Question

The reaction that produces the following as a major product is 

• A. A
• B. B
• C. C
• D. D

Hint:

The Wittig reaction is used to convert aldehydes or ketones into alkenes by reaction with phosphonium ylides (Ph$_3$P=CHR) in the presence of a base such as t-BuOK.

Answer 1

The Correct Option is B

Step 1: Identify the product type.
The product is an $\alpha,\beta$-unsaturated ether, indicating the formation of a C=C bond through a carbonyl olefination reaction.
Such products are typically formed via the Wittig reaction.
Step 2: Recall the Wittig reaction.
In the Wittig reaction, an aldehyde or ketone reacts with a phosphonium ylide (Ph$_3$P=CHR) to form an alkene.
The reaction is base-promoted (using t-BuOK, NaH, or similar) and proceeds through a betaine intermediate and oxaphosphetane transition state.
\[ \text{R–CHO} + \text{Ph}_3\text{P=CH–R'} \xrightarrow{\text{t-BuOK}} \text{R–CH=CH–R'} + \text{Ph}_3\text{P=O} \] Step 3: Apply to given reactants.
Aldehyde: CH$_3$OCH$_2$CHO
Ylide: Ph$_3$P=CH–CH(CH$_3$)CH$_3$
The reaction forms the alkene: \[ \text{CH}_3\text{OCH}_2\text{CH=CHCH(CH}_3\text{)CH}_3 \] which matches the product given.
Step 4: Eliminate other options.
(B) Involves reductive acylation (not olefination).
(C) Lindlar’s catalyst partially reduces alkynes, not forming new C=C bonds here.
(D) Involves oxidation, not C=C bond formation.
Step 5: Conclusion.
Hence, the product is formed via the Wittig reaction, as in Option (A).