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Examples: Aldehydes and ketones
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Conditions for Alpha Substitution
Add quickly
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Conditions for Carbonyl Condensations
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“Condensation” drives the overall reaction (notice equilibrium arrows)
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Synthesis: Two products can be formed by the aldol
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Symmetrical vs. Mixed Aldol
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Example: Single product mixed Aldol
No acidic protons
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Example: Single product mixed Aldol
These protons are more acidic, thus easier to remove
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Watch out for the possibility of mixture of products
In this case no mixture… why? – stability of pdt
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Example: Mixed Claisen
No acidic hydrogens
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Example: Mixed Claisen-“like”
A mixed aldol – Claisen type reaction
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Example: Intramolecular Claisen
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Intramolecular Claisen: Application to Synthesis
The β-keto ester formed still has one acid hydrogen and thus can do additional chemistry. Remember, the β-keto ester formed can be hydrolyzed to the β-keto acid and these can spontaneously decarboxylate.
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Review: Synthesis of an enamine
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Enamine’s react similar to enolates
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Example: Stork Reaction
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Example: Robinson Annulation
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Biological Claisen
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Glucose Biosynthesis (Gluconeogenesis)
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