Olefin conversion epoxidation

Olefin isomerization can be catalyzed by a number of catalysts such as molybdenum hexacarbonyl [13939-06-5] Mo(CO)g. This compound has also been found to catalyze the photopolymerization of vinyl monomers, the cyclization of olefins, the epoxidation of alkenes and peroxo species, the conversion of isocyanates to carbodiimides, etc. Rhodium carbonylhydrotris(triphenylphosphine) [17185-29-4] RhH(CO)(P(CgH )2)3, is a multifunctional catalyst which accelerates the isomerization and hydroformylation of alkenes. 

Run no. Catalyst Reactant Initial/ before H202 addition pH After H202 addition At die end of die reaction TOF Olefin conversion (mol%) h2o2 efficiency Epoxide selectivity (mol%)... 

Supported iron porphyrins are less reactive than the corresponding manganese derivatives in the PhIO epoxidation of cyclooctene. 80% of olefin conversion was reached with MnBrgTMPS-PVP in 2 h, whereas only 10% was obtained with FeBrgTMPS-PVP in 6 h. 

By analogy between the oxo forms of vanadium(V) and iron(IV), the latter being the active species in oxidations by cytochrome P-450, the system constituted by vanadium oxide as the catalyst, and t-butylhydro-peroxide, as the oxidant, gives good results in the conversion of olefins to the corresponding epoxides. With the supported "clayniac" catalyst, in the presence of i-butyraldehyde as a sacrificial reducer, olefins are epoxidized in good yields by compressed air at room temperature, in a convenient procedure. 

Results on epoxidation of cyclohexene with H2O2 with freshly prepared catalysts are given in Table 2. With Mo blue, exchanged on Mg,Al-LDH, the olefin conversion is low, even if all peroxide is consumed within 4 h. Upon addition of the H2O2 to the reaction mixture, the suspended catalyst has the yellow hue of the Movl form of the isopolyacid. However, the suspension soon turns brick red. This color is characteristic for tetraperoxomolybdate Mo(02)42 [17], This indicates that the isopolyacid structure degrades rapidly, with formation of Mo monomers. Peroxo complexes such as Mo(0 )42 or particularly MoO(C>2)32 are known to decompose with formation of 02 the overall process is a decomposition of two molecules of H2O2 into water and C>2 [18] ... 

Conversion of olefins into epoxides has been achieved in a great ifnbfiT of cases through halohydrin intermediates generated by " kiition of hypoholous acids across the olefiiuc double bond (Eq, 127). 

Several peroxy acids are need in the conversion of olefins into epoxides. Their properties and preparations have been described by Swem.1<78>1878 Included among them are performio acid, peracetic arid, parbenzoio acid, monoperphthalic acid, and percamphoric acid, Mere recently trifluoroperacetic acid has attained some promi-nenee.S01>1I4fl-1778 Certain desirable features have been discovered in y-nitroperbenzoic arid as well.1 ... 

A one-sided attachment of a vinyl-functionalized salen monomer to an MCM-41 material was reported by Janssen (95). In the epoxidation of 1-phenylcyclohexene with PhIO in acetonitrile, the Mn-functionalized structure 7g gave an ee of 75%, which is the same as for the soluble Jacobsen complex and considerably higher than that obtained with 7f. Morever, the chemoselectivity, the olefin conversion, and the enantioselectivity remained unchanged over four consecutive cycles. 

Olefin Temperature (°C) Time (min) Hydrogen peroxide (% conversion) Epoxide yield (%)... 

Uses. The reagent is used in the same way as perbenzoic acid, mainly for the conversion of olefins into epoxides. However, as compared to perbenzoic acid in chloroform, perphthalic acid in ether has the advantage that the course of a reaction can be followed by noting the size of the precipitate of phthalic acid formed, or by filtering the solution and seeing if any more phthalic acid separates. One can note also if a solution stored in a refrigerator in a stoppered flask deteriorates on standing. 

In general, since epoxidation involves electrophilic reagents, double bonds with electron-donating substituents are more reactive. Thus, internal or cyclic alkenes give higher conversions than do terminal olefins. Conversely, in general, electron-withdrawing substituents increase the activity of electrophilic catalysts. 

The best epoxidation results thus far were reported by Beller and coworkers using an in situ generated epoxidation catalyst capable of up to 100% conversion of a range of aryl olefins to epoxides (Table 18.2) [44]. They used a combination of... 

The use of polypyrazolylborate copper(I) complexes as catalysts in the conversion of olefins into epoxides 01JOM(617-618)110. 

Manipulation of the carbonyl function to epoxide 3 was accomplished by conversion to the tosylhydrazone, Shapiro olefination, and epoxidation.The latter step occurred with high ster-eocontrol, as did the epoxide ring opening with acidic methanol. Oxidation to ketone 4 was then performed, and from this product the desired derivative 5 was obtained by known procedures. 

Similar polymeric electrolysis conditions are able. In the presence of water, to effect the conversion of olefins Into epoxides (68), In this case, choice of an anion exchange resin was crucial (Amberllte IRA-900 br)). The electrochemical efficiency is substantially lower (due to the competing electrolysis of water) but yields are high. Unsaturated carbonyl compounds do not react. 

The most widely used reaction in this category is the conversion of olefins to epoxides. In most cases, one of several peroxycarboxylic acids is used to effect oxidation. m-Chloroperoxybenzoic acid, which is commercially available or readily prepared and is a quite stable solid, is the most popular reagent. Peroxyacetic acid, peroxybenzoic acid, peroxytrifluoroacetic acid, and others, however, have also been used frequently. 

Torii S, Uneyama K, Tanaka H, Yamanaka Y, Yasuda T, Ono M, Kohmoto Y (1981) Efficient conversion of olefins into epoxides, bromohydrins, and dibromides with sodium bromide in water-organic solvent electrolysis. J Org Chem 48 3312-3315... 

The 9 — 15 fragment was prepared by a similar route. Once again Sharpless kinetic resolution method was applied, but in the opposite sense, i.e., at 29% conversion a mixture of the racemic olefin educt with the virtually pure epoxide stereoisomer was obtained. On acid-catalysed epoxide opening and lactonization the stereocentre C-12 was inverted, and the pure dihydroxy lactone was isolated. This was methylated, protected as the acetonide, reduced to the lactol, protected by Wittig olefination and silylation, and finally ozonolysed to give the desired aldehyde. 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

The primary determinant of catalyst surface area is the support surface area, except in the case of certain catalysts where extremely fine dispersions of active material are obtained. As a rule, catalysts intended for catalytic conversions utilizing hydrogen, eg, hydrogenation, hydrodesulfurization, and hydrodenitrogenation, can utilize high surface area supports, whereas those intended for selective oxidation, eg, olefin epoxidation, require low surface area supports to avoid troublesome side reactions. 

Sulfurane reagent lor conversion of trans diols to epoxides, generally for dehydration of diols to olefins or cyclic ethers, and as an oxidizing agent... 

TiPSON - COHEN Oleflnatlon Conversion o( sugar glycols via epoxides into sugar olefins. 

The oxidation of alkenes and allylic alcohols with the urea-EL202 adduct (UELP) as oxidant and methyltrioxorhenium (MTO) dissolved in [EMIM][BF4] as catalyst was described by Abu-Omar et al. [61]. Both MTO and UHP dissolved completely in the ionic liquid. Conversions were found to depend on the reactivity of the olefin and the solubility of the olefinic substrate in the reactive layer. In general, the reaction rates of the epoxidation reaction were found to be comparable to those obtained in classical solvents. 

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