Catalysis esters synthesis

The second step, nucleophilic attack of an alcohol or phenol on the activated carboxylic acid RCOIm (carboxylic acid imidazolide), is usually slow (several hours), but it can be accelerated by heating[7] or by adding a base[8] [9] such as NaH, NaNH2, imidazole sodium (ImNa), NaOR, triethylamine, diazabicyclononene (DBN), diazabicycloimdecene (DBU), or /7-dimethylaminopyridine to the reaction mixture (see Tables 3—1 and 3—2). This causes the alcohol to become more nucleophilic. Sodium alcoholate applied in catalytic amounts accelerates the ester synthesis to such an extent that even at room temperature esterification is complete after a short time, usually within a few minutes.[7H9] This catalysis is a result of the fact that alcoholate reacts with the imidazolide very rapidly, forming the ester and imidazole sodium. 

This section describes the synthesis of oxazolidine esters used as polymer hardeners that cannot be synthesized using chemical catalysis, the synthesis of polyurethane polymers with methods that avoid the use of isocyanates and the enzymatic synthesis of polyesters with low molecular weight dispersity. 

Under almost anhydrous conditions in organic medium, lipases can be used in the reverse mode for direct ester synthesis from carboxylic acids and alcohols, as well as transesterifications (acyl transfer reactions) which can be divided into alcoholysis (ester and alcohol), acidolysis (ester and acid), and interesterification (ester-ester interchange). The direct esterification and alcoholysis in particular have been most frequently used in asymmetric transformations involving lipases. The parameters that influence enzymatic catalysis in organic solvents have been intensively studied and discussed. ... 

Okahata, Y. and Ijiro, K., Preparation of a lipid-coated hpase and catalysis of glyceride ester synthesis in homogeneous organic solvents. Bull. Chem. Soc. Jpn., 65, 2411-2420, 1992. 

Cyanate esters (CEs) are formed in excellent yields by the reaction of the corresponding phenols with cyanogen halide [34]. The reaction scheme is shown in Scheme la. The reaction is usually carried out in solution, in the presence of a tertiary amine as the acid scavenger at very low temperatures. Since the trimer-ization reactions of cyanate esters are highly prone to catalysis by spurious impurities, the most difficult aspect of cyanate ester synthesis is their scrupulous purification. Low molar mass esters are purified by distillation or recrystallization. Polymeric cyanates are purified by repeated precipitation in non-solvents such as water, isopropanol, etc. While distillation and recrystallization lead to pure materials, the precipitation method for polymeric cyanates is not always conducive to obtaining pure materials. A recent patent application claims a purification method for polymeric cyanates based on treatment with cation and anion exchangers [35]. 

Dicarbonyl compounds can be made to cyclize with esters of 3-thiapentanedioic acid 21 under base catalysis (Hinsberg synthesis). This widely applicable and high-yield synthesis leads to substituted thiophene dicarboxylic esters 22 via a double aldol condensation, with the two CH2 groups of 21. Hydrolysis and decarboxylation of the esters yield 3,4-disubstituted thiophenes 23 [23] ... 

Amino-5-nitrosopyrimidines 2 cyclocondense with systems possessing an activated CH2 group (aldehydes, ketones, nitriles, esters, reactive methylene compounds, phenacylpyridinium salts) providing pteridines 3 on base catalysis Timmis synthesis) ... 

Ma F, Hanna MA (1999) Biodiesel production a review. Biores Technol 70 1-15 Magnusson A, Hull K, Holmquists M (2001) Creation of an enantioselective hydrolase by engineered substrate-assisted catalysis. J Am Chem Soc 123 4354 355 Manjon A, Iborra JL, Arocas A (1991) Short-chain flavour ester synthesis by immobilized lipase in organic media. Biotechnol Lett 13 339-345 Margolin A (1996) Novel crystalline catalysts. TIBTECH 14 223-230... 

The pH dependence of these systems is complex and not fully understood, however. For instance, the same lipase that when used for hydrolysis showed a typical sigmoidal pH -activity profile exhibited practically no pH dependence when used for catalysis of ester synthesis [66]. Evidently, in the very water poor medium of the esterification, the enzyme does not experience a changed environment. 

Abdulmalek, E Sauoi, HSM Tejo, BA Basri, M Salleh, AB Rahman, RNZA Rahman, MBA. Improved enzymatie galaetoseoleate ester synthesis in ionie liquids. Journal of Molecular Catalysis B Enzymatic, 2012, V. 76,37-43. 

Hernandez, F. J., A. P. de los Rfos, D. Gomez, M. Rubio, and G. Vfllora. 2006. A New Recirculating Enzymatic Membrane Reactor for Ester Synthesis in Ionic Liquid/ Supercritical Carbon Dioxide Biphasic Systems. Applied Catalysis B Environmental Cl (1-2) 121-126. 

Lozano, P., T. de Diego, D. Carrie, M. Vaultier, and J. L. Iborra. 2003a. Enzymatic Ester Synthesis in Ionic Liquids. Journal of Molecular Catalysis B Enzymatic 21 (l-2) 9-13. 

Tsitsimpikou, C., H. Daflos, and F. N. Kolisis. 1997. Comparative Studies on the Sugar Esters Synthesis Catalysed by Candida Antarctica and Candida Rugosa Lipases in Hexane. Journal of Molecular Catalysis B Enzymatic 3 (1-4) 189-192. 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

Contents Introduction and Principles. - The Reaction of Dichlorocarbene With Olefins. - Reactions of Dichlorocarbene With Non-Olefinic Substrates. -Dibromocarbene and Other Carbenes. - Synthesis of Ethers. - Synthesis of Esters. - Reactions of Cyanide Ion. - Reactions of Superoxide Ions. - Reactions of Other Nucleophiles. - Alkylation Reactions. - Oxidation Reactions. - Reduction Techniques. - Preparation and Reactions of Sulfur Containing Substrates. -Ylids. - Altered Reactivity. - Addendum Recent Developments in Phase Transfer Catalysis. 

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