Single-step synthesis of Y via compatible reactants

Steps:

• Identify functional groups in compounds 1–4 and Y to match reaction requirements.
• Check for single-step reactions like nucleophilic addition or substitution that connect pairs to Y.
• Eliminate pairs requiring multi-step processes or incompatible groups.
• Verify B (1 and 4) forms Y directly via a standard reaction.

Why B is correct:

• Compounds 1 and 4 undergo Grignard addition, where the carbanion from 4 attacks the carbonyl in 1, yielding Y per the organometallic reaction mechanism.

Why the others are wrong:

• A: 1 and 3 require reduction after coupling, needing two steps.
• C: 2 and 3 form an elimination product, not Y.
• D: 2 and 4 lack a suitable electrophile-nucleophile pair for direct Y formation.

Final answer: B