Fumaric acid, esterification

Isomerization is faciUtated by esterification at temperatures above 200°C or by using catalysts, such as piperidine and morpholine (6), that are effective in raising isomerization of fumarate to 95% completion. Resins made by using fumaric acid are exclusively fumarate polymers, demonstrate higher reactivity rates with styrene, and lead to a complete cross-linking reaction. 

Examples of polyfunctional carboxylic acids esterified by this method are shown in Table I. Yields are uniformly high, with the exception of those cases (maleic and fumaric acids) where some of the product appears to be lost during work-up as a result of water solubility. Even with carboxylic acids containing a second functional group (e.g., amide, nitrile) which can readily react with the oxonium salt, the more nucleophilic carboxylate anion is preferentially alkylated. The examples described in detail above illustrate the esterification of an acid containing a labile acetoxy group, which would not survive other procedures such as the traditional Fischer esterification. 

The checkers prepared diethyl fumarate by the sulfuric acid-catalyzed esterification of fumaric acid.7 Diethyl fumarate obtained from Aldrich Chemical Company, Inc., contained dimethyl fumarate as a contaminant. 

The mechanism of high-temperature, base-catalyzed esterification involves cyclic anhydride formation by the polycarboxylic acid, followed by base-catalyzed reaction of anhydride groups with cellulosic hydroxyls. Fumaric acid, which cannot form a cyclic anhydride because of the trans arrangement of the two carboxyl groups, fails to react with cotton in the presence of weak bases and heat. 

Unlike lactic acid, mandelic acid (7) occurs in nature only in small amounts and is therefore more expensive. Formerly, it was obtained by resolution of the racemate with a chiral base, such as l-phenylethylamines or ephedrine6, but enantioselective reductions of a-oxo-a-phenylacetic acid by chemical or biochemical methods have become feasible (Section D.2.3.I.). Esters of mandelic acid, e.g.. 8. can be prepared by any convenient esterification technique (see. for example, refs 7 and 46) and have been used for enantioselective protonation reactions (Sections C. and D.2.I.). Similar to the corresponding lactic esters, fumaric acid derivatives 9 are obtained from the mandelic esters and used as chiral dienophiles in diastereoselective Diels Alder reactions (Section D. 1.6.1.1.1.2.2.1.). 

Bafilomycin Al can be modified to bafilomycin C-1 by esterification with a fumaryl group at the hydroxyl moiety in the hemiacetal ring (Figure 6.30). For the incorporation of the fumaryl moiety, it was assumed that fumaric acid is first... 

During esterification, maleic acid readily isomerizes, when reacting with ethylene glycol, into the ira 5-isomer (fumaric add), with a conversion of about 95%. Hence in this instance, there would be no advantage using fumaric acid in place of maleic anhydride, unless 100% of the ira 5-configuration is required for some specific purpose. 

A second class of monomers was prepared in which carboxylate functional groups had a well-defined stereochemical relationship to each other and hence to the polymer repeat unit produced on ROMP. These were the set of endo,endo-, exo,exo- and endo,exo-5,6-dimethylcarboxylates of norbomene obtained via the Diels-Alder reactions of the dimethylesters of maleic and fumaric acids with cyclopentadiene and via addition of maleic anhydride followed by esterification this set of monomers leads to polymers in which the functional groups are close to the polymer backbone. 

Fumaric acid s carbon-carbon double bond and its two carboxylic acid groups make it suitable for many potential industrial applications (Table 11.1). It can act as starting material for polymerization and esterification reactions. 

Other olefin derivatives which form analogous complexes with Fe2(CO)9 include maleic anhydride, maleic and fumaric acids and their esters, acrolein, and cinnamaldehyde 111). Several of these complexes have also been obtained upon irradiation of the olefinic compounds with Fe(CO)5 112). Normal reactions of the functional groups of the ligand, e.g., esterification and hydrolysis, can be accomplished. Degradation of the maleic anhydride complex with HBr produces succinic add 112). 

Esterification. Both mono- and dialkyl maleates and fumarates are obtained on treatment of maleic anhydride or its isomeric acids with alcohols or alkoxides (25). An extensive review is available (59). Alkyl fumarates (18) often are made from isomeri2ation of the corresponding maleate (19) (60). 

Neises, B. and W. Steglich, Esterification ofcarboxyic acids with dicyclohexylcarbodiimide/4-dimethylaminopyridine tert-butyl ethyl fumarate. Organic Syntheses, 1990.7 p. 93-94. 

Equations (2.13) and (2.14) (Table 2.4) describe the synthesis of UP oligomers. This is usually carried out in bulk at elevated temperatures. During a first step, the temperature is kept in the range of 60-130°C and is increased up to 160-220°C in a second step. During this second step most of the maleate groups (cis isomer) are isomerized into fumarate groups (trans isomer), Eq. (2.15) (Table 2.4). The degree of isomerization is determined by the esterification conditions (temperature, acid content, catalyst, nature of the diol). It must be carefully controlled because the content of fumarate units determines many properties of UP networks. 

ESTERIFICATION OF CARBOXYLIC ACIDS WITH DICYCL0HEXYLCARB0DIIMIDE/4-DlfCTHYLAMINOPYRIDINE tert-BUTYL ETHYL FUMARATE... 

Mares et al. [52] recently concluded that hydrogen-ion catalysis during this esterification was not likely and that catalysis by undissociated acid occurred together with a reaction in which, kinetically at least, no form of catalysis was involved. On the other hand, Vansco-Szmercsanyi et al. [53] concluded that polyesterification of maleic, fumaric and succinic acids with ethylene glycol or 1,2-propylene glycol was catalysed by protons. Much work clearly remains to be done on defining the detailed mechanism of catalysis by the acidic species during esterifications. 

Unsaturated poly(ester-imide) resins are known having imide structures at the end of the molecule or in the backbone. Chain termination by imide is frequently done with the tetrahydrophthalic anhydride (23) aminoethanol (9) reaction product [10,201-204]. In the synthesis of these resins, maleic anhydride is used. It is cheap and a world-wide available raw material, having the advantage of generating per mol only one mol of distillate. Patents are known where fumar-ic acid is claimed, e.g., in [205], but it is probably not frequently used in industrial processes. Anyway, under the conditions of the esterification reaction, a part of the maleate is isomerised into the fumarate [206]. To get materials with good heat resistance the use of THEIC is claimed for branching the unsaturated poly(ester-imide) resins [202]. Flexibility and heat resistance are improved when fatty acids, e.g., castor oil fatty acid [205,207], are build into the macromolecule. 

ESTERIFICATION OF CARBOXYLIC ACIDS WITH DICYCLOHEXYL-CARBOOIINIDE/4-DINETHYLAMINOPYRIDINE tert-BUTYL ETHYL FUMARATE ((E)-2-Butened1o1c acid, etiqrl I,l-d1aethy1ethy1 ester)... 

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