Enols and enolates a substitutions and condensations of ketones and aldehydes
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Enols and Enolates a Substitutions and Condensations of Ketones and Aldehydes PowerPoint PPT Presentation


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Enols and Enolates a Substitutions and Condensations of Ketones and Aldehydes. Tautomerization Accelerated in Acid. a -Halogenation. Reaction Occurs via Enol. Tautomerization Acceleration in Base. Alkylation in Base Reaction with 1 o RX. Using LDA as Base to form Enolate.

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Enols and Enolates a Substitutions and Condensations of Ketones and Aldehydes

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Enols and Enolatesa Substitutions and Condensations of Ketones and Aldehydes


Tautomerization Accelerated in Acid


a-Halogenation


Reaction Occurs via Enol


Tautomerization Acceleration in Base


Alkylation in BaseReaction with 1o RX


Using LDA as Base to form Enolate


Alkylation a to C=OC-alkylation preferred


Alkylation Occurs on Less Hindered Side of C=O


Malonic Ester Synthesis of Carboxylic Acids


H’s are unusually acidic


Decarboxylation (loss of CO2)


2 Acidic a H’s, 2 Alkylations; Determine the Product of the Synthesis


All b-keto acids are unstable and Decarboxylate


Enamines can be Alkylated


Alkylation of an Enaminea Position is Activated


Complements LDA Reaction


LDA vs. Enamine Reaction


a-Selenation: Formation of a,b-Unsaturated Ketones


Mechanism


Synthesis


Aldol Condensation


Enolate Undergoes Nucleophilic Addition


Aldol CondensationDimerization of 3-Pentanone


Crossed Aldol Between 2 Different C=O Compounds


Four Possible Condensation Products


Crossed Aldol Condensation


Dehydration of Aldol Products


Predicting Aldol Dehydration Products


Intramolecular Aldol


Predict the Product


Conjugate Addition


1,2 - vs. 1,4 - Addition


Michael AdditionConjugate Addition of Enolate to a,b-Unsaturated Ketone


Robinson Annulation:Michael Addition followed by Aldol Consensation


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