By the Diels-Alder reaction

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). 

Since cyclohexenes can also be made by the Diels-Alder reaction (frames 5-8) we have access to a wide range of 1,6-dicarbonyl compounds. How about TM 196 ... 

We must next disconnect the six-membered ring and the only way we know to set up these chiral centres specifically is by the Diels-Alder reaction. Two alternative sites for the double bond are possible if we convert our NHi to give the necessary activating group (NOi)... 

Isoprene is highly reactive both as a diene and through its allyhc hydrogens, and its reactions are similar to those of butadiene (qv) (8). Apart from polymerisation, the most widely investigated isoprene reactions are the formation of six-membered rings by the Diels-Alder reaction ... 

A continuous process has been described for the manufacture of anthraquinone by the Diels-Alder reaction (49). 

BMI also reacts with dienes to form Diels-Alder adducts [12]. When BMI reacts with a a,(n-biscyclopentadienyl compound or other bis-diene resin, the bis-maleimide chain is extended by the Diels-Alder reaction. Bis-maleimide, chain extended with bis-diene, is not used in adhesives. However, as the Diels-Alder reaction is reversible, there may be a possibility of recyclability of the cured resin by depolymerization of the backbone (Fig. 6). 

Nitroethene rmdergoes rapid cycloaddidon to l,3-dienes the subsequent Nef reacdon gives cyclohexenones, which are formally produced by the Diels-Alder reaction of ketene v/ith... 

Can polymerise, but its main danger iies in its propensity to dimerise by the Diels-Alder reaction. This reaction takes piace at a temperature starting at 0-40°C, under pressure, if the dimerisation is not controlled, the storage equipments temperature and pressure rise very quickly, which leads to their destruction. Storage temperatures of -80°C have been recommended. 

The tricyclic fused heterocyclic system 236 containing a phosphorus atom was constructed by the Diels-Alder reaction. Thus, diazaphospholopyridine 235 was treated with 2,3-dimethylbutadiene in the presence of sulfur or selenium to give the product 236 (Equation 27) <2002JOC9162, 2002T1573, 2005T10521>. 

The partially hydrogenated phenanthrene derivative 18 (entry 4) is a very moderate diene due to the steric crowding caused by the substituents and the anulated rings, and it reacts even with highly reactive dienophiles such as maleic anhydride (MA) or N-phenylmaleic imide only at high pressure. The minor product 20 in the reaction with MA obviously stems from diene 21. This can be explained by a double-bond isomerization 18 - 21 prior to the cycloaddition, certainly catalyzed by traces of acid present in the MA. In the absence of acid only the Diels-Alder adduct 22 derived from diene 18 was observed. In the reaction of diene 23 with MA (entry 5) a similar sequence of steps was observed. A [1,5] shift of the C—O bond in 23, again certainly acid-catalyzed, produces the diene 26 followed by the Diels-Alder reaction with MA to give 24 and 25. 

Chiral LA are rarely used in the constmction of chiral six-membered cyclic nitronates by the Diels-Alder reaction of olehns with a-nitoralkenes (96, 158), in spite of the potential efficiency of the process. Apparently, this is associated with the absence of known common features of the process and, as a consequence, with the necessity to perform special investigations for optimization in each particular case. 

In this chapter we wish to review the collected evidence for the astonishing effects of water on reactivities and selectivities as exemplified by the Diels-Alder reactions of dienes. Examples of Lewis acid and micellar catalysis in aqueous media are also presented. Finally, the newest computational investigations including solvent effects on Diels-Alder reactions are put forward in order to rationalize some of the remarkable observations. 

All the chlorinated hydrocarbons belonging to this second group of compounds, once used in large amounts, have been banned for use in the U.S. since 1974. They are made by the Diels-Alder reaction, named after two chemists who won the Nobel Prize in 1950 for the discovery of this important reaction. The synthesis of the important insecticides chlordane, heptachlor, aldrin, dieldrin, and endrin are summarized in Fig. 20.4. 

Norbornene can be prepared by the Diels-Alder reaction of ethylene with dicyclopentadiene.4 It can be purchased from Matheson Coleman and Bell or the Aldrich Chemical Company, Inc. 

Cyclopentene is readily available as a byproduct in the ethylene production. Norbornene 2-ethylhexyl carboxylate is obtained by the Diels-Alder reaction of 2-ethylhexyl acrylate with cyclopenta-diene (5). Norbornene isobornyl carboxylate, norbornene phen-oxyethyl carboxylate, and other related monomers are synthesized according to the same route. Polymers obtained from these esters exhibit excellent properties in terms of controlling the crosslinking density, the associated product modulus, and the glass transition temperature (Tg), thus allowing tailoring the properties of elastomers, plastics and composites. Other suitable monomers are summarized in Table 1.1 and sketched in Figure 1.2. 

