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Alkylation of Enolate Ions. The malonic ester synthesis The acetoacetic ester synthesis Direct alkylation of ketones, esters and nitriles. Relative acidity of selected organics. Structure pKa 5 9 11 13

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alkylation of enolate ions

Alkylation of Enolate Ions

The malonic ester synthesis

The acetoacetic ester synthesis

Direct alkylation of ketones, esters and nitriles

relative acidity of selected organics
Relative acidity of selected organics

StructurepKa

5

9

11

13

These compounds are MORE ACIDIC than CH3CH2OH (pKa = 16); NaOCH2CH3 can deprotonate them.

relative acidity of selected organics3
Relative acidity of selected organics

StructurepKa

16

17

19

These compounds are SLIGHTLY LESS ACIDIC than CH3CH2OH;

NaOCH2CH3 would result in only a small amount of deprotonation.

relative acidity of selected organics4
Relative acidity of selected organics

StructurepKa

25

25

35

40

These compounds are MUCH LESS ACIDIC than CH3CH2OH;

to deprotonate the top two, a base such as the R2N anion must be used.

acidity of b dicarbonyl compounds
Acidity of b-dicarbonyl compounds

A base removes a proton a to both carbonyl groups:

Resonance stabilizes the resulting anion:

general mechanism for alkylation
General mechanism for alkylation

The anion attacks the carbon bearing a leaving group:

A second equivalent of base can remove the second proton :

introduction of a second alkyl group
Introduction of a second alkyl group:

This anion can be alkylated by a second alkyl halide

hydrolysis and decarboxylation
Hydrolysis and Decarboxylation

a substituted malonic ester

a substituted acetic acid

hydrolysis and decarboxylation9
Hydrolysis and Decarboxylation

a substituted acetoacetic ester

a substituted acetone

forming a ring that includes the a carbon
Forming a ring that includes the a-carbon

Substituted acetic acids having a ring that includes the a-carbon

can be synthesized similarly using diethyl malonate:

5- or 6-membered rings can be made using a 4- or 5-carbon alkyl dihalide