Diethyl maleate, formation

The intriguing aspect of Dharwadkar and Hussain s study is the fact that they observed a second-order rate dependence on the concentration of the half-ester. Since the reaction is an esterification process, it would have been expected to give a first-order dependence on both the reactants. No explanation was forwarded by these authors for the discrepancy. Merca et have recently reported the kinetics of diethyl maleate formation from the half-ester and ethanol to be second order overall. Activation parameters are also given. 

The common by-products obtained in the transition-metal catalyzed reactions are the formal carbene dimers, diethyl maleate and diethyl fumarate. In accordance with the assumption that they owe their formation to the competition of olefin and excess diazo ester for an intermediate metal carbene, they can be widely suppressed by keeping the actual concentration of diazo compound as low as possible. Usually, one attempts to verify this condition by slow addition of the diazo compound to an excess (usually five- to tenfold) of olefin. This means that the addition rate will be crucial for the yields of cyclopropanes and carbene dimers. For example, Rh6(CO)16-catalyzed cyclopropanation of -butyl vinyl ether with ethyl diazoacetate proceeds in 69% yield when EDA is added during 30 minutes, but it increases to 87 % for a 6 h period. For styrene, the same differences were observed 65). 

The EfZ ratio of stilbenes obtained in the Rh2(OAc)4-catalyzed reaction was independent of catalyst concentration in the range given in Table 22 357). This fact differs from the copper-catalyzed decomposition of ethyl diazoacetate, where the ratio diethyl fumarate diethyl maleate was found to depend on the concentration of the catalyst, requiring two competing mechanistic pathways to be taken into account 365), The preference for the Z-stilbene upon C ClO -or rhodium-catalyzed decomposition of aryldiazomethanes may be explained by the mechanism given in Scheme 39. Nucleophilic attack of the diazoalkane at the presumed metal carbene leads to two epimeric diazonium intermediates 385, the sterically less encumbered of which yields the Z-stilbene after C/C rotation 357,358). Thus, steric effects, favoring 385a over 385 b, ultimately cause the preferred formation of the thermodynamically less stable cis-stilbene. 

A somewhat unusual copper catalyst, namely a zeolite in which at least 25% of its rhodium ions had been exchanged by Cu(II), was active in decomposition of ethyl diazoacetate at room temperature 372). In the absence of appropriate reaction partners, diethyl maleate and diethyl fumarate were the major products. The selectivity was a function of the zeolite activation temperature, but the maleate prevailed in all cases. Contrary to the copper salt-catalyzed carbene dimer formation 365), the maleate fumarate ratio was found to be relatively constant at various catalyst concentrations. When Cu(II) was reduced to Cu(I), an improved catalytic activity was observed. 

CsF induces the ring-opening cyclization of the thus obtained l-[2-(trimethylsilylmethyl)cyclopropylcarbonyl] imidazole 154 with diethyl fumar-ate or diethyl maleate to give the cyclobutanone 155 [80], The facile ring fission of 154 also occurs in the presence of BF3OEt with the formation of the corresponding y,<5-unsaturated carboxylic acid. (Scheme 55)... 

Matsumura and Bousch (1966) isolated carboxy lest erase (s) enzymes from the soil fungus Trichoderma viride und a bacterium Pseudomonas sp., obtained from Ohio soil samples, that were capable of degrading malathion. Compounds identified included diethyl maleate, desmethyl malathion, carboxylesterase products, other hydrolysis products, and unidentified metabolites. The authors found that these microbial populations did not have the capability to oxidize malathion due to the absence of malaoxon. However, the major degradative pathway appeared to be desmethylation and the formation of carboxylic acid derivatives. 

Terpolymers made from two different olefins and CO are known. They were first described in Brubaker s initial patent and involved the free radical initiated terpolymerization of CO and C2H with another olefin such as propylene, isobutylene, butadiene, vinyl acetate, diethyl maleate or tetrafluoroethylene More recently, in another patent, Hammer has described the free radical initiated terpolymerization of CO and C2H with vinyl esters, vinyl ethers or methyl methacrylate 26Reaction temperatures of 180-200 °C and a combined pressure of 186 MPa were employed. Typically a CO QH4 olefin molar ratio of 10 65 25 was observed in the terpolymers. In other patents, Hammer 27,28) has described the formation of copolymers with pendant epoxy groups by the free radical initiated polymerization of CO, QH4, vinyl acetate and glycidyl methacrylate. Reaction conditions similar to those stated above were employed, and a typical CO C2H vinyl acetate glycidyl methacrylate molar ratio of 10 65 20 5 was observed in the product polymer. 

The reaction of Ru(TMP) with ethyl diazoacetate yielded a carbene complex, e.g. Ru(CHC02Et)(TMP) [316], An excess of the diazo compound led to catalytic formation of cis- and trans diethyl maleate in an unexpected ratio of 15 1. The nucleophilic ethyl diazoacetate is proposed to attack the electrophilic carbene complex and produce an intermediate betaine-line species which eliminates both Ru(TMP) and N2 to form the maleates. Similar reactions were observed with Os(TTP) complexes [313a], These reactions are reminiscent of the above-mentioned lability of a putative methyleneruthenium porphyrin. 

