By transesterification

Some esters of substituted alcohols have been synthesized by transesterification. Treatment of 4-methyl-5-thiazolecarboxylic acid (14) with 3-chloroethyldiethylamine in acetone in the presence of anhydrous potassium carbonate gives the desired ester (15) in good vield (60%) (Scheme 10) (163). 

Dialkylaminoethyl acryhc esters are readily prepared by transesterification of the corresponding dialkylaminoethanol (102,103). Catalysts include strong acids and tetraalkyl titanates for higher alkyl esters and titanates, sodium phenoxides, magnesium alkoxides, and dialkyitin oxides, as well as titanium and zirconium chelates, for the preparation of functional esters. Because of loss of catalyst activity during the reaction, incremental or continuous additions may be required to maintain an adequate reaction rate. 

Alternative technology for modifying a poly(aLkylene terephthalate) by incorporation of a phosphinate stmcture has been developed by Enichem. Phosphinate units of the stmcture —P(CgH5) (0)CH20— are introduced into a polyester such as PET or PBT by transesterification with an oligomer comprised of the aforementioned units (136). 

Cychc carbonates result from polyols by transesterification using organic carbonates (115). Thus sorbitol and diphenylcarbonate in the presence of dibutyl tin oxide at 140—150°C form sorbitol tricarbonate in quantitative yield (116). 

Linalool can be converted to geranyl acetone (63) by the CarroU reaction (34). By transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give the geranyl acetone. 

Higher aUphatic alcohol and phenoHc group-containing polytitanates may be prepared by transesterification of TYZOR BTP (24). 

Polyester Polyols. Initially polyester polyols were the preferred raw materials for polyurethanes, but in the 1990s the less expensive polyether polyols dominate the polyurethane market. Inexpensive aromatic polyester polyols have been introduced for rigid foam appHcations. These are obtained from residues of terephthaHc acid production or by transesterification of dimethyl terephthalate (DMT) or poly(ethylene terephthalate) (PET) scrap with glycols. 

Chemistry. Poly(vinyl acetate) can be converted to poly(vinyl alcohol) by transesterification, hydrolysis, or aminolysis. Industrially, the most important reaction is that of transesterification, where a small amount of acid or base is added in catalytic amounts to promote the ester exchange. 

Oils are mixtures of mixed esters with different fatty acids distributed among the ester molecules. Generally, identification of specific esters is not attempted instead the oils are characterized by analysis of the fatty acid composition (8,9). The principal methods have been gas—Hquid and high performance Hquid chromatographic separation of the methyl esters of the fatty acids obtained by transesterification of the oils. Mass spectrometry and nmr are used to identify the individual esters. It has been reported that the free fatty acids obtained by hydrolysis can be separated with equal accuracy by high performance Hquid chromatography (10). A review of the identification and deterrnination of the various mixed triglycerides is available (11). 

Amino alcohols can be resolved by a number of pathways including hydrolysis, esterification, and transesterification. For example, hydrolysis of Ai,0-diacet5l-2-amino-l-butanol with PPL followed by recrystallization results in (80a) with 95% ee (108). Hydrolysis of racemic acetates or butyrates of 2-[(aLkoxycarbonyl)amino]-l-aLkanols with PFL gives (R)-alcohol (81) with 95% ee (109). (3)-(81) can be obtained by transesterification of the racemic (81) with ethyl acetate which also serves as the reaction medium (109). 

Acrylic Esters. A procedure has been described for preparation of higher esters from methyl acrylate that illustrates the use of an acid catalyst together with the removal of one of the products by azeotropic distillation (112). Another procedure for the preparation of butyl acrylate, secondary alkyl acrylates, and hydroxyalkyl acrylates using -toluenesulfonic acid as a catalyst has been described (113). Alurninumisopropoxide catalyzes the reaction of amino alcohols with methyl acrylate and methyl methacrylate. A review of the synthesis of acryhc esters by transesterification is given in Reference 114 (see... 

J. K. Haken, Synthesis of Acrylic Esters by Transesterification Noyes Development Corp., Park Ridge, N.J., 1967. 

The Dim ester was developed for the protection of the carboxyl function during peptide synthesis. It is prepared by transesterification of amino acid methyl esters with 2-(hydroxymethyl)-l,3-dithiane and Al(/-PrO)3 (reflux, 4 h, 75°, 12 torr, 75% yield). It is removed by oxidation [H2O2, (NH4)2Mo04 pH 8, H2O, 60 min, 83% yield]. Since it must be removed by oxidation it is not compatible with.sulfur-containing amino acids such as cysteine and methionine. Its suitability for other, easily oxidized amino acids (e.g., tyrosine and tryptophan) must also be questioned. It is stable to CF3CO2H and HCl/ether. - ... 

Dibenzyl phosphoramidates have been prepared from amino acids and the j)hos-phoryl chloride, (Bn0)2P(0)Cl. ° A diphenyl phosphoramidate has been prepared from a glucosamine it is converted by transesterification into a dibenzyl derivative to facilitate cleavage. ... 

