Unsaturated carboxylic esters epoxidation

Lithiophosphide reagents have also found application in the synthesis of a range of chiral phosphines based on carbohydrate systems, e.g., (43), the key step being nucleophilic ring-opening of epoxide derivatives with lithium diphenyl-phosphide. A lithiophosphide-tosylate route has been used in the synthesis of the carbohydrate-based diphosphine (44). Conjugate addition of lithium diphenyl-phosphide to a,P-unsaturated carboxylic esters is the key step in the synthesis of... 

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... 

The tendency for PVC to degrade by the unzipping type of dehydrochlorination is reduced by the presence of heat stabilizers, such as barium and cadmium salts of high-molecular-weight carboxylic acids and epoxidized unsaturated aliphatic esters. The general reaction for cadmium salts is as follows ... 

Several characteristic recent examples describing the epoxidation of a,/ -unsaturated ketones (equations 26-28) and that of a,/TunsaUirated carboxylic esters (equations 29 and 30) are given below. 

Metallated 1-ethoxy-1,3-dienes 697 and 712, obtained from the corresponding acetals by means of the LICKOR base, have been treated with alkyl halides, epoxides, carbonyl compounds, carbon dioxide and carboxylic esters affording ( )-l-substituted 1-ethoxy-1,3-dienes and, after hydrolysis, a,P-unsaturated carbonyl compounds1007-1010 (Scheme 186). Intermediates 697 and 712 have been transformed into the corresponding vinyl stan-nanes, which were submitted to Stille couplings with iodobenzene and benzoyl chloride823. 

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. 

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]. 

Esters. The monoisobutyrate ester of 2,2,4-trimethyl- 1,3-pentanediol is prepared from isobutyraldehyde in a Tishchenko reaction (58,59). Diesters, such as trimethylpentane dipelargonate (2,2,4-trimethylpentane 1,3-dinonanoate), are prepared by the reaction of 2 mol of the monocarboxylic acid with 1 mol of the glycol at 150—200°C (60,61). The lower aliphatic carboxylic acid diesters of trimethylpentanediol undergo pyrolysis to the corresponding ester of 2,2,4-trimethyl-3-penten- l-ol (62). These unsaturated esters reportedly can be epoxidized by peroxyacetic acid (63). 

To overcome these drawbacks, in recent years much attention has been paid to the development of resins which cem be f2d ricated with the same processes as those for conventional polyester resins, but having superior properties. Vinyl ester resins are the result of such development efforts (4-6). Vinyl ester resins are addition products of Vcurious epoxide resins and ethylenically unsaturated mono-carboxylic acids ( ). It condsines the excellent mechcuiical, chemical cuid solvent resistemce of epoxy resins with the properties found in the unsaturated polyester resins. In general, the cured vinyl ester resin has physical properties superior to the cured conventional ester resin, particulcurly corrosion resistcuice. This arises from the differences in the number and arremgement of polar groups such as ester and hydroxyl groups eind ccurbon-to-ccirbon double bonds present in the polymer chains. 

Although Smh is more chemoselective than traditional dissolving metal reagents, it does react with sulfoxides, epoxides, the conjugated double bonds of unsaturated ketones, aldehydes and esters, alkyl bromides, iodides and p-toluenesulfonates. It does not, however, reduce carboxylic acids, esters, phosphine oxides or alkyl chlorides. In common with most dissolving metal systems, ketones with an a-hetero substituent suffer loss of the substituent rather than reduction of the carbonyl group. ... 

In the case of a sterically hindered allylic methoxycarbonyl group, the epoxida-tion of substituted cyclohexenes-1,4-dienes occurs on the opposite side. Further studies on the epoxidation of j3,7-unsaturated cyclohexenecarboxylic acids and esters indicate that the steric and polar effects of the COaMe group result mainly in anh -epoxidation while the carboxyl group in inert solvent exerts a syn directing effect. ... 

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