Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.

Verified step by step guidance

1. Step 1: Understand the Dieckmann condensation reaction. The Dieckmann condensation is an intramolecular Claisen condensation where a diester reacts with a base to form a cyclic β-keto ester. This reaction typically forms 5- or 6-membered rings due to favorable ring strain considerations.
2. Step 2: Analyze each keto ester provided in the problem. Check the structure of each keto ester to determine if it can be formed by an intramolecular reaction that results in a 5- or 6-membered ring. Larger or smaller rings are generally not favored due to ring strain.
3. Step 3: For each keto ester that can form a 5- or 6-membered ring, identify the corresponding starting diester. The starting diester should have two ester groups positioned such that they can react intramolecularly to form the desired ring size.
4. Step 4: For keto esters that cannot form 5- or 6-membered rings, explain why they are not possible products of a Dieckmann condensation. This could be due to unfavorable ring strain or the inability to position the ester groups appropriately for the reaction.
5. Step 5: Draw the structures of the starting diesters for the keto esters that are possible products of the Dieckmann condensation. Ensure that the diester structures clearly show the ester groups in positions that allow for the formation of the desired cyclic β-keto ester.

Key Concepts

Dieckmann Condensation

Dieckmann condensation is a specific type of intramolecular aldol reaction that occurs between two ester groups in the presence of a strong base. This reaction typically leads to the formation of a β-keto ester. Understanding the mechanism involves recognizing how the base deprotonates the ester, allowing for nucleophilic attack on the carbonyl carbon of another ester group, ultimately forming a cyclic product.

Keto Esters

Keto esters are compounds that contain both a ketone and an ester functional group. They are characterized by the presence of a carbonyl group (C=O) adjacent to an ester group (RCOOR'). The formation of keto esters through Dieckmann condensation is significant in organic synthesis, as they can serve as intermediates for further reactions, including cyclization and functional group transformations.

Starting Diesters

Starting diesters are the initial compounds required for the Dieckmann condensation reaction. They must have two ester groups that are capable of undergoing intramolecular reaction. The structure and positioning of these ester groups are crucial, as they determine whether the condensation can occur and what type of cyclic product will be formed. Identifying the correct starting diesters is essential for predicting the possible keto esters that can result from the reaction.