Question

For an unambiguous single step synthesis of the following target molecule (TM), the best bond disconnection in its retrosynthetic analysis is: 

• A.
• B.
• C.
• D.

Hint:

When analyzing Beta-keto esters in retrosynthesis, always consider the Claisen condensation pathway. The best disconnection is often at the bond between the Alpha-carbon and the carbonyl group, forming enolate and ester precursors.

Answer 1

The Correct Option is B

The target molecule (TM) is a β-keto diester, which can be synthesized in a single step via a Claisen condensation. In a Claisen condensation, an ester enolate reacts with another ester or a carbonyl compound to form a β-keto ester.

To apply this in retrosynthesis:

• Identify the position of the β-keto group and the two ester functionalities.
• The disconnection should occur between the \( \alpha \)-carbon of one ester and the carbonyl carbon of another ester.

In option (B), the disconnection leads to the formation of two plausible starting materials:

• Ethyl acetoacetate (a common β-keto ester)
• Diethyl carbonate or another ester to perform the Claisen condensation

This gives a clear, unambiguous, and synthetically accessible path in one step.

\[ \boxed{\text{Best disconnection: Option (B) via Claisen condensation}} \]