Maleic Diels-Alder with

Maleic acid derivatives, electrolytic reduction, 42 Maleic acid salts, Diels-Alder with PVC, 472 Maleic acid terpolymers, 296 Maleic anhydride, perdeuterated, styrene copolymerization, 366... 

A major contribution of naval stores products to the coatings industry occurred in the 1920s and 1930s with the production of alkyd resins from the reaction of polyhydric alcohols, viz., glycerol and pentaerythritol with rosin-maleic and terpene-maleic Diels-Alder condensation products. The name alkyd was coined by Kienle (Simonsen et al, 1947-1952) in 1927. 

Since the octatetrene contains two CH CH-CH CH units, it will readily combine with two molecules of maleic anhydride and other adducts by the Diels-Alder reaction (p. 292). 

The balance between aromatic and aUphatic reactivity is affected by the type of substituents on the ring. Furan functions as a diene in the Diels-Alder reaction. With maleic anhydride, furan readily forms 7-oxabicyclo [2.2.1]hept-5-ene-2,3-dicarboxyhc anhydride in excellent yield [5426-09-5] (4). 

Maleic anhydride has been used in many Diels-Alder reactions (29), and the kinetics of its reaction with isoprene have been taken as proof of the essentially transoid stmcture of isoprene monomer (30). The Diels-Alder reaction of isoprene with chloromaleic anhydride has been analy2ed using gas chromatography (31). Reactions with other reactive hydrocarbons have been studied, eg, the reaction with cyclopentadiene yields 2-isopropenylbicyclo[2.2.1]hept-5-ene (32). Isoprene may function both as diene and dienophile in Diels-Alder reactions to form dimers. 

V- Alkylpyrroles react with maleic anhydride to give the electrophilic substitution product (7) and not the Diels-Alder addition product found for... 

Aqueous ring-opening metathesis polymerization (ROMP) was first described in 1989 (90) and it has been appHed to maleic anhydride (91). Furan [110-00-9] reacts in a Diels-Alder reaction with maleic anhydride to give exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3—dicarboxylate anhydride [6118-51 -0] (24). The condensed product is treated with a soluble mthenium(Ill) [7440-18-8] catalyst in water to give upon acidification the polymer (25). Several apphcations for this new copolymer have been suggested (91). 

Removal of maleic and fumaric acids from the cmde malononitrile by fractional distillation is impractical because the boiling points differ only slightly. The impurities are therefore converted into high boiling compounds in a conventional reactor by means of a Diels-Alder reaction with a 1,3-diene. The volatile and nonvolatile by-products are finally removed by two vacuum distillations. The by-products are burned. The yield of malononitrile amounts to 66% based on cyanogen chloride or acetonitrile. 

The cleavage of dicyclopentadiene into cyclopentadiene can be accomplished at temperatures above 160°C, producing the heterocycHc Diels-Alder maleic addition product, which opens to the diacid. This product can be esterified with propylene glycol to produce resins that demonstrate enhanced resihence and thermooxidative resistance suitable for molded electrical components. 

Vitamin D2 reacted with maleic anhydride to give a mono Diels-Alder adduct, which hydrolyzed to yield a dicarboxyhc acid. Acetylation of the alcohols, esterification of carboxyHc acids, and hydrogenation gave a compound that, when ozonized, gave a saturated ketone, This molecule... 

Conjugation as well as geometric and positional isomerization occur when an alkadienoic acid such as linoleic acid is treated with a strong base at an elevated temperature. CycHc fatty acids result from isomerization of linolenic acid ia strong base at about 250°C (58). Conjugated fatty acids undergo the Diels-Alder reaction with many dienophiles including ethylene, propylene, acryUc acid, and maleic anhydride. 

Cyclopentadiene contains conjugated double bonds and an active methylene group and can thus undergo a Diels-Alder diene addition reaction with almost any unsaturated compound, eg, olefins, acetylene, maleic anhydride, etc. The number of its derivatives is extensive only the reactions and derivatives considered most important are discussed. 

