Diels-Adler cycloaddition

When 2D or 3D PAHs are considered then the choice becomes much larger. An exhaustive review on the advances in the synthesis of polycyclic aromatic compounds can be found in Harvey, 2004. The most used strategies are flash vacuum pyrolysis, cross-coupling, oxidative photocyclization, Diels-Adler cycloaddition, etc. 

Patent Conjugation of Biomolecules Using Diels-Adler Cycloaddition... 

Seitz G, Hoferichter R, Mohr R (1989) Imidazoles, oxazole and N-methylpyrazole as dieno-philes in the Diels-Adler-cycloaddition with inverse electron demand. Arch Pharm 322 415-417... 

Manzamine alkaloids can be isolated from marine sponges. They often contain /3-carboline. This group has a diverse range of bioactivities. It also has its own way of establishing its structures. An intramolecular Diels-Adler reaction for manzamines has been proposed. The a is bisdihydropyridine (derived probably from amonia), and the (3 is intramolecular cycloaddition in a pentacyclic... 

Diene A is similar m structure to 1,3-cydohexadiene. which reacts well in Diels-Alder cycloadditions O ablc 14- IX In diene B, however, the ends of the diene are locked in a zigzag conformation (called "s-traas") that puts the end carbons too far apart to bond to the two alkene carbons of a dienophile. Figure 14-9 illustrates how the Diels-Alder reaction involves a diene in a U-shaped conformation (called s-cis ), which puts its end carbons close together. Dienes (like B) that cannot achieve this conformation will not participate with dienophiles in Diels-Adler reactions. 

Fig. 3 Houk s model for the transition state of the synchronous Diels-Adler addition and its application to the cycloadditions of 2,3-dimeth)didenebicyclo[2.2.1]heptane...

We decided to investigate one final substrate that contained our desired side chain for the intramolecular Diels-Alder cycloaddition as well as a small and removable cyano group. Our synthesis is outlined in Scheme 11. Phenol 53 was alkylated with chloroacetonitrile, then condensed to form 2-cyano benzo-furan 54. Subsequent quatemarization to 56 was accomplished with sodium hydride and a bromocrotcMiate (55) electrophile. Following phenol ether deprotection and reduction of the benzylic ketone with sodium borohydride, we were in a position to evaluate the dearomatization step. Unfortunately, all attempts to access the quinone epoxide 58 under classic or modified Adler-Becker reaction conditions failed. With these results, we closed the book on the second chapter in our vinigrol saga and went back to the drawing board. 

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