Which one of the following reagents is suitable for the converston of 2-cyclohexenone into 3-methylcyclohexanone ?

Options

A. `CH_(3)Mgl`
B. `(CH_(3))_(2)CuLi`
C. `CH_(3)I_(2)` and `Zn`
D. `CH_(3)AlCl_(2)`

Answer

To convert 2-cyclohexenone into 3-methylcyclohexanone, we need to analyze the structure of the starting material and the desired product, as well as the reagents that can facilitate this transformation.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **2-Cyclohexenone**: This compound has a double bond between carbon 2 and carbon 3, and a ketone functional group at carbon 1.
- **3-Methylcyclohexanone**: This compound has a methyl group attached to carbon 3 and a ketone at carbon 1.

2. **Understand the Reaction Type**:
- The conversion involves the addition of a methyl group to the double bond of 2-cyclohexenone. This indicates that we need a reagent that can add across the double bond without affecting the carbonyl group.

3. **Evaluate the Reagents**:
- **Option A: Grignard Reagent (e.g., CH3MgBr)**: This reagent would react with the carbonyl group rather than adding across the double bond. Thus, it is not suitable.
- **Option B: Gilman Reagent (e.g., CH3)2CuLi**: This reagent is known for its ability to add across double bonds without affecting carbonyl groups. Therefore, it is a suitable choice for this reaction.
- **Option C: Another Methyl Reagent**: Similar to the Grignard reagent, this would likely react with the carbonyl group, making it unsuitable.
- **Option D: Another Methyl Reagent**: Like option C, this would also react with the carbonyl group.

4. **Conclusion**:
- The only reagent that adds across the double bond without interfering with the carbonyl group is **Gilman’s reagent (Option B)**. Therefore, it is the most suitable reagent for converting 2-cyclohexenone into 3-methylcyclohexanone.

### Final Answer:
The suitable reagent for the conversion of 2-cyclohexenone into 3-methylcyclohexanone is **Option B: Gilman’s reagent (CH3)2CuLi**.