By transesterification of a methyl ester with t-BuOH and sulfated Si02- ... 

The cinnamyl ester can be prepared from an activated carboxylic acid derivative and cinnamyl alcohol or by transesterification with cinnamyl alcohol in the presence of the H-Beta Zeolite (toluene, reflux, 8 h, 59-96% yield). It is cleaved under nearly neutral conditions [Hg(OAc)2, MeOH, 23°, 2-A h KSCN, H2O, 23°, 12-16 h, 90% yield]or by treatment with Sulfated-Sn02, toluene, anisole, reflux. The latter conditions also cleave crotyl and prenyl esters. 

Ether, water, phenylboronic acid. Cleavage occurs by transesterification. 

Diphenyl phosphates are converted by transesterification to dibenzyl phosphates upon treatment with BnONa in THF at 25° in 83% yield. ... 

Polybutylene terephdialate (PBT) has been produced from PET scrap by transesterification widi 1,4-butanediol.1 In die process, classified and cleaned polymer Bake from postconsumer PET bottles is reacted witit 1,4-butanediol in an extruder. PBT is used as an engineering plastic. Ethylene glycol and tetrahydrol uran produced as by-products are recovered by distillation. 

Compared with the fatty alcohol sulfates, which are also oleochemically produced anionic surfactants, the ester sulfonates have the advantage that their raw materials are on a low and therefore cost-effective level of fat refinement. The ester sulfonates are produced directly from the fatty acid esters by sulfona-tion, whereas the fatty alcohols, which are the source materials of the fatty alcohol sulfates, have to be formed by the catalytic high-pressure hydrogenation of fatty acids esters [9]. The fatty acid esters are obtained directly from the fats and oils by transesterification of the triglycerides with alcohols [10]. 

For technical applications, the production of ester sulfonates from the (purified) sulfo fatty acids involves too much effort, especially because the relevant fatty acid esters can be produced directly from the triglycerides of fats and oils by transesterification. The only possible way to produce ester sulfonates is the sulfonation of fatty acid esters. 

The development of monoalkyl phosphate as a low skin irritating anionic surfactant is accented in a review with 30 references on monoalkyl phosphate salts, including surface-active properties, cutaneous effects, and applications to paste and liquid-type skin cleansers, and also phosphorylation reactions from the viewpoint of industrial production [26]. Amine salts of acrylate ester polymers, which are physiologically acceptable and useful as surfactants, are prepared by transesterification of alkyl acrylate polymers with 4-morpholinethanol or the alkanolamines and fatty alcohols or alkoxylated alkylphenols, and neutralizing with carboxylic or phosphoric acid. The polymer salt was used as an emulsifying agent for oils and waxes [70]. Preparation of pharmaceutical liposomes with surfactants derived from phosphoric acid is described in [279]. Lipid bilayer vesicles comprise an anionic or zwitterionic surfactant which when dispersed in H20 at a temperature above the phase transition temperature is in a micellar phase and a second lipid which is a single-chain fatty acid, fatty acid ester, or fatty alcohol which is in an emulsion phase, and cholesterol or a derivative. 

Amine salts of acrylate ester polymers, which are physiologically acceptable and useful as surfactants, are prepared by transesterification of alkyl acrylate polymers with 4-morpholinethanol or the alkanolamines and fatty alcohols or alkoxy-lated alkylphenols, and neutralizing with phosphoric acid. The product was used as an emulsifying agent for oils and waxes [60]. 

Ester alcoholysis (transesterification) in organic media is an equilibrium reaction and must be shifted in the desired direction. For example, Bornscheuer and coworkers [61] reported the resolution of ibuprofen vinyl ester by transesterification tvith n-hexanol in the presence of CAL-B. The vinyl alcohol generated during the reaction tautomerizes to acetaldehyde, thus making the reaction irreversible, as illustrated in Figure 6.14. 

The enzymatic resolution of esters via aminolysis or ammonolysis processes represents an efficient alternative to the resolution of substrates by transesterification... 

FIGURE 5 Stepwise synthesis of a triblock copolymer (PCL-PLA-PCL) of PCL and polylactic acid using aluminum coordination catalysts to minimize randomization of the block structure by transesterification. (From Ref. 43.)... 

Synthesis of dimethyl carbonate by transesterification of ethylene carbonate and methanol using quaternary ammonium salt catalysts... 

Yun-Jin Fang and Wen-De Xiao, Experimental and modeling studies on a homogeneous reactive distillation system for dimethyl carbonate synthesis by transesterification, Separation and purification technology, 34 (2004) 255. 

Cyclic carbonate esters are easily prepared from 1,2- and 1,3-diols. These are commonly prepared by reaction with A.A -carbonyldiimidazole214 or by transesterification with diethyl carbonate. 

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