A dinorbornenyl dicarboxylate ester (DNBDE) is synthesized by the Diels-Alder reaction of cyclopentadiene with diacrylates, as shown in Figure 1.10. Alternatively, a DNBDE may be synthesized... 

Whenever a ring has to be constructed, you should consider the possibility of cycloaddition reactions, especially [4 + 2] cycloaddition by the Diels-Alder reaction. A first glance at 9, written in the usual sawhorse-perspective formula, might lead to overlooking the possibility of constructing the skeleton by [4 + 2] addition, because the compound seems only to be made up of five-membered rings. If the structure is rewritten as 10, the six-membered ring stands out much more clearly ... 

The cycloaddition reactions that we have discussed so far in this chapter ([2 + 2], [4 + 2], etc.) have involved ring formation by bringing two unsaturated molecules together. Thus [4 -r 2] addition is represented by the Diels-Alder reaction of ethene and 1,3-butadiene ... 

A general method for the preparation of the title compounds has been developed only recently. Triply substituted l-telluracyclohex-3-enes 19 were synthesized in moderate yields by the Diels-Alder reaction of telluro-aldehydes 20 with 2,3-dimethylbutadiene (89AG181, 89JA8749). 

Given the structure of a cyclic compound that can be synthesized by the Diels-Alder reaction, deduce the structures of the required diene and dienophile. 

Now, how about making the ketone 47 by the Diels-Alder reaction Direct disconnection (arrows on 47) leads to a good diene 45 but an unacceptable dienophile 46. This is a ketene and they don t do Diels-Alder reactions. You will see in chapter 33 what they can do. But if you change the ketone into a nitro group 48, the problem disappears. 

We have expanded our collection of stereoselective reactions even more in the making of alkenes by the Wittig reaction (chapter 15), from acetylenes (chapter 16), by thermodynamic control in enone synthesis (chapters 18 and 19) and in sigmatropic rearrangements (chapter 35). We have seen that such E- or Z-alkenes can be transformed into three-dimensional stereochemistry by the Diels-Alder reaction (chapter 17), by electrophilic addition (chapters 23 and 30), by carbene insertion (chapter 30) and by cycloadditions to make four-membered rings (chapters 32 and 33). 

Benzoyl-4-methylbicyclo[2.2.2]oct-5-en-2-one 71, prepared by the Diels-Alder reaction of 2-trimethylsioxy-4-methyl-l, 3-cydohexadiene with benzoylethyne, underwent ODPM rearrangement in the absence of a sensitizer to give 72 in good yield (Scheme 4.29). The irradiation of 72 in 40% triethylamine (TEA)-methanol gave a bicyclo[3.2.1]octanone 73 in 86% yield. On direct irradiation, a one-pot conversion... 

The indene-derived group. At the Velsicol Chemical Corporation in Chicago in 19 3, Dr. Julius Hyman was seeking new uses for the cyclopentadiene which was a by-product of U.S. synthetic rubber production and was already used by Velsicol for the manufacture of resins and varnishes by the Diels-Alder reaction (6). A literature search revealed Straus s 1930 synthesis of hexachlorocyclopentadiene ( hex ) and, since chlorinated dienes are frequently rather inert, Hyman was interested to determine if hex would participate in the Diels-Alder reaction, either with itself or with cyclopentadiene. 

An unsaturated bicyclic lactam, 2-azabicyclo[2.2.1]hept-5-en-3-one (77), which was synthesized by the Diels-Alder reaction of tosyl cyanide with cyclopentadiene... 

Stille, J. K., and L. Plummer Polymerization by the Diels-Alder Reaction. Abstracts of Papers Presented at the 136th Meeting of the American Chemical Society, Atlantic City, N. J., Sept. 13—18 (1959), p. 3T. 

Polymerization by the Diels-Alder Reaction. J. Oig. Chem. (in press.). 

In addition, a small amount of a six-membered ring compound is formed by the Diels-Alder reaction as a third product to give T, 4,4,5-tri-fluoro-1-cyclohexene. It is likely that both concerted and biradical mechanisms are involved [123]. 

In the 1950s two very effective pesticides were launched and their names were Dieldrin and Aldrin. As you may guess they were made by the Diels-Alder reaction. Aldrin is derived from two consecutive Diels-Alder reactions. In the first, cyclopentadiene reacts with acetylene to give a simple symmetrical cage molecule norbomadiene ... 

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