Lesson36 - The Claisen Condensation In this reaction, two...

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The Claisen Condensation In this reaction, two molar equiv of an ____ combine to produce a β -ketoester . One equiv serves as the nucleophile (enolate) and the other is the electrophile which undergoes addition and elimination. The reaction is driven to product by the final deprotonation step. ester + O CH 3 O EtO O O CH 3 O O CH 2 O H H O O CH 3 O a β -ketoester
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Mechanism of the Claisen Condensation + O CH 3 O EtO O O CH 3 O O CH 2 O O CH 2 O O O C CH 3 O OEt O CH 2 O O O CH 3 O H H H EtO a tetrahedral intermediate EtOH O CH 3 O EtO EtOH EtO [pt] [pt] [Ad N ] [E β ] an ester enolate pK a = 15.9 pK a = 10.7 The position of the equilibrium for the first three steps lies toward the starting ester. The overall reaction is driven to completion by the acid-base reaction between the ethoxide and β -ketoester.
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Mixed Claisen Condensation Like mixed aldol reactions, mixed Claisen condensations are useful if differences in reactivity exist between the two esters as for example when one of the esters has no α -hydrogen. Examples of such esters are: excess
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β -Ketoacids are Easily Decarboxylated
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Lesson36 - The Claisen Condensation In this reaction, two...

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