Diels Alder Reactions

In the past few weeks of class we have been learning about a reaction called the Diels Alder reaction. A Diels Alder reaction is an organic chemical reaction between a conjugated diene and a substituted alkene. The substituted alkene is commonly known as a dienophile. When these two react, a cyclohexene will always form. Otto Paul Hermann Diels and Kurt Alder first described this reaction in 1928. This reaction occurs via a single cyclic transition state. No intermediates occur during the reaction. As concerted cycloadditions, these reactions are stereospecific.  A simple Diels-Alder reaction can be seen in the following video below (1).

https://www.youtube.com/watch?v=_4gQktVXpgU

            These Diels-Alder reactions can be seen in nature. One example that was found in research done by Princeton University was Solanapyrone A. As stated in the research, Solanapyrone A is “ a decalin polyketide phytotoxin produced by the pathogenic fungus Alternaria solani, causal organism of potato early blight disease.” This is an intermolecular reaction that resulted with a 2:1 ratio of the endo product to the exo product (2). This reaction can be seen below.

http://www.princeton.edu/~orggroup/supergroup_pdf/da_ase_lowres.pdf

            Overall, Diels-Alder reactions are a reaction between a diene and a dieneophile. These reactions also result in a cyclohexene with no intermediates during the process. Solanapyrone A helps to show that these reactions surround us in nature. For more information on Diels-Alder reactions check out chapter 16 in the text book Organic Chemistry 3^rd edition by Janice Gorzynski Smith. 

References:

1.     The diels-alder cycloaddition. (n.d.). Retrieved from

http://chemwiki.ucdavis.edu/Organic_Chemistry/Conjugation/The_Diels-

Alder_Cycloaddition

2.     Drhal, C. (2005). Evidence for enzymatic catalysis of the diels-alder reaction in

nature. In Organic Supergroup LiteratureRetrieved from

http://www.princeton.edu/~orggroup/supergroup_pdf/da_ase_lowres.pdf