Chapter 24, Problem 24.9P

Interpretation Introduction

Interpretation:

The product of the given Diels-Alder reaction is to be predicted, paying particular attention to the configuration of the $\text{C=C}$ double bond from the dienophile.

Concept introduction:

$\left[\text{4+2}\right]$ cycloaddition reactions are generally known as Diels-Alder reactions. A Diels-Alder reaction involves a diene and a dienophile. A diene shares four π electrons from the two conjugated π bonds while a dienophile shares two π electrons from a single π bond. The Diels-Alder reaction is concerted and proceeds through a six-membered aromatic transition state. For a Diels-Alder reaction to occur, the diene must be present in the s-cis conformation because both ends of the diene must be relatively close to the dienophile in the transition state. In a standard Diels-Alder reaction, four carbon atoms are rehybridized from ${\text{sp}}^{\text{2}}$ to ${\text{sp}}^{\text{3}}$, two from the dienophile and two from the diene. Due to this transformation, chiral centers may be introduced in the product. In a Diels-Alder reaction, the stereochemical configuration of the dienophile is preserved into the product. Thus Diels-Alder reactions are stereospecific because the stereochemistry of the product depends on the stereochemistry of the reactants. Since Diels-Alder reaction is concerted, it conserves the stereochemistry of the dienophile in the product.