Chapter 27, Problem 27.40P

Interpretation Introduction

(a)

Interpretation: The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are to be predicted.

Concept introduction: A chemical reaction that involves $\left[4+2\right]$ cycloaddition is called Diels-Alder reaction. The reactant molecules that give rise to the product are diene and dienophile. The rate of reaction is fast when the electronegative group is attached to dienophile. In this type of reaction, syn addition takes place.

Answer to Problem 27.40P

The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and $\text{dimethyl}\text{but}-2-\text{ynedioate}$.

Explanation of Solution

The given product is shown below.

Figure 1

Retro synthesis can be carried out to identify the diene and dienophile for the given product.

The reaction that shows the disconnection approach of the given product is shown below.

Figure 2

In the given product, the ring is opened due to the rearrangement of $\text{π}$ bonds as shown in the above diagram. This results in the formation of diene and dienophile. Therefore, the starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and $\text{dimethyl}\text{but}-2-\text{ynedioate}$.

Conclusion

The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and $\text{dimethyl}\text{but}-2-\text{ynedioate}$.

Interpretation Introduction

(b)

Interpretation: The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are to be predicted.

Concept introduction: A chemical reaction that involves $\left[4+2\right]$ cycloaddition is called Diels-Alder reaction. The reactant molecules that give rise to the product are diene and dienophile. The rate of reaction is fast when the electronegative group is attached to dienophile. In this type of reaction, syn addition takes place.

Answer to Problem 27.40P

The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and dimethyl maleate.

Explanation of Solution

The given product is shown below.

Figure 3

Retro synthesis can be carried out to identify the diene and dienophile for the given product.

The reaction that shows the disconnection approach of the given product is shown below.

Figure 4

In the given product, the ring is opened due to the rearrangement of $\text{π}$ bonds as shown in the above diagram. This results in the formation of diene and dienophile. The above diagram shows that the substituents $\left({\text{COOCH}}_{\text{3}}\right)$ attached to the dienophile are on same sides. Therefore, both the substituents are present on the same side of the product as well.

Thus, the starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and dimethyl maleate.

Conclusion

The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and dimethyl maleate.

Interpretation Introduction

(c)

Interpretation: The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are to be predicted.

Concept introduction: A chemical reaction that involves $\left[4+2\right]$ cycloaddition is called Diels-Alder reaction. The reactant molecules that give rise to the product are diene and dienophile. The rate of reaction is fast when the electronegative group is attached to dienophile. In this type of reaction, syn addition takes place.

Answer to Problem 27.40P

The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and dimethyl maleate.

Explanation of Solution

The given product is shown below.

Figure 5

Retro synthesis can be carried out to identify the diene and dienophile for the given product.

The reaction that shows the disconnection approach of the given product is shown below.

Figure 6

In the given product, the ring is opened due to the rearrangement of $\text{π}$ bonds as shown in the above diagram. This results in the formation of diene and dienophile. The above diagram shows that the substituents $\left({\text{COOCH}}_{\text{3}}\right)$ attached to the dienophile are on opposite sides. Therefore, both the substituents are present on the opposite side of the product as well.

Thus, the starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and dimethyl maleate.

Conclusion

The starting materials that are needed to synthesize the given compound by a thermal $\left[4+2\right]$ cycloaddition are $\text{octa}-3,5-\text{diene}$ and dimethyl maleate.