Diels-Alder reaction product

A number of special purpose resins are available which employ somewhat unusual acids and diluents. A resin of improved heat resistance is obtained by using Nadic anhydride, the Diels-Alder reaction product of cyclopentadiene and maleic anhydride Figure 25.5). 

Studies also show that by using catalyst 76a or 78 derived from one single chiral tetraol with the same absolute configuration, both enantiomers of the Diels-Alder reaction product can be obtained. For example, reaction of 2-methyl-... 

Oikawa M, Ikoma M, Sasaki M (2005) Parallel synthesis of tandem Ugi/Diels-Alder reaction products on a soluble polymer support directed toward split-pool realization of a small molecule library. Tetrahedron Lett 46 415-418... 

Studies by Teplyakov et al. provided the experimental evidence for the formation of the Diels-Alder reaction product at the Si(100)-2 x 1 surface [239,240]. A combination of surface-sensitive techniques was applied to make the assignment, including surface infrared (vibrational) spectroscopy, thermal desorption studies, and synchrotron-based X-ray absorption spectroscopy. Vibrational spectroscopy in particular provides a molecular fingerprint and is useful in identifying bonding and structure in the adsorbed molecules. An analysis of the vibrational spectra of adsorbed butadiene on Si(100)-2 x 1 in which several isotopic forms of butadiene (i.e., some of the H atoms were substituted with D atoms) were compared showed that the majority of butadiene molecules formed the Diels-Alder reaction product at the surface. Very good agreement was also found between the experimental vibrational spectra obtained by Teplyakov et al. [239,240] and frequencies calculated for the Diels-Alder surface adduct by Konecny and Doren [237,238]. 

K. M. Sun, R. Guiliano, and B. Fraser-Reid, Diacetone glucose derived dienes in Diels-Alder reactions. Products and transformations, J. Org. Chem. 50 4114 (1985). 

The Diels-Alder reaction can be used for asymmetric synthesis of p,y-disubstituted glutamic acids.[98] Fully protected dehydroglutaminol 63 serves as a dienophile and, after a series of deprotection and oxidation of the Diels-Alder reaction product, disubstituted glutamic acids 68A and 68B (Scheme 22) can be obtained. 

The following cycloaliphatic compounds are suitable as flame retardants in polyolefins hexabromo-cyclododecane and bromine-containing Diels-Alder reaction products based on hexachloro-... 

It should be noted that cyclooctatetraene is a tub-shaped molecule, therefore, the double bonds in it are not conjugated enough to react with maleic anhydride. As a result, the Diels—Alder reaction products shown in option (a) wiU not be obtained. 

The photolysis of the 1,3-butadiene (164) with P4 led to the Diels-Alder reaction products (165) in good yields. This method can incorporate phosphorus atoms into organic molecules from P4. 

Modifying components other than phthalic anhydride are frequently used in the preparation of unsaturated polyesters in order to impart special properties to the final product. Adipic and sebacic acids are employed to give flexible materials and isophthalic acid (VI) is used for tough products with higher heat distortion temperatures. The use of e (iomethylenetetrahydrophthalic anhydride ( nadic anhydride ) (VII), the Diels-Alder reaction product of cyclopentadiene and maleic anhydride, leads to a substantial improvement in heat resistance. Flame resistant materials are obtained by the use of chlorinated acids and anhydrides, e.g., tetrachlorophthalic anhydride (VIII) and chlorendic acid (HET acid) (IX). The latter is prepared by the Diels-Alder reaction of hexachlorocyclopentadiene and maleic anhydride the initial product is chlorendic anhydride but this rapidly absorbs water from the air to give the acid. 

The first indication of conditions that would favor the formation of the pyrrolidine found in the flinderoles resulted from the use of anhydrous HCI in methanol. These protic conditions resulted in a 2 1 bias in formal [2+31-cycloaddition to Diels-Alder reaction products. Fewer than 6 equiv. of acid caused a sluggish reaction, and a higher concentrafiOTi did not alter the ratio of products greatly. Nevertheless, this result provided hope that buffered or more weakly acidic conditions would avoid the interconversion of dimeric products that favors isoborreverine formation. We sought other conditions empirically that would provide the flinderoles though kinetic reaction control. 

Narrowing Diels-Alder reaction products to one enantiomer requires a chiral influence either as part of the dienophile [40], as in Equation 8.29 [41], or as part of a Lewis acid catalyst [42] as in Equation 8.30 [43]. In many Diels-Alder reactions, steric hindrance or intramolecular restrictions limit the number of isomers. Altogether, stereospecificity, regiospecificity, and endo/exo control make most Diels-Alder reactions quite practical. 

As mentioned in the previous section, substituted norbornadienes can proceed [2+2] cycloaddition with highly reactive dienophiles (maleic imide or strained alkene) in the presence of a nickel (0) catalyst leading to the formation of cyclobutane derivatives. With less reactive dienophiles, the reaction seems to be prone to [2+ 2+ 2] cycloaddition giving homo-Diels-Alder reaction products. These two types of reactions appear to be competitive in certain cases to give a mixture of products [130-133]. 

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