Question

Question: Draw the product of each Diels–Alder reaction and indicate the stereochemistry at all stereogenic centers

Short answer

Answer

The cyclic product of the reaction (a)

The cyclic product of the reaction (b)

Step-by-step solution

Diels-Alder reaction

The [4+2] cycloaddition of conjugated diene (diene) and an alkene with an electron-withdrawing group (dienophile) under thermal conditions to give a cyclohexene derivative is known as the Diels-Alder reaction.

Diels–Alder reaction conditions and product

• In the reaction, (2E,4E)-hexa-2,4-diene is the diene, and furan-2,5-dione is the dienophile.

For the Diels-Alder reaction condition,

• s-trans diene should be converted to s-cis form.

• Due to syn addition, the substituents on diene and dienophile, which are on the same side, will be ‘cis’ in the product.

• According to the endo rule, the dienophile C=O will occupy the endo position.

• Because of suprafacial addition, the stereochemistry is retained in the product.

Therefore,

The cyclic product of the reaction (a) can be shown as:

The cyclic product of the reaction (b) can be shown as:

Methyl groups are ‘trans’ to each other