Carboxylic acid esters benzoates

The photochemistry of carboxylic acid derivatives has been summarized by Coyle [20]. For arene carboxylic acid esters it has been shown that [2+2] cycloaddition competes with hydrogen abstraction by the excited ester from an allylic position of the alkene. The addition of methyl benzoate 17 to... 

Thiete structures have been suggested as fragmentation products in the mass spectra of a thietane fused to a 3-lactam, an ortho disulfide of a thiolbenzoate ester, -propanethiol, thiirane carboxylic acid esters, isothiazoles, thiazoles, 1,3-dithiole 2-thiones, 1,3-dithiolene-2-ones, S-ethyl thio-benzoate, and thianaphthene sulfones. Tetramethylthiete may have been formed on thermolysis of the p-toluenesulfonyl-hydrazone of 2,2,4,4-tetramethyl-3-thietanone. " Thiete 2-thione may be an intermediate in the decomposition of 1,2-ditholium salts by the action of bases. " 2,2-Diphenyl-2H-thiete is suggested as an intermediate in the reaction of diphenyldiazomethane with 1,2,3-benzo-thiadiazole which yields 9-phenylthioxanthene and three other products. ... 

If carboxylic acid esters are readily available, they provide a convenient basis for the preparation of acid halides. Modified phosphorus halides, like 2,2,2-trichloro-l,3,2-benzodioxaphosphole can be applied successfully. This reagent forms first a 1,1-dichloroalkyl ether, which decomposes to the acid chloride (equation 16). The reaction conditions are rather drastic. For instance -butyl benzoate has to be heated for 4 h at 180 °C in order to get a 90% yield of benzoyl chloride. The only stable and isolable 1,1-dichloro ether is a,a-dichloromethyl methyl ether, which, as described above, is used as a mild reagent for the conversion of carboxylic acids to their chlorides. Similarly severe conditions are required if the chlorine or bromine adduct of triphenylphosphine is selected. This reaction may be catalyzed by BF3. It has been applied successfully to unsaturated esters and to the cleavage of lactones. 

Reduction of carboxylic acid esters. Esters are not reduced by sodium borohydride. However, if ethanedithiol is added (excess), most benzoate esters are reduced to benzyl alcohols in high yield. Thiophenol and ethylmercaptan do not share this property. Several aliphatic esters are also reduced by NaBH4 activated by HSCHjCHjSH. ... 

The direct introduction of the two-carbon unit of the heterocyclic ring, ortho to an existing carboxylic acid (ester) can be achieved in two ways ort/io-bromobenzoates can be coupled with 7r-(2-methoxyallyl)nickel bromide for the introduction of acetonyl, or thallation of benzoic acids, ortho to the carboxyl, can be followed by palladium-catalysed coupling with alkenes. Benzoates carrying an ortho acetylenic substituent can be ring closed using mercuric acetate, as shown below." ... 

Sodium benzoate, organophosphate salts and phosphate esters, noibomene caiboxy-lic-acid salt, p-tallow toluenesulfonamide, carboxylic acid esters, carboxylic acid salts, talc, di-substituted benzaldehyde and l,3 2,4-bis(3 4 -dimethylbenzyhdene) sorbitol are good candidates for nucleation of ethylene-vinyl acetate copolymer used in interlayers of multiple layer glass panels." ... 

The essential point of these improved highly active supported catalyst system is that Lewis base such as ethyl benzoate(E.B.) is included to modify isotacticity. In spite that many Lewis bases such as ethers, esters, ketons and amines are known to increase the isotacticity of the polymer / (Table l), almost all researchers interest concerning Lewis bases had been focussed on organo carboxylic acid ester, particularly on aromatic carboxylic acid ester. 

Although most applications use smecto-gens of positive dielectric anisotropy, there are some wide temperature range smecto-gens of negative dielectric anisotropy. Some notable examples are the lateral cyano phenyl benzoates [18] (6) and the 2,3-difluoro-biphenyl carboxylic acid esters [19], e.g.. 

Besides acetates and benzoates many other types of carboxylic acid esters can be formed, such as chloroacetates, trifluoroacetates, pivalates, carbonates, and thiocarbonates, by reaction with chloroacetic anhydride, trifluoroacetic anhydride, pivaloyl chloride (2,2-dimethyl propanoyl chloride), phosgene or methylchloro-formate, and carbon disulfide or carbonyl sulfide, respectively. Each of the ester derivatives imparts specific chemical properties to the carbohydrates so they can be used selectively in synthetic schemes. It was found that the sulfonic acid esters... 

