Q64E
Question
The Stork enamine reaction and the intramolecular aldol reaction can be carried out in sequence to allow the synthesis of cyclohexanones. For example, the reaction of the pyrrolidine enamine of cyclohexanone with 3-buten-2-one, followed by enamine hydrolysis and base treatment, yields the product indicated. Write each step, and show the mechanism of each.
Step-by-Step Solution
VerifiedResonance-stabilized carbanions undergo 1,4-addition (or conjugate addition). The Michael Addition is thermodynamically regulated, with active methylenes like malonates and nitroalkanes as donors and activated olefins such, -unsaturated carbonyl compounds as acceptors.
Tautomerization is a net process during which protons are transported through one site to another within a sequence of stages, with the solvent serving as an intermediary.
The resultant intermediate is now very electrophilic, and water attacks the C=O carbon, resulting in an unstable tetrahedral intermediate. After that, nitrogen undergoes protonation, transforming it to a good leaving group that is ejected by the oxygen's lone pairs. After deprotonation of the oxonium ion, the respective ketone is produced.
One of the carbonyls is deprotonated at the -location and so acts as a nucleophile, attacking the other carbonyl's C=O carbon.