Flame Retardants. Although the use of chlorinated derivatives of DCPD has been restricted in the pesticide area, some are widely used in flame and fire retardant chemicals (see Flame retardants). The starting material is the fliUy chlorinated DCPD cracked to monomeric hexachlorocyclopentadiene, which is then converted via a Diels-Alder reaction with maleic anhydride to a reactive bicycHc anhydride (9), known as chlorendic anhydride [115-27-5]. 

Dicyclopentadienedicarboxyhc acid can undergo a Diels-Alder reaction in the presence of a stoichiometric amount of a dienophile at 140—190°C to give an adduct of the monomeric acid. The yield of adduct is usually 75—95%. A large number of polyfunctional compounds are easily prepared in this manner. The reaction with maleic anhydride gives a tribasic acid. 

Benzo[Z)]furans and indoles do not take part in Diels-Alder reactions but 2-vinyl-benzo[Z)]furan and 2- and 3-vinylindoles give adducts involving the exocyclic double bond. In contrast, the benzo[c]-fused heterocycles function as highly reactive dienes in [4 + 2] cycloaddition reactions. Thus benzo[c]furan, isoindole (benzo[c]pyrrole) and benzo[c]thiophene all yield Diels-Alder adducts (137) with maleic anhydride. Adducts of this type are used to characterize these unstable molecules and in a similar way benzo[c]selenophene, which polymerizes on attempted isolation, was characterized by formation of an adduct with tetracyanoethylene (76JA867). 

Initial materials of this super-tough type were blends of nylon 66 with an ionomer resin (see Chapter 11). More recent materials are understood to be blends of nylon 66 with a modified ethylene-propylene-diene terpolymer rubber (EPDM rubber—also see Chapter 11). One such modification involves treatment of the rubber with maleic anhydride, this reacting by a Diels—Alder or other... 

Soon after the discovery of the addition reaction between diene-ophiles and dienes which now bears their names, Diels and Alder extended their investigations to include potential heterocyclic dienes. In 1929 the first compound investigated, furan, was observed to combine with maleic anhydride, like butadiene in a typical Diels-Alder reaction, across the 2,5-positions yielding a 1 1 molar adduct... 

Acetylenedicarboxylic acid is known to combine with a number of pyrroles but only in the case of 1-benzylpyrrole have the products been rigorously examined. Mandell and Blanchard showed that in this case a mixture of the maleic anhydride (35), the fumaric acid (36), and the Diels-Alder type adduct (38) was formed. 

Dimethylquinoxaline (303) has been reported to undergo a Diels-Alder reaction with maleic anhydride to give 304, 305 having been postulated to be the reactive form. However, attempted confirmation of this unexpected result has shown that 304 is not the correct structure of the reaction product. " In 1931, other chemical evidence was advanced in support of structure 305,but it would no longer be considered valid. 

Isoindole itself gives normal Diels-Alder addition products, (107 and 108), with maleic anhydride and A-phcnylmaleimide, these derivatives constituting the main evidence for forma,tion of the parent substance. 2-Alkyl- and 2-arylisoindoles also give normal addition products with these two dienophiles.Although only one product is generally isolated, it seems likely, in view of the known tendency of several Diels-Alder adducts of isoindoles to dissociate to their components (see below), that both exo and endo stereoisomers might be formed in certain cases. The reaction between 2-p-tolyl-isoindole and A-phenylmaleimide has been shown to give both e,xo (109) and endo (110) addition products. ... 

