Diels-Alder reaction cycloaddition reaction

Figure 30.9 Interaction of diene LUMO and alkene HOMO in a suprafacial 14 - 2] cycloaddition reaction (Diels-Alder reaction).

This chapter deals with [2 + 2], [4 + 2], [6 + 4], [8 + 2] and [2 + 2 + 2] cycloaddition reactions of dienes and polyenes. Most attention is devoted to the [4 + 2] cycloaddition reaction (Diels-Alder reaction) which is likely to be the most studied reaction in the chemical literature. 

Annelation (see Cycloaddition reactions, Diels-Alder reactions, Ring-forming reactions)... 

Gollnick, K. and G. O. Schenk. 1967. In Hamer, J., Ed. 1,4-Cycloaddition Reactions Diels-Alder Reaction in Heterocyclic Synthesis. (New York, NY Academic Press), pp. 255-300. 

In this subchapter, I summarized the intermolecular two-component cycloaddition reactions, which are able to construct benzenoid aromatic rings. Four types of transition metal-catalyzed [4-r2] cycloaddition reactions (Diels-Alder reactions, reactions of enynes with alkynes, reactions via pyrylium intermediates, and reactions via acylmetallacycles) are described. 

Cycloaddition Reactions. Diels-Alder reactions with maleic anhydride (eq 4) lead to cyclic allylsilanes, which can undergo further interesting elaborations. ... 

Cycloaddition Reactions (Diels-Alder Type Reactions). 271... 

Scheme 4 Access to various a,/ -unsaturated carbene complexes from alkynylcarbene complexes 23. A 1,3-Dipolar cycloaddition. B Diels-Alder reaction. C Ene reaction. D [2+2] Cycloaddition. E Michael-type addition followed by cyclization. F Michael-type additions...

Takeshita H., Mori A., Tian G. R. Carbon-Carbon Double Bond Formation by Means of High-Pressure Cycloaddition-Retro-Diels-Alder Reaction Between 2,3-Bis(Methoxycarbonyl)-7-Oxanorbornadiene and Dienes Yuki Gosei Kagaku Kyo-kaishi 1990 48 132-143... 

Peer-reviewed journals [18] sections in review [89]. A Knoevenagel condensation is described imder 4.8.2 Cycloadditions - The Diels-Alder Reaction, since both reactions were performed combined in a domino-type process. 

Cycloadditions - Photo-Diels-Alder Reactions Using Oxygen... 

The ability of the Si=P bond to serve as a dienophile for a [2+4]-cycloaddition (hetero-Diels-Alder reaction) has been verified by the reaction of 15a with cyclopentadiene (Eq. 10).14 The components react at 60°C in benzene to give a quantitative yield of 25, which was isolated as a colorless solid. Interestingly, a Br0nsted acid (C—H)/base (Si=P) reaction, as in the case of 15a and phenylacetylene, was not observed. In the mass spectrum of25, the molecular peak but also the free phosphasilene 15a+ have been detected. Similar behavior was observed for related ad-... 

Intermolecular cycloadditions or Diels-Alder reactions have proved to be a successful route to several valuable intermediates for natural product syntheses. In creating new chiral centers, most of these reactions apply single asymmetric induction. As mentioned in Chapter 3, in the asymmetric synthesis of the octa-hydronaphthalene fragment, the Roush reaction is used twice. Subsequent intramolecular cyclization leads to the key intermediate, the aglycones, of several natural antitumor antibiotics. On the other hand, the Diels-Alder reaction of a dienophile-bearing chiral auxiliary can also be used intramolecularly to build... 

The second well-known and much-used carbon-carbon bond forming reaction is a [4 + 2]-cycloaddition, the Diels Alder reaction. Very many chiral Lewis acid catalysts have been used to promote this reaction and a pot-pourri of organo-aluminium, -boron and -copper catalysts are described, in brief, below. 

Perhaps the most successful application of Fukui function and local softness is in the elucidation of the region-selective behavior of different types of pericyclic reactions including the 1,3-dipolar cycloadditions (13DC), Diels-Alder reactions, etc. These reactions can be represented as shown in Scheme 12.4. Considering the concerted approach of the two reactants A and B, there are two possible modes of addition as shown in Pathway-I and Pathway-II. 

An important catalyst-substrate intermediate that applies to both the TiCl2-TADDOLate catalyzed 1,3-dipolar cycloadditions and Diels-Alder reactions has been isolated and characterized (353). The crystalline compound 248 has been characterized by X-ray analysis, showing that the oxazolidinone is coordinated to the titanium center in a bidentate fashion (Scheme 12.75). The four oxygen atoms. 

Cyclobutadienes represent very reactive alkenes that undergo both [2 + 2] as well as [4 + 2] cycloadditions. Both the cyclodimerizations, mixed [2 + 2] cycloadditions and Diels-Alder reactions of these reactive species have been reviewed (see Houben-Weyl, Vols. 4/4, p 231 and E 17 f, Section 10B). In most instances the initially formed cyclodimer is tricyclo[4.2.0.02-5]octa-3,7-diene (36) and has the all cis-syn configuration. This is attributed to the concerted [4n -I- 2n] cycloaddition mechanism in which stereochemical control is affected by secondary orbital interactions. 

Cycloadditions, or Diels-Alder reactions, on silicon The other common type of cycloaddition reaction in organic chemistry is the [4 +... 

Three reactions are of great importance [2 + 2] cycloaddition, 1,3-dipolar cycloaddition and Diels-Alder reactions ([4 + 2] cycloadditions), which lead to four-, five- and six-membered rings, respectively. [3 + 3] Cycloadditions are known (see Section 4.3.8.2) but are of less importance. 

The addition of DMAD to the isoquinolinium betaine 369 gave the interesting cycloadduct 370.397 A 1,4-cycloaddition and Diels-Alder reaction took place when 4-dithiocarboxyl-2,3-dimethylisoquinolinium betaine (371) was heated with DMAD in DMF for 20 to 30 minutes at 100°. The initial product was thought to be 372, which added a second mole of ester yielding 373.398... 

The only pericyclic reactions we have used so far have been cycloadditions the Diels-Alder reaction in chapter 17 and 2 + 2 cycloadditions in chapter 33. Electrocyclic and sigmatropic reactions are also used in synthesis and, as each is the basis for a synthesis of five-membered rings, they are grouped together here. 

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