Dicarboxylic acid esters

PolybenZimidaZoles. The polyben2imida2oles (PBIs) are generally produced by the high temperature, melt polycondensation reaction of aromatic bis-ortho-diamines and aromatic dicarboxylates (acids, esters, or amides) in a reaction such as that shown in equation 11 to form ben2imida2ole [51-17-2] as the repeating unit. 

The formation of porphyrins from 1,19-dideoxybi)enes-/r can be achieved starting either from the 1-methyl derivatives or from l,19-dideoxybilene-Z>-l,19-dicarboxylic acid esters. In the first case the desired methine bridge of the porphyrin stems from the 1-methyl group whereas in the latter case orthoformates have to be added in the condensation step as a precursor for the methine unit. The 1-methyl- and also 1,19-dimethyl-l,19-dideoxybilene- > salts can be cy-clized to the corresponding porphyrins with copper(II) acetate in methanol.56 However, when the bilenes contain /i-acceptor substituents, the yields of porphyrins obtained by this method are very low.57... 

The cyclization of 1,19-dideoxybilene-i-dicarboxylic acid esters has been widely used for the synthesis of porphyrins. In this case, the use of tert-butyl esters which can be hydrolyzed with trifluoroacetic acid prior to the cyclization step is necessary. The cyclization step also requires trifluoroacetic acid and orthoformates. However, attempts to prepare porphyrins with /f-acceptor substituents can give rise to problems with side products and yields. 

Russell and coworkers147 had found that treatment of dimsyl anion 88 or of a similar methylsulfonyl carbanion with 1,2-, 1,3- and 1,4-dicarboxylic acid esters can give five- to seven-membered cyclic compounds. By this type of cyclization, they prepared ninhydrin hydrate 106 from diethyl phthalate148,149. 

Toad bufadienolides occur not only by themselves but also in a conjugated form, sulfates, dicarboxylic esters and amino acid-dicarboxylic acid esters have all been reported (Steyn and van Heerden 1998). Because of the activity of the bufadienolides in inhibiting active monovalent cation transporters, it is suggested that these compounds have a role in maintaining sodium homeostasis in toads that migrate between fresh and salt water environments (Flier, I idwards, Daly and Myers 1980). 

Esters for lubricant applications are divided into five groups monocarboxylic acid esters (monoesters), dicarboxylic acid esters (diesters), glycerol esters, polyol esters, and complex esters. 

Dieckmann Condensation The intramolecular equivalent of a Claisen condensation where dicarboxylic acid ester undergoes base-catalyzed cyclization to form a P-keto ester. 

Polycondensation of diols with dicarboxylic acids is often performed in the melt. However, it does not always lead to high-molecular-weight polyesters. Sometimes, the starting materials or the resulting polyester are thermally unstable at the high condensation temperatures. If the reactants and the polyester are well soluble, one can carry out the polycondensation in solution (see Example 4-2). The elimination of water from diols and dicarboxylic acids frequently occurs rather slowly. In such cases suitable functional derivatives of the diols and dicarboxylic acids (esters or anhydrides) can be used instead of the direct condensation, as described in Sect. 4.1.1.3. 

Also brings down modulus and tensile strength and as a result, increases elongation which improves the low temperature characteristics. This may also lower Tg of the polymer or resin and thus facilitates their processing at a lower temperature. Some aliphatic dicarboxylic acid esters such as bis (2-ethyl hexyl) adipates, sebacates, azelates, etc. are most effective for this purpose. 

Another approach attempts to explain the different effect of the ester structure in different reaction media simply by the changing ability of the esters to be absorbed by the resin. Qualitatively, this approach was used [476] to interpret the results for water and aqueous acetone and a similar idea was suggested for the hydrolysis of dicarboxylic acid esters in water—dioxan mixtures [482,483]. Quantitative interpretation was based [481,489] on Helfferich s model [427]. It follows from eqn. (30) and from the relation... 

Polycondensation of diols with dicarboxylic acids or reesterification of dicarboxylic acid esters with diols are the main methods of preparing polyesters. Because of the reversibility of this classical polyester formation, high reaction temperatures, long polycondensation times and low pressures are required to remove low molecular weight reaction products in order to shift the equilibrium to the direction of polyester formation and to obtain sufficiently high molecular weights. 

Preparation and Solubility of Polyesters. A number of polyesters were prepared from several diols and dicarboxylic acid esters to determine the effect of structure on the solubility in typical solvents used in lacquers. The data in Table I show that solubility in the solvents decreased in the following order toluene > methyl ethyl ketone > butyl acetate. Polymers that were soluble in all three solvents are examples 9-14. 

As a first approach to the synthesis of nagilactone 296, a norditer-penoid isolated from Podocarpaceae, which inhibit the expansion and mitosis of plant cells, an intramolecular Diels-Alder reaction of allene 1,3-dicarboxylic acid esters was used. The cyclization of 297 afforded the 8-lactone 298, rather than the y-lactone 299 [85JCS(P1)747]. 

This reaction offers some advantages over conventional methods as many acyloins can only be prepared by this method in good yields. Thus, by using ethyl acetate (289) in the first step 2,3-bis-(trimethylsiloxy)-2-butene (290) is obtained which can be easily hydrolysed to acetoin (310)19. Dicarboxylic acid esters undergo an intra-... 

The main aroma compounds identified as specific botrytized odorants are indicated in Table 6.6. It seems that while the terpene content decreases, numerous hydroxy-, oxo-, and dicarboxylic acid esters, acetals, and lactones form, all typically in lower concentrations or absent in normal wines (Miklosy and Kerenyi, 2004 Miklosy et al., 2000, 2004 Schreier et al, 1976). 

The nature of the Botrytis aroma compounds has been subjected to extensive research. In addition to the older findings about the importance of hydroxy-, oxo-, and dicarboxylic acid esters, acetals, and some special y- and 8-lactones, the role of volatile thiols has recently been elucidated. Nonetheless, additional research is needed to identify odor active compounds that are specific for botrytized wines. 

Which isomer of (LXIII) is actually formed remains an open question. In addition to the expected cyclic and open-chain products, two isomeric dicarboxylic acid esters are produced. These result from the reaction of the allyl intermediate with a second molecule of acrylic ester, followed by... 

Jimenez-Rodriguez C, Eastham GR, Cole-Hamilton DJ (2005) Dicarboxylic acid esters from the carbonylation of unsaturated esters under mild conditions. Inorg Chem Commun 8(10) 878-881... 

Cyclizative condensations based on aldol-type reactions which conform to the IIbd pattern have also been developed. Condensation of bis(alkoxycarbonylmethyl)amines or bis(cyanomethyl)amines with benzil affords 3,4-diarylpyrrole-2,5-dicarboxylic acid esters or nitriles. These reactions frequently lead to partial hydrolysis of at least one of the alkoxycarbonyl substituents and if the 3,4-diarylpyrrole is the ultimate objective, work-up involving complete hydrolytic decarboxylation is appropriate (equation 119) (61LA(639)102, 65JOC859). 

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