Chapter 18, Problem 18.69P

Interpretation Introduction

(a)

Interpretation:

The synthesis of the given compound using the cyclopentanone as one of the reagents is to be suggested.

Concept introduction:

In aldol condensation, the aldehyde or ketone with $\text{α}$ hydrogen in the presence of a strong base like hydroxide or alkoxide produces $\text{β}$ hydroxyl carbonyl compound which in turn undergoes dehydration and forms $\text{α,β-}$ unsaturated carbonyl compound. The reaction proceeds with formation of enolate ion. The synthesis of $\text{α,β-}$ unsaturated carbonyl compound can be planned by retrosynthetic analysis. The precursor used in aldol condensation can be identified by disconnecting the double bond between $\text{α}$ and $\text{β}$ carbons. The bond disconnection is indicated by the wavy line.

Answer to Problem 18.69P

The synthesis of the given compound using cyclopentanone as one of the reagents is:

Explanation of Solution

The given compound is:

The given compound is a $\text{α,β-}$ unsaturated ketone, the double bond between $\text{α}$ and $\text{β}$ carbons is disconnected to arrive at the precursor used in its synthesis. As mentioned, one of the reagent used must be cyclopentanone. The retrosynthetic analysis is as follows:

The precursor determined is cyclopentanone. Two molecules of cyclopentanone are used in the aldol condensation. Cyclopentanone, on reaction with a strong base, forms the given $\text{α,β-}$ unsaturated ketone through the formation of $\text{β}$ hydroxyl carbonyl compound. The dehydration of $\text{β}$ hydroxyl carbonyl compound is carried out by heating, and can be represented as $\Delta$ on the reaction arrow. The synthesis planned is:

Conclusion

The synthesis of the given compound is planned by identifying the precursor used with disconnection of $\text{Cα}-\text{Cβ}$ bond.

Interpretation Introduction

(b)

Interpretation:

The synthesis of the given compound using cyclopentanone as one of the reagents is to be suggested.

Concept introduction:

In aldol condensation, the aldehyde or ketone with $\text{α}$ hydrogen in presence of a strong base like hydroxide or alkoxide produces $\text{β}$ hydroxyl carbonyl compound which in turn undergoes dehydration and forms $\text{α,β-}$ unsaturated carbonyl compound. In cross-aldol condensation, two different carbonyl compounds react where one carbonyl compound having $\text{α}$ hydrogen reacts with the base to form an enolate ion, which further adds to another carbonyl compound. The synthesis of $\text{α,β-}$ unsaturated carbonyl compound can be planned by retrosynthetic analysis. The precursor used in aldol condensation can be identified by disconnecting the double bond between $\text{α}$ and $\text{β}$ carbons. The bond disconnection is indicated by the wavy line.

Answer to Problem 18.69P

The synthesis of the given compound using cyclopentanone as one of the reagents is:

Explanation of Solution

The given compound is:

The given compound is $\text{α,β-}$ unsaturated ketone, the double bond between $\text{α}$ and $\text{β}$ carbon is disconnected to arrive at the precursor used in its synthesis. As mentioned, one of the reagents used must be cyclopentanone. The retrosynthetic analysis is as follows:

The precursors determined are cyclopentanone and benzaldehyde. As the benzaldehyde has no $\text{α}$ hydrogen, the enolate can be produced by the reaction of cyclopentanone with a strong base like hydroxide. The enolate on reaction with benzaldehyde produces the given $\text{α,β-}$ unsaturated ketone through the formation of $\text{β}$ hydroxyl carbonyl compound. The dehydration of $\text{β}$ hydroxyl carbonyl compound is carried out by heating, and can be represented as $\Delta$ on the reaction arrow. The synthesis planned is:

Conclusion

The synthesis of the given compound is planned by identifying the precursor used with disconnection of $\text{Cα}-\text{Cβ}$ bond.

Interpretation Introduction

(c)

Interpretation:

The synthesis of the given compound using cyclopentanone as one of the reagents is to be suggested.

Concept introduction:

In aldol condensation the aldehyde or ketone with $\text{α}$ hydrogen in presence of strong base like hydroxide or alkoxide produces $\text{β}$ hydroxyl carbonyl compound which in turn undergoes dehydration and forms $\text{α,β-}$ unsaturated carbonyl compound. In cross-aldol condensation, two different carbonyl compounds react where one carbonyl compound having $\text{α}$ hydrogen reacts with the base to form an enolate ion, which further adds to another carbonyl compound. The synthesis of $\text{α,β-}$ unsaturated carbonyl compound can be planned by retrosynthetic analysis. The precursor used in aldol condensation can be identified by disconnecting the double bond between $\text{α}$ and $\text{β}$ carbons. The bond disconnection is indicated by the wavy line.

