Ethyl maleate

Let us suppose it is desired to calculate the theoretical yield of ethyl maleate when 33 g. of silver maleate, suspended m dry ether, are treated with the calculated quantity of ethyl iodide (31-2 g.). 

From the equation representing the chemical reaction involved, it is evident that 330 g. of silver maleate will theoretically react with 312 g. of ethyl iodide in ethereal solution to produce 172 g. of ethyl maleate. It follows, therefore, that 33 g. (0 1 mol) of silver maleate will react with 31-2 g. (0 2 mol) of ethyl iodide to give a theoretical yield of 17 2 g. (0-1 mol) of ethyl maleate. In practice, the actual yield found for these quantities is of the order of 16 0 g. the percentage yield is therefore (16 0/17-2) X 100 = 93 per cent. 

Ethyl maleate of almost equal purity may be obtained by refluxing a mixture of 20 g. of pure maleic a.oid, 37 g. (47 ml.) of absolute ethyl alcohol, 05 ml. of sodium-dried benzene and 4 ml. of concentrated sulphuric acid for 12 hours. The ester is isolated as described for Diethyl Adipate (Section 111,100). The yield of diethyl maleate, b.p. 219-220°, is 26 g. 

The possibility of recycling the catalyst was also studied. In order to decrease the amount of ethyl maleate and fumarate, the addition rate of ethyl diazoacetate was reduced and the reaction temperature was kept low during the addition. Furthermore, the catalyst concentration was reduced by doubling the volume of ionic liquid. Under these conditions the catalyst was reused seven times, although both the yield and the enantioselectivity decrease from the fourth reuse on (entry 6 in Table 6). 

Ethyl fumarate has been prepared from fumaric acid and ethyl alcohol, with or without sulfuric acid as catalyst,4 from silver fumarate and ethyl iodide,5 from silver maleate and ethyl iodide plus a trace of iodine,6 from ethyl maleate by the action of iodine,6 from ethyl maleate and phosphorus pentachloride,7 and by passing hydrogen chloride into a boiling absolute alcohol solution of malic acid.8... 

Following are the percentage yields obtained in the preparation of other esters ethyl maleate, 73 ethyl salicylate, 70 ethyl oxalate, 80 ethyl benzoate, 92 methyl benzoate, 87. In the preparation of ethyl maleate troublesome emulsions were encountered in working up the product. Occasionally this hap-... 

Another example of the retention of volatile DA reagents is that of cyclopentadiene in a tandem retro-DA/DA prime reaction [15, 16, 38], This reaction type is the thermal decomposition of a DA adduct (A) and the generation of a diene (generally the initial diene) which is trapped in situ by a dienophile leading to a new adduct (B) [39]. Cyclopentadiene (22) (b.p. 42 °C) is generated by thermolysis of its dimer at approximately 160 °C [40]. An equimolar mixture of commercial crude dicyclopenta-diene (21) and dimethyl maleate was irradiated in accordance with the GS/MW process, in an open reactor, under 60 W incident power, for 4 min (8 x 30 s). The expected adduct 23 was isolated in 40% yield (Scheme 7.1). The isomeric composition of 23 (endo-endoIexo-exo = 65/35) was identical with that obtained under classical conditions from 22 and methyl maleate [41]. The overall yield of this tandem reaction can be increased from pure dimer 21 (61%) and the same tandem reaction has also been reported using ethyl maleate as dienophile [31]. 

Petrillo reported that the bis-acetoxymethylpyrrole 83 undergoes a sequential Diels-Alder reaction of the in situ generated 2,3-dimethylpyrrole with carbodienophiles (such as maleic anhydride, maleimide, ethyl maleate, fumaronitrile, and ethyl acrylate) to afford the octahydrocarbazoles 84 which can be oxidized with DDQ to the corresponding carbazole derivatives . 

Michael Faraday reported in 1821 that chlorine addition to alkenes is Stimulated by sunlightand today this is taken to indicate the involvement of a free radical process (equation 26). Free radical chain mechanisms were proposed in 1927 by Berthoud and Beraneck for the isomerization of stilbene catalyzed by Br2 (equation 27), and by Wachholtz for bromine addition to ethyl maleate (equation 28).Later studies showed inhibition of halogen addition by reaction of the intermediate radicals with oxygen, and a free radical chain mechanism for solution and gas phase halogenations as in equation (26) was shown (equation 29). Kinetic and mechanistic... 

A mixture of 228 g. (2.0 moles) of enanthaldehyde (Note 1) and 172 g. (1.0 mole) of ethyl maleate (Note 2) is placed in a jacketed flask (Fig. 3) (Note 3) with condensers attached to the flask and the jacket openings. The jacket is charged with trichloroethylene (Note 4), which is heated to reflux, and, when the reaction mixture reaches 84—85°, 0.5 g. of benzoyl peroxide is added to the mixture through the condenser. After 3-8 hours an additional 0.5-g. portion of benzoyl peroxide is added, and heating is continued for a total of 18-24 hours (Note 5). 

Ethyl maleate from Commercial Solvents Corporation, Terre Haute, Indiana, was distilled before use. Ethyl fumarate can be used also, but the yield of product is lower since a much greater proportion of high-boiling compounds is obtained. Aldehydes do not undergo free-radical addition to maleic anhydride under these conditions. 

Ethyl enanthylsuccinate has been prepared by the free-radical addition of enanthaldehyde to ethyl maleate.2... 

The formation of carbanions, according to Scheme 6, has been much studied but has proved to be of little preparative use. The benzyl anion, generated from benzyl-dimethylsulphonium tosylate, reacted with acrylonitrile but the addition product was formed in only low yield Similarly the reactive ylid formed by deprotonation of trimethylsulphonium salts has been cathodically generated and trapped by several aldehydes and ketones as well as ethyl maleate and fumarate examples are given in Scheme 7. For the best case (benzophenone), the epoxide was formed in 40%... 

Ethyl maleate of almost equal purity may be obtained by refluxing a mixture of... 

Ethyl cinnamate Ethyl maleate Ethyl oxalate... 

Ethylene bromide Ethyl ether Ethyl fumarate 2-Ethylhexanol Ethylidine diacetate Ethyl maleate Ethyl valerate Eugenol methyl ether... 

Now that fumaric and maleic acid are available commercially, the most convenient method of preparing the above ester consists in condensing ethyl malonate with ethyl fumarate1 or ethyl maleate.2 It has also been prepared by condensing malonic ester with ethyl chlorosuccinate 3 and with ethyl ethoxysucci-nate.4... 

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