Question

The correct option(s) of the reagents required for the following reaction is/are

• A. (i) Et₃B, O₂ (cat), THF; (ii) H₂O
• B. (i) Et₂CuLi, Me₃SiCl; (ii) H₃O⁺
• C. (i) EtMgBr, Et₂O; (ii) H₂O
• D. (i) "BuLi, THF; (ii) EtI

Answer 1

The Correct Option is A, B

The given reaction involves the conversion of a carbonyl compound into its ethyl-substituted derivative. To identify the correct reagents, let's examine the function of each given option:

1. The correct answer is (i) Et₃B, O₂ (cat), THF; (ii) H₂O and (i) Et₂CuLi, Me₃SiCl; (ii) H₃O⁺. Here's an explanation for each:
   • Et₃B, O₂ (cat), THF; (ii) H₂O: This reagent combination utilizes trialkylborane and catalytic oxygen in the presence of THF. The role of the trialkylborane is to participate in hydroboration, introducing an ethyl group into the molecule. Subsequent water addition facilitates the rearrangement to form the desired ethyl ketone.
   • Et₂CuLi, Me₃SiCl; (ii) H₃O⁺: This mixture involves a Gilman reagent (Et₂CuLi) that is capable of adding an ethyl group to the carbonyl. The Me₃SiCl is used to protect the resulting intermediate, and the acidic workup (H₃O⁺) regenerates the ketone.
2. The incorrect options:
   • (i) EtMgBr, Et₂O; (ii) H₂O: The Grignard reagent (EtMgBr) adds an ethyl group to carbonyls but leads to alcohol formation, not the desired ketone.
   • (i) "BuLi, THF; (ii) EtI: n-Butyllithium is a strong base and can lead to deprotonation rather than substitution, and ethyl iodide in the presence of a strong base can lead to side reactions, not delivering the desired product.

Hence, options (i) Et₃B, O₂ (cat), THF; (ii) H₂O and (i) Et₂CuLi, Me₃SiCl; (ii) H₃O⁺ are appropriate for this transformation of adding an ethyl group to the carbonyl compound to form an ethyl ketone.