Dienophiles maleic anhydride

The product of a Diels-Alder cycloaddition always contains one more ring than was present m the reactants The dienophile maleic anhydride contains one ring so the product of Its addition to a diene contains two... 

In order to smdy the effect of perturbation arising from spiro-conjugation on the chemical reactivities, in particular the facial selectivities, sterically unbiased dienes (96 and 97) based on fluorenes in spiro geometry have been synthesized [165]. These dienes react as Diels-Alder dienes with several dienophiles (maleic anhydride (MA), A-phenylmaleimide (PMI), A-phenyl-l,3,5-triazoUne-2,4-dione (PTD) and iV-methyl-l,3,5-triazoline-2,4-dione (MTD)). 

Thermal cracking at 150°C of the dimer (mixed isomers) of the silole in presence of reactive dienophiles (maleic anhydride, tetracyanoethylene or dimethyl acetylenedicarboxylate) inevitably produced violent explosions arising from exothermic Diels-Alder reactions. 

Olah et al.902 demonstrated in 1979 that Nafion-H is able to catalyze Diels-Alder reaction of anthracene with a number of dienophile (maleic anhydride [Eq. (5.329)], para-benzoquinone, dimethyl maleate, dimethyl fumarate) in chloroform or benzene... 

What products are obtained when 1-methylcyclopenta-1,3-diene reacts as a diene with the dienophile maleic anhydride ... 

A v/c-dihaloadamantane undergoes the intermolecular reductive dimerization via unstable adamantene species to give stereoisomeric products in 80-90% yields, as in Eq. (34) [240]. Cathodic reduction of or, or -dibromo-l,2-dialkylbenzenes in the presence of dienophiles (maleic anhydride, etc.) and hinderd dienophiles provides diels-Alder adducts stereoselectively [241,242]. In this reaction, the dienophiles play a duel role as mediators... 

Phenylphosphole and 3-methyl-1-phenylphosphole also gave such adducts, but they were difficult to separate from some accompanying P-oxides. Other dienophiles (maleic anhydride, tetra-cyanoethylene, benzoquinone) were not useful in this process. 

Deuterium isotope effects have been studied for the Diels-Alder reactions between hexadeuterio-monosubstituted cyclo-octatetraenes (283) and several reactive dieno-philes leading to adducts (284). With dicyanomaleimide, isomerization of the cyclo-octatetraene to the bicyclo[4,2,0]octa-2,4,7-triene is the rate-determining step, but with the less reactive dienophiles (maleic anhydride and tetracyanoethylene) larger... 

Unsubstituted glycal 49 underwent cycloaddition reaction with a sp dienophile (maleic anhydride) in refluxing toluene to give a mixture of two epimeric compounds arising from an expected endo attack. The 7 3 ratio in stereoadducts 51 and 52 clearly indicates an stereochemical preference inherent to the pyranosidic substrate (vide supra). 

The Diels-Alder adducts 2 and 6 retain the anhydride function that was originally present in the dienophile, maleic anhydride. As a rule, this functionality is unstable in the presence of water even at pH 7 and hydrolyzes to a dicarboxylic acid according to the general sequence outlined in Scheme 12.1. This process is initiated by nucleophilic attack of water on the carbonyl function, followed by cleavage of a C-O bond of the anhydride. Because anhydrides are reactive toward water, it is important that the apparatus and reagents you use are dry to maximize the yield of cycloadduct. You may be instructed to prepare the dicarboxylic acids 7 and 8 by intentional hydrolysis of the corresponding anhydrides. Protocols for doing so are included in Part C of the experimental procedures. 

The conclusion as to the nonconcerted character of the [4 -h 2]-cycloaddition reactions and sharp asynchronization of the process of formation of the -bonds in the course of the reaction has been borne out by a careful kinetical analysis, performed by Dewar, of reactions of typical dienophile maleic anhydride with a number of furane derivatives as well as by critical examination of other experimental data on the Diels-Alder reactions [29,35]. A similar conclusion has also been drawn for the [4 + l]-cycloaddition reaction [31], for some other... 

Figure 13.13 Diels-Alder reaction of cyclopentadiene and maleic anhydride, (a) When the highest occupied molecular orbital (HOMO) of the diene (cyclopentadiene) interacts with the lowest unoccupied molecular orbital (LUMO) of the dienophile (maleic anhydride), favorable secondary orbital interactions occur involving orbitals of the dienophile. (b) This interaction is indicated by the purple plane. Favorable overlap of secondary orbitals (indicated by the green plane) leads to a preference for the endo transition state shown.

In this chapter, we will consider the one reaction of maleic anhydride that has been most investigated in the last half-century. Of historical significance is the formation of a cyclohexene derivative 3 from a conjugated diene (butadiene) 2 and a dienophile (maleic anhydride, MA) 1 as reported... 

The room temperature cycloaddition of olefins to furans at 15 000 atm has been reported. Prior to this work, only reactive dienophiles (maleic anhydride, dimethyl-acetylene dicarboxylate) gave good yields of adducts, but this study has shown that weaker dienophiles can be employed (Scheme 38). ... 

---