Answer to Problem 18.69P

The synthesis of the given compound using cyclopentanone as one of the reagents is:

Explanation of Solution

The given compound is:

The given compound is $\text{α,β-}$ unsaturated ketone, the double bond between $\text{α}$ and $\text{β}$ carbon is disconnected to arrive at the precursor used in its synthesis. As mentioned, the one of the reagent used must be cyclopentanone. The retrosynthetic analysis is as follows:

The precursors determined are the cyclopentanone and acetophenone. As the both ketones has $\text{α}$ hydrogen, the enolate can be produced by the reaction of one of the ketone with a strong base like hydroxide. The enolate ion then reacts with another ketone and produces the given $\text{α,β-}$ unsaturated ketone through formation of $\text{β}$ hydroxyl carbonyl compound. The dehydration of $\text{β}$ hydroxyl carbonyl compound is carried out by heating, and can be represented as $\Delta$ on the reaction arrow. The synthesis planned is:

Conclusion

The synthesis of the given compound is planned by identifying the precursor used with disconnection of $\text{Cα}-\text{Cβ}$ bond.

Interpretation Introduction

(d)

Interpretation:

The synthesis of the given compound using cyclopentanone as one of the reagents is to be suggested.

Concept introduction:

In aldol condensation the aldehyde or ketone with $\text{α}$ hydrogen in presence of strong base like hydroxide or alkoxide produces $\text{β}$ hydroxyl carbonyl compound which intern undergoes dehydration and forms $\text{α,β-}$ unsaturated carbonyl compound.

Instead of carbonyl compounds, the compounds with polar $\text{π}$ bond having $\text{α}$ hydrogen like nitrile can also be used in aldol condensation, which can form a nucleophile like enolate ion on deprotonation. The synthesis of $\text{α,β-}$ unsaturated nitrile can be planned by retrosynthetic analysis. The precursor used in aldol condensation can be identified by disconnecting the double bond between $\text{α}$ and $\text{β}$ carbons. The bond disconnection is indicated by the wavy line.

Answer to Problem 18.69P

The synthesis of the given compound using cyclopentanone as one of the reagents is:

Explanation of Solution

The given compound is:

The given compound is $\text{α,β-}$ unsaturated nitrile, the double bond between $\text{α}$ and $\text{β}$ carbons is disconnected to arrive at the precursor used in its synthesis. As mentioned, one of the reagent used must be cyclopentanone. The retrosynthetic analysis is as follows:

The precursors determined are cyclopentanone and nitrile compound. As the nucleophile adds to carbonyl, the nucleophile can be produced by the reaction of one of the nitrile with a strong base like hydroxide. The nucleophile then reacts with ketone and produces the given $\text{α,β-}$ unsaturated nitrile through the formation of $\text{β}$ hydroxyl nitrile compound. The dehydration of $\text{β}$ hydroxyl nitrile compound is carried out by heating, can be represented as $\Delta$ on the reaction arrow. The synthesis planned is:

Conclusion

The synthesis of the given compound is planned by identifying the precursor used with disconnection of $\text{Cα}-\text{Cβ}$ bond.

Interpretation Introduction

(e)

Interpretation:

The synthesis of the given compound using cyclopentanone as one of the reagents is to be suggested.

Concept introduction:

The Robinson annulations reaction is the addition of enolate to conjugated carbonyl followed by intramolecular aldol condensation. One of the reactant in Robinson annulations must be $\text{α,β-}$ unsaturated carbonyl with at least two $\text{α}$ hydrogens and another must be simple aldehyde or ketone having $\text{α}$ hydrogen. The simple aldehyde or ketone first reacts with strong base to form enolate ion, which undergo $\text{1, 4-}$ addition across the conjugated carbonyl. The product formed is then undergo intramolecular adol condensation and forms a product forming new six membered ring with $\text{α,β-}$ unsaturated carbonyl functional group. The synthesis of $\text{α,β-}$ unsaturated nitrile can be planned by retrosynthetic analysis. The precursor used in aldol condensation can be identified by disconnecting the double bond between $\text{α}$ and $\text{β}$ carbons. The bond disconnection is indicated by the wavy line.

Answer to Problem 18.69P

The synthesis of given compound using cyclopentanone as one of the reagents is:

Explanation of Solution

The given compound is:

The given compound is $\text{α,β-}$ unsaturated ketone with six membered fused ring system; the double bond between $\text{α}$ and $\text{β}$ carbon is disconnected to arrive at the intermediate product.

To get the precursor $\text{α,β-}$ unsaturated carbonyl, disconnect the bond between $\text{β}$ and $\text{γ}$ carbons, then place the double bond between $\text{α}$ and $\text{β}$ carbons and form a carbonyl at $\text{γ}$ carbon. As mentioned, one of the reagent used must be cyclopentanone. The retrosynthetic analysis is as follows:

The precursors determined are the cyclopentanone and $\text{α,β-}$ unsaturated ketone. As the enolate adds to conugated carbonyl, the enolate can be produced by the reaction of cyclopentanone with a strong base like hydroxide. The enolate then reacts with $\text{α,β-}$ unsaturated ketone and forms $\text{1, 6-dione}$. The $\text{1, 6-dione}$ then undergoes intramolecular aldol condensation and forms the $\text{β}$ hydroxyl ketone with the fused six membered ring compound. Thus is further on dehydration by heating produces desired product. The heat is represented as $\Delta$ on reaction arrow. The synthesis planned is:

Conclusion

The synthesis of given compound is planned by identifying the precursor used with disconnection of $\text{Cα}-\text{Cβ}$ bond.