Question

Predict the major product for each proposed Diels-Alder reaction. Include stereochemistry where appropriate.

a)

b)

c)

Short answer

a)

b)

c)

Step-by-step solution

Diels-Alder reaction

Diels-Alder reactions constitute reactions that are used to generate six-membered rings comprising controlled stereochemistry.These reactions are termed [4+2] cycloaddition reactions.

Stereochemistry requirements of the Diels-Alder reaction

The diene must comprise an s-cis conformation for the reaction to happen. In the final product the electron-withdrawing group is found in the stereochemical position near to the diene’s central atoms.

Predicting the products of the Diels-Alder reaction

(a)

In the reaction, the cyclopentadiene is the diene and the other compound is the dienophile. Cyclopentadiene is found in the cis-form in the Diels-Alder reaction. The NO₂ is the electron withdrawing group in the dienophile. It will occupy the endo position in the product. The stereochemistry and the reaction can be given as:

Major product of the Diels-Alder reaction in reaction a

(b)

In the following reaction, (Z)-3-methoxypenta-1,3-diene is a diene and benzoquinone is a deienophile. Due to syn addition, the substituents on the diene and dienophile present on the same side will be cis on the product. The electron-withdrawing group in the dienophile is the C=O group that will occupy the endo position.

The reaction along with the stereochemistry can be given as:

Major product of the Diels-Alder reaction in reaction b

(c)

In the following reaction, (1E, 3E)-1,4-diphenylbuta-1,3-diene is the diene and furan-2,5-dione is the dienophile. The electron-withdrawing group, C=O group occupy the endo position. The reaction and the stereochemistry can be given as:

Major product of the Diels-Alder reaction in reaction c