In the case of 1,3-diphenylisoindole (29), Diels-Alder addition with maleic anhydride is readily reversible, and the position of equilibrium is found to be markedly dependent on the solvent. In ether, for example, the expected adduet (117) is formed in 72% yield, whereas in aeetonitrile solution the adduet is almost completely dissociated to its components. Similarly, the addition product (118) of maleic anhydride and l,3-diphenyl-2-methjdi.soindole is found to be completely dissociated on warming in methanol. The Diels-Alder products (119 and 120) formed by the addition of dimethyl acetylene-dicarboxylate and benzyne respectively to 1,3-diphcnylisoindole, show no tendency to revert to starting materials. An attempt to extrude carbethoxynitrene by thermal and photochemical methods from (121), prepared from the adduct (120) by treatment with butyl-lithium followed by ethyl chloroform ate, was unsuccessful. 

Benz[/]isoindole (125), recently prepared from the p-toluene-sulfonyl derivative (124), proved to be too unstable for isolation, but eould be trapped in solution as the Diels-Alder adduct (127). The corresponding 1-phenyl derivative (126) was also prepared and, aecording to spectral measurements, reacts with maleic anhydride to give the product (128) derived by additive substitution. This subsequently rearranged to the adduct (129). The same behavior is observed in the reaction of (126) with V-phenylmaleimide. This provides the first clear indication that substitution products from isoindole derivatives and dienophiles can be converted into the normal addition products. 

Dihydropyridines 8 react with dienophiles such as A -phenyl maleimide (2) and l,2,4-triazoline-3,5-dione 9 to give the Diels-Alder adducts 10 and 11, respectively (76JHC481). Fowler observed that when a mixture of 1,2- and 1,4-dihydropyridines was treated with maleic anhydride (12), only 1,2-dihydro-pyridines yielded the Diels-Alder adducts 13, whereas the 1,4-dihydropyridines showed no reactivity with 12 (72JOC1321) (Scheme 1). 

Dimethylquinoxaline undergoes reaction with typical dienophiles such as maleic anhydride, p-benzoquinone, and AT-phenylmaleimide. The products were formulated as Diels-Alder adducts primarily since analogous products were not isolated from reactions with other quin-... 

Compound 5 can be trapped through a Diels-Alder reaction with maleic anhydride and thus be shown to be an intermediate. Further evidence for a mechanism involving two subsequent allyl conversions has been provided by experiments with " C-labeled substrates. 

The Diels-Alder reaction,is a cycloaddition reaction of a conjugated diene with a double or triple bond (the dienophile) it is one of the most important reactions in organic chemistry. For instance an electron-rich diene 1 reacts with an electron-poor dienophile 2 (e.g. an alkene bearing an electron-withdrawing substituent Z) to yield the unsaturated six-membered ring product 3. An illustrative example is the reaction of butadiene 1 with maleic anhydride 4 ... 

A domino reaction,in this case consisting of an inter- and an intramolecular Diels-Alder reaction, is a key step in the synthesis of the hydrocarbon pago-dane 30, reported by Prinzbach et al When the bis-diQnQ 27 is treated with maleic anhydride 4, an initial intermolecular reaction leads to the intermediate product 28, which cannot be isolated, but rather reacts intramolecularly to give the pagodane precursor 29 ... 

The use of lead tetraacetate to carry out oxidative bisdecarboxylation of diacids has been found to be a highly useful procedure when used in conjunction with the Diels-Alder addition of maleic anhydride to dienes, the latter process providing a ready source of 1,2-dicarboxylic acids. The general pattern is illustrated in the reaction... 

Cyclic 1,3-diacetoxy-l,3-dienes can be generated in situ from cyclic 1,3-diketones under the influence of isopropenyl acetate. The dienes then undergo Diels-Alder reactions with maleic anhydride giving as products 1-acetoxybicycloalkane dicarboxylic anhydride derivatives (10). The procedure is also successful with cyclic 1,2- and 1,4-diketones as well as cyclic a,j3-unsaturated ketones. The products, after hydrolysis to... 

Endo products result from Diels-Alder reactions because the amount of orbital overlap between diene and dienophile is greater when the reactants lie directly on top of one another so that the electron-withdratving substituent on the dienophile is underneath the diene. In the reaction of 1,3-cyclopentadiene with maleic anhydride, for instance, the following result is obtained ... 

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