Ester gives nucleophilic addition reaction followed by elimination reaction with carbon nucleopile. When carbon nucleophile is of an ester then the reaction is known as Claisen condensation reaction. This reaction is also carried out between ester and a ketone. A suC Cessful Claisen condensation requires an ester with two `alpha-` hydrogens and an equivalent amount of base rather than a catalytic amount of base.
Intramolecular Claisen condensation given diester is known as :

Options

A. Stobbe condensation
B. Dieckmann condesnation
C. Mannich reaction
D. Reformatsky reaction

Answer

To solve the question regarding the intramolecular Claisen condensation of a diester, we will follow these steps:

### Step-by-Step Solution:

**Step 1: Understand the Claisen Condensation Reaction**
- Claisen condensation is a reaction between esters (or an ester and a ketone) that involves nucleophilic addition followed by elimination. This reaction requires an ester with two alpha-hydrogens and a sufficient amount of base.

**Hint for Step 1:** Remember that Claisen condensation involves the formation of a carbon-carbon bond through nucleophilic attack.

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**Step 2: Identify Intramolecular Claisen Condensation**
- When the Claisen condensation occurs within a single molecule that contains two ester groups, it is referred to as intramolecular Claisen condensation. This leads to the formation of a cyclic compound.

**Hint for Step 2:** Focus on the term "intramolecular," which indicates that the reaction occurs within the same molecule.

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**Step 3: Recognize the Product of Intramolecular Claisen Condensation**
- The product of an intramolecular Claisen condensation of a diester is a beta-keto ester. This occurs after the elimination of an alcohol molecule.

**Hint for Step 3:** Beta-keto esters are characterized by having both a ketone and an ester functional group in the same molecule.

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**Step 4: Name the Reaction**
- The specific type of intramolecular Claisen condensation that occurs with a diester is known as "Dieckmann condensation."

**Hint for Step 4:** The name "Dieckmann" is associated with the intramolecular condensation of diesters to form cyclic compounds.

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**Final Answer:**
The intramolecular Claisen condensation of a diester is known as **Dieckmann condensation**.