Carboxylic acids, unsaturated epoxidation

Isomerization has been observed with many a,j3-unsaturated carboxylic acids such as w-cinnamic 10), angelic, maleic, and itaconic acids (94). The possibility of catalyzing the interconversion of, for example, 2-ethyl-butadiene and 3-methylpenta-l,3-diene has not apparently been explored. The cobalt cyanide hydride will also catalyze the isomerization of epoxides to ketones (even terminal epoxides give ketones, not aldehydes) as well as their reduction to alcohols. Since the yield of ketone increases with pH, it was suggested that reduction involved reaction with the hydride [Co" (CN)jH] and isomerization reaction with [Co (CN)j] 103). A related reaction is the decomposition of 2-bromoethanol to acetaldehyde... 

Shibasaki et al. have reported a new approach to a,/3-epoxy esters the epoxidation of cv. j-unsaturated carboxylic acid imidazolides with a La(OPr )3, BINOL, Ph3As=0, and TBHP system provides epoxy-peroxy-esters (41), which are generated in situ from the intermediary epoxy acid imidazolide and converted to the corresponding methyl ester (42) upon treatment with methanol (Scheme 27).134... 

Molybdenum and tungsten compounds have long been known to catalyze the transformations of alkenes into epoxides and diols by hydrogen peroxide.171"173 This reaction was found to be suitable for the epoxidation of water-soluble alkenes such as allylic alcohols (equation 30)174,175 or unsaturated carboxylic acids (equation 31).171 Tungsten catalysts were found to be more active and selective in aqueous solution than molybdenum complexes. 

The above system could further be applied to the epoxidation of allylic alcohols [35, 36], monoterpenes [37] and oc,P-unsaturated carboxylic acids [38], the oxidation of alcohols [35, 36], amines [39] and alkynes [40], and the oxidative transformation of diols [35, 41-44]. The subsequent spedroscopic and kinetic studies by many researchers show that [P04 W0(02)2 4]3 is a true catalytically adive species formed by the readion of H3[PW12O40] with excess H202 (Figure 6.3) [45-48],... 

The conversion of an alkene to a halohydrin can also be considered as an epoxidation because this can be achieved by a simple ring closure.184 Although no reagent is yet available to perform an asymmetric conversion of an isolated alkene to a halohydrin, the reaction can be controlled through diastereoselection. One such case is the halolactonization of y,8-unsaturated carboxylic acids, N,N-dialkylamides.185189... 

Similar oxidants are used for epoxidation of esters of unsaturated carboxylic acids. Methyl oleate is oxidized with peroxybenzoic acid [295] or peroxylauric acid [174] to methyl 9,10-epoxystearate acid in respective yields of 67 and 76%. Alkaline 50% hydrogen peroxide in methanolic solution transforms diethyl ethylidenemalonate at pH 8.5-9.0 and at 35-40 C over a period of 1 h into ethyl 2-ethoxycarbonyl-2,3-epoxybutyrate in 82% yield [145], A somewhat exotic oxidizing agent, dimethyldioxirane, converts ethyl tra/u-cinnamate into ethyl 2,3-epoxyhydrocinnamate in 63% isolated yield [210]. 

Conjugation of the alkene double bond with an electron-withdrawing group reduces the rate of epoxidation. Thus, a, 3-unsaturated carboxylic acids and esters require a stronger oxidant, such as trifluoroperoxyacetic acid, for oxidation. 

Sturtz et al. have described the deprotonation of the allyl bis(dimethylamido)phosphonate (9). Treatment of (9) with two equivalents of base, followed by reaction with an epoxide and hydrolysis, yields the y-lactone (Scheme 10). Alkylation with alkyl and alkenyl halides occurs at the y-carbon and hydrolysis yields the saturated and unsaturated carboxylic acids respectively. 

Warwel, S. and Rusch-Klaa, M., Chemo-enzymatic epoxidation of unsaturated carboxylic acids, J. Molec. Catal. B, 1, 29-35, 1995. 

Warwel, S., and M. Riisch gen. Klaas, Chemo-Enzymatic Epoxidation of Unsaturated Carboxylic Acids./. Mol. Catal. B 1 29-35 (1995). 

Hydrogen peroxide can react with carboxylic acid to form peracid when lipase enzyme is used as a catalyst instead of inorganic acid. The peracid will epoxidize alkenes, which results in the regeneration of the carboxylic acid (Scheme 7). The best results were obtained in the nonpolar solvents toluene and hexane or when mixtures of alkene and carboxylic acid were used without solvent (55). Lipases were immobilized on cellulose, polysulfone membranes, or polypropylene beads (56). The lipases were used to convert caprylic acid to its peracid. The peracid was used to convert oleic acid to its epoxide. The best yield of epoxy stearic acid (81%) was obtained with the lipase from Candida antartica. Using a commercial preparation of immobilized C. antartica lipase, various unsaturated carboxylic acids were treated with... 

The epoxidation of a,P-unsaturated carboxylic acid is difficult. However, the epoxidation can be achieved with H O in presence of Na WO at pH 5.8-6.8 (Scheme 65). 

Alternatively the above epoxidation of a,p-unsaturated carboxylic acids can be achieved by using ozone-acetone system and buffering the reaction with NaHCOj in 75-80% yield. 

Radical substitution of the hydrogen from the methyl groups PHj OH,X Kl( -HY CH3 X CH, hc=ch X-Y = Br-Br,C1-C1 (12) RS0.-C1 (13) I 1 ( ) Halogenation, sulfonation, binding of maleric anhydride group, unsaturated carboxyl acids, amides, imides, esters, epoxides, amines, alcohol can be used Product of (12) is precursor for PCMs, that of (13) for direct PCMs. 

Numerous methods of modifying epoxidized polydienes aim at introducing into the structure of these resins some unsaturated groups with increased reactivity. One of these is the reaction of oxiranic groups with unsaturated carboxylic acids (acrylic, methacrylic, itaconic) [222] and, more frequently, with acrylic hydroxy esters, like 2-hydroxyethylmethacrylate, 2-hydroxyethylaciylate, and especially reaction products of the semiester type obtained by the reaction between hydroxyalkylmethacrylates and polycarboxylic acid anhydrides [223,224]. 

Group of plastics composed of resins produced by reactions of epoxides or oxiranes with compounds such as amines, phenols, alcohols, carboxylic acids, acid anhydrides and unsaturated compounds. 

Furthermore, an a,P-ethylenically unsaturated aldehyde together with organic amines will form intermediate products, which are further reacted with a carboxylic acid, an organic halide, or an epoxide-containing compound [ 1760]. The final products are suitable corrosion inhibitors for preventing corrosion of steel in contact with corrosive brine and oil and gas well fluids. 

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