Question

The major product formed in the following reaction sequence is 

• A. A
• B. B
• C. C
• D. D

Hint:

In multi-step organic synthesis questions, track each reagent’s role:
- NaOEt/diethyl malonate → Knoevenagel condensation
- (CH$_3$)$_2$NH → Michael addition
- LiAlH$_4$ → reduction
- BF$_3$/HCHO → methylation (Eschweiler–Clarke).

Answer 1

The Correct Option is B

Step 1: Knoevenagel condensation.
2-Formylpyridine reacts with diethyl malonate in the presence of NaOEt to form an $\alpha,\beta$-unsaturated ester via the Knoevenagel condensation mechanism. \[ \text{Pyridine-CHO} + (\text{EtOOC–CH}_2\text{–COOEt}) \rightarrow \text{Pyridine–CH=CH–COOEt} \] Step 2: Michael addition.
The resulting conjugated ester undergoes 1,4-addition with dimethylamine (CH$_3$)$_2$NH, leading to a $\beta$-dimethylamino ester intermediate.
Step 3: Reduction.
Reduction with LiAlH$_4$ converts the ester to a primary alcohol, giving a $\beta$-amino alcohol.
Step 4: Eschweiler–Clarke methylation.
Finally, treatment with BF$_3$ and formaldehyde (HCHO) methylates the secondary amine to a tertiary amine, producing a **tertiary amino diol**.
Step 5: Product formed.
The final product is 2-(2-(dimethylamino)-1-hydroxyethyl)pyridin-1-ol, corresponding to **Option (C)**.
Step 6: Conclusion.
Hence, the correct answer is (C).