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
The malonic ester synthesis
The acetoacetic ester synthesis
Direct alkylation of ketones, esters and nitriles
These compounds are MORE ACIDIC than CH3CH2OH (pKa = 16); NaOCH2CH3 can deprotonate them.
These compounds are SLIGHTLY LESS ACIDIC than CH3CH2OH;
NaOCH2CH3 would result in only a small amount of deprotonation.
These compounds are MUCH LESS ACIDIC than CH3CH2OH;
to deprotonate the top two, a base such as the R2N anion must be used.
A base removes a proton a to both carbonyl groups:
Resonance stabilizes the resulting anion:
The anion attacks the carbon bearing a leaving group:
A second equivalent of base can remove the second proton :
This anion can be alkylated by a second alkyl halide
a substituted malonic ester
a substituted acetic acid
a substituted acetoacetic ester
a substituted acetone
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