vanadyl acetylacetonate as a catalyst to enhance the polymerization rate. Complete polymerization or gel is accomplished in about 70 hrs at 50°. The reaction rate is further enhanced by the addition of 0.072 equiv wt % of the isocyanate monomer after the initial reaction, resulting in gelation after 40 hrs at 50°. The hot dioxane soluble product is w pptd, vacuum steam-distd and dried. Post polymerization nitration of the polymer is accomplished with 100% nitric acid at 65°... 

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). 

Table 7). In an early application, VF was polymerized with a catalyst composed of diethylalnminnm bromide-titanium tetrachloride-carbon tetrachloride (82). A Ziegler-Natta system based on vanadyl acetylacetonate and AIR(OR)Cl compounds gives good yields (82) at polymerization temperatures up to 50°C. A modified catalyst prepared from vanadium oxytrichloride, triisobutylaluminum, and tetrahydrofnran was foimd to be the most effective Ziegler-Natta system... 

The most direct way to prepare VO(acac)2 is by the reaction of vanadyl sulfate with a source of the ligand. Vanadium(V), such as V205, can be reduced to vanadium(IV) by ethanol solvent in the presence of sulfuric acid. Reaction with acetylacetone in sodium carbonate yields the desired product. The synthesis we will use produces the complex in high yield directly in a system that can visually shed light on the active catalyst species in the epoxidation of olefins, Figure 9.4. 

Isomerization of Allylic Alcohols and Formation of 1-Halo-1-alkynes. Isomerization of primary and secondary allylic alcohols to tertiary isomers proceeds in CH2CI2 at 25 °C in the presence of a catalyst that is prepared in situ by activation of vanadyl bis(acetylacetonate) or Mo02(acac)2 with (1) (eq 3). On the other hand, terminal alkynes react with (1) in the presence of copper or zinc halides in THF at —15 °C to afford terminal 1-halo-1-alkynes in 40-85% yields. By the same method, 1-cyano-l-alkynes are obtained in 65% yield by use of copper cyanide. 

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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