Coyle has summarized the photochemistry of carboxylic acid derivatives. For arene carboxylic acid esters it has been shown that [2-1-2]-cycloaddition competes with hydrogen abstraction by the excited ester from an allylic position of the alkene. The addition of methyl benzoate 17 to 2-methyl-2-butene gave a 1 1 mixture of the Paterno-Bilchi adduct 18 and the coupling product 19. Less electron-rich alkenes (e.g., cyclopentene) did add preferentially toward the benzene ring of 17 in an ortho- and metacycloaddition manner. Furans could also be added photochemically to methyl benzoate and other aren-ecarboxylic acid esters. The resulting bicyclic oxetanes could be transformed into a series of synthetically valuable products. [2-1-2]-Cycloadducts and/or their cleavage or rearrangement products have also been described for photoreactions of alkenes with diethyl oxalate,benzoic acid, " and carbamates. ... 

Some carboxylic acid esters undergo isotopic exchange as part of the mechanism of hydrolysis (Bender, 1951). Thus alkyl benzoates exchange... 

Carbanions derived from optically active sulfoxides react with esters, affording generally optically active )S-ketoesters ° . Kunieda and coworkers revealed that treatment of (-t-)-(R)-methyl p-tolyl sulfoxide 107 with n-butyllithium or dimethy-lamine afforded the corresponding carbanion, which upon further reaction with ethyl benzoate gave (-l-)-(R)-a-(p-tolylsulfinyl)acetophenone 108. They also found that the reaction between chiral esters of carboxylic acids (R COOR ) and a-lithio aryl methyl sulfoxides gave optically active 3-ketosulfoxides The stereoselectivity was found to be markedly influenced by the size of the R group of the esters and the optical purity reached to 70.3% when R was a t-butyl group. 

Ruthenium tetroxide is a potent oxidant, however, and it readily attacks carbon-carbon double bonds.19 Primary alcohols are oxidized to carboxylic acids, methyl ethers give methyl esters, and benzyl ethers are oxidized to benzoate esters. 

Hydrogenolyses of carboxylic acids and esters to the corresponding aldehydes seems very attractive due to their simplicity. Copper chromites are the most widely used catalysts.15 Raney copper and zinc oxide-chromium oxide have also been used for this process.16-18 The hydrogenolysis of methyl benzoate to benzaldehyde was studied on various metal oxides at 300-350°C. ZnO, Zr02 and Ce02 presented high activities and selectivities (Scheme 4.8). 

Studies of metallo-ester [Pd-COOPh] versus benzoate [Pd-OOCPh] indicate that only the former complex underwent decarboxylation with heating, suggesting that a metallo-carboxylic acid rather than formate mechanism likely operates for water-gas shift. 

Reactions of A-acyloxy-A-alkoxyamides (90) with A-methylaniline in methanol or aqueous acetonitrile afforded quantitative yields of esters (130), carboxylic acid (132) and half an equivalent of A,A -dimethyl-A,A -diphenyltetrazene (131) (equation 15). The reaction is promoted by polar solvents and ester formation was shown to involve an intramolecular process a crossover experiment using a mixture of A-acetoxy-iV-butoxy-4-toluamide (90, R = Bu, R = Me, R = 4-MeC6H4) and A-acetoxy-A-ethoxybenzamide (90, R = Et, R = Me, R = Ph) afforded clean yields of butyl 4-toluate (130, R = Bu, R = 4-McC6H4) and ethyl benzoate (130, R = Et, R = Ph)". ... 

Preparation 212.—Methyl Benzoate (Methyl ester of benzenemono-carboxylic acid). 

Esters, like carboxylic acids, are normally reduced with lithium aluminum hydride. In these reactions, two alcohols are formed. An example is the reduction of methyl benzoate to benzyl alcohol and methanol. 

Since ketene is probably the intermediate of the Wolff rearrangement, the choice of solvents dictates the nature of the product. Indeed, water gave carboxylic acids, whereas alcohols or amines led to esters and amides, respectively. These combinations have been applied to the synthesis of more complex molecules. For example, the total synthesis of carbonolide B, a 16-membered macrolide antibiotic, relied on Amdt-Eistert homologation. In this sequence, a protected furanuronic acid was transformed to the corresponding a-diazoketone, which was then converted to its homologous carboxylic ester. The reaction was achieved using catalytic amounts of silver benzoate and excess of triethylamine in methanol (Scheme 3.4).11... 

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