Enolate Chemistry

⚗️ Enolate Chemistry

Part 1 of 7 — Keto-Enol Tautomerism

1. Tautomers

keto and enol forms in equilibrium

2. Keto form is usually more stable

Keto form is usually more stable

3. Enolization catalyzed by acid or base

Enolization catalyzed by acid or base

4. α-hydrogens

H on carbon adjacent to carbonyl

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Key Concepts Summary

• Tautomers: keto and enol forms in equilibrium
• Keto form is usually more stable
• Enolization catalyzed by acid or base
• α-hydrogens: H on carbon adjacent to carbonyl

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Enolate Formation

Part 2 of 7 — Enolate Formation

1. Base removes α-hydrogen → enolate (resonance-stabilized carbanion)

Base removes α-hydrogen → enolate (resonance-stabilized carbanion)

2. LDA (lithium diisopropylamide)

strong, non-nucleophilic base

3. Kinetic vs thermodynamic enolate

Kinetic vs thermodynamic enolate

4. Enolates are nucleophilic at carbon

Enolates are nucleophilic at carbon

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Key Concepts Summary

• Base removes α-hydrogen → enolate (resonance-stabilized carbanion)
• LDA (lithium diisopropylamide): strong, non-nucleophilic base
• Kinetic vs thermodynamic enolate
• Enolates are nucleophilic at carbon

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Aldol Reaction

Part 3 of 7 — Aldol Reaction

1. Aldol reaction

enolate + carbonyl → β-hydroxy carbonyl

2. Aldol condensation

heat eliminates water → α,β-unsaturated carbonyl

3. Crossed aldol

two different carbonyls (use LDA for control)

4. Intramolecular aldol

forms 5- or 6-membered rings

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Key Concepts Summary

• Aldol reaction: enolate + carbonyl → β-hydroxy carbonyl
• Aldol condensation: heat eliminates water → α,β-unsaturated carbonyl
• Crossed aldol: two different carbonyls (use LDA for control)
• Intramolecular aldol: forms 5- or 6-membered rings

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Claisen Condensation

Part 4 of 7 — Claisen Condensation

1. Claisen condensation

ester enolate + ester → β-keto ester

2. Requires at least 2 α-hydrogens on starting ester

Requires at least 2 α-hydrogens on starting ester

3. Dieckmann cyclization

intramolecular Claisen

4. Decarboxylation of β-keto acids → ketones

Decarboxylation of β-keto acids → ketones

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Key Concepts Summary

• Claisen condensation: ester enolate + ester → β-keto ester
• Requires at least 2 α-hydrogens on starting ester
• Dieckmann cyclization: intramolecular Claisen
• Decarboxylation of β-keto acids → ketones

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Michael & Robinson Reactions

Part 5 of 7 — Michael & Robinson Reactions

1. Michael reaction

conjugate (1,4-) addition to enone

2. Michael donor (nucleophile) + Michael acceptor (enone)

Michael donor (nucleophile) + Michael acceptor (enone)

3. Robinson annulation

Michael + aldol cyclization → cyclohexenone

4. Powerful method for building six-membered rings

Powerful method for building six-membered rings

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Key Concepts Summary

• Michael reaction: conjugate (1,4-) addition to enone
• Michael donor (nucleophile) + Michael acceptor (enone)
• Robinson annulation: Michael + aldol cyclization → cyclohexenone
• Powerful method for building six-membered rings

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Problem-Solving Workshop

Part 6 of 7 — Problem-Solving Workshop

1. Predicting aldol and Claisen products

Predicting aldol and Claisen products

2. Designing enolate-based syntheses

Designing enolate-based syntheses

3. Analyzing crossed reactions for selectivity

Analyzing crossed reactions for selectivity

4. Retrosynthetic analysis of ring systems

Retrosynthetic analysis of ring systems

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Key Concepts Summary

• Predicting aldol and Claisen products
• Designing enolate-based syntheses
• Analyzing crossed reactions for selectivity
• Retrosynthetic analysis of ring systems

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Synthesis & Review

Part 7 of 7 — Synthesis & Review

1. Enolate chemistry builds C-C bonds

Enolate chemistry builds C-C bonds

2. Aldol and Claisen are the most important C-C forming reactions

Aldol and Claisen are the most important C-C forming reactions

3. Michael/Robinson extends to complex synthesis

Michael/Robinson extends to complex synthesis

4. Review

enolate reactions in synthesis

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Key Concepts Summary

• Enolate chemistry builds C-C bonds
• Aldol and Claisen are the most important C-C forming reactions
• Michael/Robinson extends to complex synthesis
• Review: enolate reactions in synthesis

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