Question

Controlled alkylation of a ketone via an enamine intermediate is named as:

• A. Mannich reaction
• B. Robinson annulation
• C. Stork reaction
• D. Bamford Stevens reaction

Answer 1

The Correct Option is C

The reaction described in the question is the "Controlled alkylation of a ketone via an enamine intermediate," which is known as the Stork reaction. Let's explore the rationale behind this answer by considering what each option represents in organic chemistry.

1. Mannich Reaction: This involves the formation of a β-amino-carbonyl compound through the reaction of an amine, formaldehyde, and a carbonyl compound. It does not involve enamine intermediates.
2. Robinson Annulation: This is a useful method for synthesizing six-membered rings and involves the conjugate addition of a ketone to a cyclohexenone followed by an aldol condensation. It does not utilize an enamine intermediate.
3. Stork Reaction (Correct Answer): The Stork enamine reaction enables the alkylation of ketones which proceeds via the formation of an enamine intermediate. The enamine acts as a nucleophile, enabling alkylation to occur selectively at the position adjacent to the carbonyl group (α-position). This is the correct description of the process mentioned in the question.
4. Bamford Stevens Reaction: This involves the decomposition of tosylhydrazone derivatives to form alkenes, not through enamine intermediates.

The Stork reaction is uniquely characterized by the use of an enamine intermediate to facilitate the alkylation process, making it an essential tool in organic synthesis for introducing alkyl groups into molecules in a controlled manner.