Which of the following Diels`-` Alder reactions do not take place ?

Options

A.
B.
C.
D.

Explanation

To determine which of the following Diels-Alder reactions do not take place, we need to analyze the conditions required for a successful Diels-Alder reaction. The Diels-Alder reaction involves a diene and a dienophile, and there are specific criteria that must be met for the reaction to occur.

### Step-by-Step Solution:

1. **Understand the Diels-Alder Reaction**:
The Diels-Alder reaction is a cycloaddition reaction between a conjugated diene and a dienophile. For the reaction to occur, certain conditions must be met.

2. **Identify the Requirements**:
- The diene must be in the S-cis conformation. This means that the two double bonds of the diene should be on the same side, allowing for proper overlap with the dienophile.
- The diene should typically have electron-donating groups, while the dienophile should have electron-withdrawing groups to facilitate the reaction.
- The diene should not be linear; it should be able to adopt a non-linear conformation.

3. **Analyze Each Option**:
- **Option A**: If the diene is linear, it cannot adopt the required S-cis conformation, thus the reaction will not take place.
- **Option B**: If the diene has S-trans conformation, it cannot participate in the Diels-Alder reaction, as it does not have the necessary orientation for the reaction to occur.
- **Option C**: Similar to option B, if the diene is in S-trans conformation, the reaction will not take place.
- **Option D**: If the dienophile has electron-withdrawing groups instead of electron-donating groups, the reaction will not occur as the electronic requirements are not met.

4. **Conclusion**:
Based on the analysis, all options (A, B, C, and D) do not satisfy the conditions necessary for a Diels-Alder reaction to occur. Therefore, none of the reactions will take place.

### Final Answer:
The Diels-Alder reactions that do not take place are **A, B, C, and D**.

---