Esters reaction with base

IsoxazoIidine-3,3-dicarboxylic acid, 2-methoxy-dimethyl ester reaction with bases, 6, 47 Isoxazolidine-3,5-diones synthesis, 6, 112, 113 Isoxazoli dines conformation, 6, 10 3,5-disubstituted synthesis, 6, 109 oxidation, 6, 45-46 PE spectra, 6, 5 photolysis, 6, 46 pyrolysis, 6, 46 reactions, 6, 45-47 with acetone, 6, 47 with bases, 6, 47 reduction, 6, 45 ring fission, S, 80 spectroscopy, 6, 6 synthesis, 6, 3, 108-112 thermochemistry, 6, 10 Isoxazolidin-3-ol synthesis, 6, 111 Isoxazolidin-5-oI synthesis, 6, 111... 

The mechanism involves the formation of anion 3 from ester 1 by reaction with base ... 

From oxiho-Hydroxyaraldehydes and Bis(methylthio)methylidene-Ketones In a route which certainly involves formation of the ester linkage as a hrst step, ortfto-hydroxy-araldehydes react with bis(methylthio)methylidene-ketones (easily generated from methyl ketones by reaction with base, then carbon disulfide, then iodomethane), the ring closure taking place without further intervention. ... 

Occasionally both isomers of a compound are needed and then stereoselective reactions with a poor degree of selectivity are an advantage Both cis (35) and trans (36) tosylates were needed to study their reactions with base. The tosylates can obviously be made from the alcohols (37) by chemoselective (Chapter 5) tosylation of the less hindered primary OH groups, and reduction of the readily available (Chapter 19) keto ester (38) is a suitable weakly stereoselective route to (37). 

The Claisen condensation mechanism involves reaction of one ester molecule with base to form an enolate, which reacts as a nucleophile with another molecule of ester to give a carbonyl addition intermediate, in which the —OR group is lost to give a S-ketoester, which is deprotonated at the a position by the RO . 

Hydroxide ions open the lactone ring of coumarin forming the dianion 6 of (Z)-(2-hydroxy)cinnamic acid (coumarinic acid), which recyclizes to coumarin on addition of acid. On methylation with dimethyl sulfate, the dianion 6 is transformed to the (Z)-methoxy ester 8 however, on prolonged reaction with base it isomerizes to the ( )-dianion 7 ... 

Alkynes undergo stoichiometric oxidative reactions with Pd(II). A useful reaction is oxidative carboiiyiation. Two types of the oxidative carbonyla-tion of alkynes are known. The first is a synthesis of the alkynic carbox-ylates 524 by oxidative carbonylation of terminal alkynes using PdCN and CuCh in the presence of a base[469], Dropwise addition of alkynes is recommended as a preparative-scale procedure of this reation in order to minimize the oxidative dimerization of alkynes as a competitive reaction[470]. Also efficient carbonylation of terminal alkynes using PdCU, CuCI and LiCi under CO-O2 (1 I) was reported[471]. The reaction has been applied to the synthesis of the carbapenem intermediate 525[472], The steroidal acetylenic ester 526 formed by this reaction undergoes the hydroarylalion of the triple bond (see Chapter 4, Section 1) with aryl iodide and formic acid to give the lactone 527(473],... 

Even though ketones have the potential to react with themselves by aldol addition recall that the position of equilibrium for such reactions lies to the side of the starting materials (Section 18 9) On the other hand acylation of ketone enolates gives products (p keto esters or p diketones) that are converted to stabilized anions under the reaction conditions Consequently ketone acylation is observed to the exclusion of aldol addition when ketones are treated with base m the presence of esters... 

The amide group is readily hydrolyzed to acrylic acid, and this reaction is kinetically faster in base than in acid solutions (5,32,33). However, hydrolysis of N-alkyl derivatives proceeds at slower rates. The presence of an electron-with-drawing group on nitrogen not only facilitates hydrolysis but also affects the polymerization behavior of these derivatives (34,35). With concentrated sulfuric acid, acrylamide forms acrylamide sulfate salt, the intermediate of the former sulfuric acid process for producing acrylamide commercially. Further reaction of the salt with alcohols produces acrylate esters (5). In strongly alkaline anhydrous solutions a potassium salt can be formed by reaction with potassium / /-butoxide in tert-huty alcohol at room temperature (36). 

Direct, acid catalyzed esterification of acryhc acid is the main route for the manufacture of higher alkyl esters. The most important higher alkyl acrylate is 2-ethyIhexyi acrylate prepared from the available 0x0 alcohol 2-ethyl-1-hexanol (see Alcohols, higher aliphatic). The most common catalysts are sulfuric or toluenesulfonic acid and sulfonic acid functional cation-exchange resins. Solvents are used as entraining agents for the removal of water of reaction. The product is washed with base to remove unreacted acryhc acid and catalyst and then purified by distillation. The esters are obtained in 80—90% yield and in exceUent purity. 

Alternatively, weak acids and certain salts have been found to extend the lifetimes of inherently rapid reactions which occur with highly reactive esters, such as bis(2,4-dinitrophenyl) oxalate (95). A chemiluminescent demonstration based on the oxaUc ester reaction has been described (96) and the reaction has been developed iato a practical lighting system. 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

Succinic esters condense with aldehydes and ketones in the presence of bases, eg, sodium alkoxide or piperidine, to form monoesters of alkybdenesuccinic acids, eg, condensation of diethyl succinate with acetone yields ethyl 2-isopropyhdenesuccinate (eq. 3). This reaction, known as Stobbe condensation, is specific for succinic esters and substituted succinic esters (98,99). 

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