Show how Diels–Alder reactions might be used to synthesize the following compounds.
(c)
(d)

Verified step by step guidance

1. Step 1: Identify the target molecules (c) and (d) as products of Diels–Alder reactions. The Diels–Alder reaction involves a conjugated diene reacting with a dienophile to form a cyclic compound.
2. Step 2: For compound (c), analyze the structure. It contains a six-membered ring with two methyl groups and one ester group (-COOCH3). This suggests the diene should have two methyl substituents, and the dienophile should contain the ester group.
3. Step 3: Propose the diene for (c). A suitable diene would be 2,3-dimethyl-1,3-butadiene, as it has the two methyl groups in the correct positions to form the product.
4. Step 4: Propose the dienophile for (c). Methyl acrylate (CH2=CHCOOCH3) is a good choice because it contains the ester group (-COOCH3) that will be incorporated into the product.
5. Step 5: For compound (d), analyze the structure. It contains a bicyclic ring system with two ketone groups. This suggests the diene should be cyclic, and the dienophile should contain a carbonyl group. Cyclopentadiene can act as the diene, and maleic anhydride (C2H2(CO)2) can act as the dienophile to form the bicyclic product with two ketone groups.

Key Concepts

Diels–Alder Reaction

The Diels–Alder reaction is a [4+2] cycloaddition reaction between a conjugated diene and a dienophile, resulting in the formation of a six-membered ring. This reaction is a powerful tool in organic synthesis due to its ability to create complex cyclic structures in a single step, often with high stereoselectivity and regioselectivity.

Conjugated Dienes

Conjugated dienes are compounds that contain two double bonds separated by a single bond, allowing for resonance stabilization. This property enhances their reactivity in Diels–Alder reactions, as the electron-rich diene can effectively interact with an electron-deficient dienophile, facilitating the formation of new bonds.

Stereochemistry in Diels–Alder Reactions

Stereochemistry plays a crucial role in Diels–Alder reactions, as the orientation of substituents on the diene and dienophile can influence the final product's configuration. The reaction typically leads to the formation of two new stereocenters, and understanding the stereochemical outcomes is essential for predicting the structure of the synthesized compounds.