Mixed coupling of two dissimilar activated olefins A and B is best rationalized by path 3). To suppress the formation of symmetric dimers AA and BB besides the wanted mixed dimer AB the difference in reduction potential between A and B should be 0,2 to 0,4 V. Cpe at the potential of the more easily reducible olefin A with an excess of B present in the electrolyte yields predominantly AB. With equal amounts of A and B AA and AB are obtained and with small differences in the reduction potentials of A and B all three possible dimers are formed. Thus coreduction of diethyl maleate (Ei/2 = -1,32 V.) and acrylonitrile (E j. 2 = -1,94 V.) by cpe at -1,4 V yielded 15-3 (AA) and 154 (AB). Cpe at -1,7 V of 6 equivalents of AN and one equivalent of cyanobutadiene (Ejy2 =... 

The formation of acridine in the reaction of benzyne with anthranil is thought to be a stepwise rather than a concerted (4 + 2)-cycloaddition.221 More interesting are the mercury sulfate-catalyzed cycloadditions of alicyclic ketones to anthranil in boiling xylene, which appear to involve the enol tautomers as indicated in Eq. (10).2 22 The yields of 2,3-cycloalkanoquinolines (163) range from 11% (n = 4) to 39% (n = 5). Phenylacetylene and diethyl maleate yield similar products. 

Excimer formation has been studied in polystyrene and poly(a-alkylstyrenes)189 (PS), poly(vinylcarbazole),139>140 poly-(2-vinylnaphthalene), and poly-(4-vinyl-biphenyl).141 For polystyrene films, David et a/.189 showed that the fluorescence yield increased with increasing crystallinity, at both ambient temperature and 77 K. The contribution of excimer fluorescence yield increased in the sequence atactic (0.7) < atactic oriented (0.60) < isotactic amorphous (0.28) < isotactic crystallized (0.01), with normal yields relative to excimer given in parentheses. Similar results were obtained for poly(vinylcarbazole), PVCZ, although the contribution of excimer fluorescence at 77 was independent of crystallinity. The results can be interpreted in terms of electronic energy migration to low-energy defect sites from which excimer emission can occur. In PVCZ copolymers with fumaronitrile (10), diethyl fumarate (11), and diethyl maleate (12) (Scheme 6),... 

The compatibilizer as such may be compatible with the clay surfaces and hence easily intercalates into the interlayer spacing of the clay platelets and separates the clay platelets, and with bulk polymer it leads to the formation of well-dispersed nanocomposites. The compatibilizer widely used for polypropylene (PP) is maleic anhydride grafted PP (PP-g-MA) [15-16], Other compatibilizers used are diethyl maleate (DEM-g-PP) and polyolefin elastomer grafted maleic anhydride (POE-g-MA),... 

They present the advantage of being cost-eflfective and are easily prepared as their formation does not involve the formation of residual products. Different series of liquid crystalline have been isolated from the reaction of nitric, hydrochloric formic, and tetrafiuoroboric acids with the corresponding alkylimidazoles, pyrrolidines, pyr-idines, or alkylamines. Those based on the imidazolium cation induce a specific stereoselectivity for the catalyzed Diels-Alder condensation reaction of cyclopentadiene and diethyl maleate [2,15]. [The protonated Hiinig base, [NHEt(i-Pr)2][CF3C02], is reported to be an efficient medium for the nitration of arenes. Ohno and Yoshiwaza demonstrated for PILs prepared by neutralization of 1-alkylimidazoles the synergic effect between protonated alkyUmidazoles and palladium, rhodium, or ruthenium catalysts observed in reactions where the presence of a proton is essential for good performance [16]. 

A variety of bases have been used to convert sulphonium salts into ylides. In the case of an unstable ylide such as (1), irreversible generation of the ylide using dimsylsodium in DME resulted in considerable ylide decomposition, whereas the use of a weaker base system, powdered KOH in DMSO, resulted in reversible ylide formation and the maintenance of a lower concentration of ylide." Shono et al. now have published full details of the electrochemical conversion of sulphonium salts into ylides. From the corresponding sulphonium salts in aqueous solution at -1.6 to -2.1 V they were able to generate dimethylsulphonium-2-nitrofluorenylide, -benzylide, and -methylide. The former ylide was isolated while the latter two were trapped by reaction with aldehydes, ketones, and diethyl maleate in yields up to 30%. However, they were accompanied by products probably originating from radicals. 

Alcohols having an acidic hydrogen atom adjacent to the hydroxyl group may undergo dehydration rather than substitution. Thus the reaction of diethyl maleate (29) with phthalimide, DEAD, and TPP gives diethyl fumarate without any detectable formation of the substituted product. With Hydrazoic Acid, however, (29) gives the expected azido succinate (30) in 74% yield (eq 24). Dehydration is regioselective in some cases. ... 

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