Diels–Alder reaction

1. Diels–Alder reaction Prepared by : MalakEshtayah

2. The Contents : Objectives Background information The reaction mechanism Applications and recent literature Conclusion References The End

3. Objectives : • I make this show in order to achieve the followings : • Give a brief information about Diels-Alder reaction which I hope it will satisfied your curiosity about it. • Show you the reaction mechanism. • Give you some application where you can use this reaction. • Show you some information about recent literature about this reaction.

4. Background information: • This reaction is named after Otto Paul Hermann Diels & Kurt Alder. • Otto Paul Hermann Diels and Kurt Alder first documented the novel reaction in 1928 for which they were awarded the Nobel Prize in Chemistry in 1950 for their work on the eponymous reaction. • The Diels-Alder reaction is a member of a class of reactions called cycloadditions. In all Diels-Alder reactions, three π bonds, two in a diene and one in a dienophile, reorganize to give a six-membered ring containing one π bond and two new sigma bonds.

5. Background information : • The Diels–Alder reaction is generally considered the "Mona Lisa" of reactions in organic chemistry since it requires very little energy to create a cyclohexene ring, which is useful in many other organic reactions. • DA reactions are reversible and in a retro-Diels–Alder reaction the diene and alkene are reformed. • A variant is the hetero-Diels-Alder, in which either the diene or the dienophile contains a heteroatom, most often nitrogen or oxygen. This alternative constitutes a powerful synthesis of six-membered ring heterocycles.

6. Background information : • Some terminology related to the Diels-Alder reaction: A concerted reaction is one in which all of the electrons move at the same time. The Diels-Alder reaction is a concerted reaction. Other examples: SN2 and E2 reactions are concerted. In contrast, SN1 and E1 reactions are not, because they involve the formation of an intermediate (a carbocation).

7. The reaction mechanism : • That is, the three π bonds of the reactants move to give two sigma bonds and a π bond in the cyclohexene ring of the product. Any group attached to the six carbons of the three rings is carried along for the ride. Diene dienophile Cyclohexene

8. The reaction mechanism : • Common dienophiles that are used are –C=C-Z or Z-C=C-Z’, where Z and Z’ may be CHO, COR, COOH, COOR, COCl, COAr, CN, NO2, Ar, CH2Cl, CH2NH2, CH2CN, CH2COOH, halogen or C=C. •  Nearly all conjugated dienes will react with appropriate dienophiles. By varying the type of diene and dienophiles, many different types of ring structures can be synthesized.Addition is syn on both components (bonds form from same species at the same time).

9. The reaction mechanism : (Stereochemistry) • The cis principle applies to the Diels-Alder reaction (with very, very few exceptions). Here is an example of the stereochemistry of the reactants being conserved in the products. •             The major product of a cyclic diene Diels-Alder reaction is an endo addition, which means that the electron withdrawing group(s) will be on the same side as the double bond of a bicyclic ring, as shown here: A B A B H D H D

10. Applications and recent literature: • Some the most important applications that D-A reaction was used is the synthesis of natural products. • Recent Literature: • ChiralOxazaborolidine-Aluminum Bromide Complexes Are Unusually Powerful and Effective Catalysts for Enantioselective Diels-Alder ReactionsD. Liu, E. Canales, E. J. Corey, J. Am. Chem. Soc., 2007, 129, 1498-1499.

11. Applications and recent literature: Regioselective and Asymmetric Diels-Alder Reaction of 1- and 2-Substituted Cyclopentadienes Catalyzed by a Brønsted Acid Activated ChiralOxazaborolidineJ. N. Payette, H. Yamamoto, J. Am. Chem. Soc., 2007, 129, 9536-9537. DiarylprolinolSilyl Ether as Catalyst of an exo-Selective, Enantioselective Diels-Alder ReactionH. Gotoh, Y. Hayashi, Org. Lett., 2007, 9, 2859-2862.

12. Conclusions: • The Diels-Alder reaction is a conjugate addition reaction of a conjugated diene to an alkene (the dienophile) to produce a cyclohexene. • Due to the high degree of regio- and stereoselectivity (due to the concerted mechanism), the Diels-Alder reaction is a very powerful reaction and is widely used in synthetic organic chemistry. • The reaction usually thermodynamically favourable due to the conversion of 2 π-bonds into 2 new stronger σ-bonds. • Normal Diels-Alder reaction is favoured by electron withdrawing groups on the electrophilicdienophile and by electron donating groups on the nucleophilicdiene. • The Diels-Alder reaction is stereospecific with respect to both the diene and the dienophile.

13. References : • The Diels–Alder Reaction in Total SynthesisK. C. Nicolaou, S. A. Snyder, T. Montagnon, G. VassilikogiannakisAngew. Chem. Int. Ed.2002, 41, 1668–1698. (Review) doi:10.1002/1521-3773(20020517)41:10<1668::AID-ANIE1668>3.0.CO;2-Z • Kozmin, S. A.; He, S.; Rawal, V. H. Organic Syntheses, Coll. Vol. 10, p.442 (2004); Vol. 78, p.160 (2002). (Article) • Pham, P.-T.; Vince, R. Phosphorus, Sulphur and Silicon2007, 779–791. • Applied Organometallic Chemistry . Volume 9,Issue 3,pages 163–174, May 1995. • Surrey, Alexander R. Name Reactions in Organic Chemistry 2nd Edition.  Academic    Press INC.  New York, 1961.

14. The End • Thank you for your patient … and your attention … I hope I satisfied your curiosity … and achieved what I was looking for … • With all my respect and gratefulness to my Doctor and for you my friends …