Diels-Alder reaction with maleic anhydride

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). 

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). 

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]. 

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. 

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. 

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... 

Various o-quinodimethanes, generated in situ from o-alkenylbenzyltributyl-stannane precursors, have been used to synthesize functionalized polycycles by Diels Alder reaction with maleic anhydride, methylacrylate, dimethylfumarate and N-phenyl maleimide in the presence of electrophiles [37] (Scheme 2.16). 

For a review of Diels-Alder reactions with maleic anhydride see Kloetzel, M.C. Org. React., 1948, 4, 1. 

The salt is a colorless crystalline solid which is virtually insoluble in all common organic solvents. It reacts slowly with chloroform and carbon tetrachloride to give thallium(I) chloride 25), gives a characteristic red coloration with carbon disulfide, and undergoes the Diels-Alder reaction with maleic anhydride 110). It is rapidly decomposed by acids, but is stable to water this latter fact has been interpreted (55) in terms of the small free energy change for the reaction... 

Detonations sometimes occur during Diels-Alder reactions with maleic anhydride. They are explained by the decomposition of this anhydride. 

Figure 7.15 Improvement of the efficiency of rosin as a sizing agent by Diels-Alder reaction with maleic anhydride.

Several other heterohelicenes resist this reaction even when the Friedel-Crafts catalyst (A1C13) is exchanged for FSOjH, 90% HjSO, 40% HF and other strong acids. Some dehydroheterohelicenes have been used to prepare heterocirculenes by a Diels-Alder reaction with maleic anhydride and subsequent hydrolysis and removal of the carboxylic acid groups167). 

Compound 83 is a diene that comprises four carbon atoms of a hexose chain, and it takes part in the Diels-Alder reaction with maleic anhydride to give 86% of the product 84, the stereochemistry of the addition being directed by the acetal ring [42]. 

The Diels-Alder reaction with maleic anhydride is illustrative of the high reactivity and potential utility of this diene. 

Cycloadditions. A cyclic movement of electrons can be drawn for any number of cycloadditions, but not all of them take place. Thus butadiene undergoes a Diels-Alder reaction with maleic anhydride, but ethylene and maleic anhydride do not give a cyclobutane when they are heated together. 

On the other hand, furan has less resonance stabilization (91 kJ mol 0 and undergoes a number of reactions in which the aromatic character is lost. For example, typical of a diene, it undergoes a Diels-Alder reaction with maleic anhydride (Scheme 4.34). 

The hydrogenation of substituted succinic anhydrides such as 65, over platinum oxide at room temperature and 3-4 atmospheres leads to the initial formation of the hydroxy lactone, 66. Further hydrogenation in acetic acid at the same temperature and pressure converts 65 into a 2 1 ratio of the lactone, 67 and the methyl acid, 68. Extended hydrogenation of the anhydride in ethyl acetate gave almost equal amounts of 67 and 68 (Eqn. 18.42). Since anhydrides such as 65 are available from Diels-Alder reactions with maleic anhydride, this procedure has synthetic utility since the hydrogenations take place exclusively on the least hindered carbonyl group of the anhydride. 

R. IV-1, M. C. Kloetzel, The Diels-Alder Reaction with Maleic Anhydride V-2,... 

The reactivity of conjugated double bonds is significantly different from that of isolated double bonds in the polymer backbone of polydienes. This difference can be used for selective chemical modification of the dienes with reactions such as the Diels—Alder reaction. With maleic anhydride as an enophile, selective addition to the terminal pair of conjugated double bonds in a chloroprene oligomer is complete in a few hours to give 102.391... 

Since the initial report that alkyloxazoles participate in Diels-Alder reactions with maleic anhydride,2 extensive efforts have defined the scope and synthetic utility of the [4 + 2] cycloadditions of oxazole derivatives. This work has been the subject of several reviews.3 9... 

One way of avoiding the problem of unnatural polarity is to start with a cheap and readily available 1,4-difunctionalised starting material. A selection is given in Table 25.1. Examples of Friedel-Crafts reactions with some of these compounds were discussed in Chapter 24, and Diels-Alder reactions with maleic anhydride in Chapter 17. 

The method can be simultaneously applied to each atom of interest. An atom that is expected to have a negligible KIE is selected as an internal standard. For example, with the methyl group as the internal standard, the KIE for every other position in isoprene was determined for the Diels-Alder reaction with maleic anhydride. This method is especially useful for the measurement of carbon isotope effects, where normal methods require synthesis of isotopic labeled reactants. 

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