Acetoacetic ester synthesis

Acetoacetic ester synthesis
Reaction type	Coupling reaction
Reaction
	Acetoacetic acid esters
	+; R-X
	+; (-O-R & H3O+)
	↓
	α-substituted acetone
Conditions
Temperature	+Δ
Identifiers
Organic Chemistry Portal	acetoacetic-ester-synthesis
RSC ontology ID	RXNO:0000107

Acetoacetic ester synthesis is a chemical reaction where ethyl acetoacetate is alkylated at the α-carbon to both carbonyl groups and then converted into a ketone, or more specifically an α-substituted acetone. This is very similar to malonic ester synthesis.

Mechanism

A strong base deprotonates the dicarbonyl α-carbon. This carbon is preferred over the methyl carbon because the formed enolate is conjugated and thus resonance stabilized. The carbon then undergoes nucleophilic substitution. When heated with aqueous acid, the newly alkylated ester is hydrolyzed to a β-keto acid, which is decarboxylated to form a methyl ketone.^[1]^[2]

Double deprotonation of ethyl acetoacetate

The classical acetoacetatic ester synthesis utilizes the 1:1 conjugate base. Ethyl acetoacetate is however diprotic:^[3]

CH₃C(O)CH₂CO₂Et + NaH → CH₃C(O)CH(Na)CO₂Et + H₂

CH₃C(O)CH(Na)CO₂Et + BuLi → LiCH₂C(O)CH(Na)CO₂Et + BuH

The dianion (i.e., LiCH₂C(O)CH(Na)CO₂Et) adds electrophile to the terminal carbon as depicted in the following simplified form:^[3]

LiCH₂C(O)CH(Na)CO₂Et + RX → RCH₂C(O)CH(Na)CO₂Et + LiX

References

^ Smith, Janice Gorzynski. Organic Chemistry: Second Ed. 2008. pp 905–906
^ Acetoacetic Ester Synthesis – Alkylation of Enolates | PharmaXChange.info
^ ^a ^b Jin, Yinghua; Roberts, Frank G.; Coates, Robert M. (2007). "Stereoselective Isoprenoid Chain Extension with Acetoacetate Dianion: vary‐revision‐sha1, show‐toc CPU time usage: 0.309 seconds Real time usage: 0.384 seconds Preprocessor visited node count: 1426/1000000 Post‐expand include size: 22939/2097152 bytes Template argument size: 3486/2097152 bytes Highest expansion depth: 15/100 Expensive parser function count: 3/500 Unstrip recursion depth: 1/20 Unstrip post‐expand size: 5979/5000000 bytes Lua time usage: 0.145/10.000 seconds Lua memory usage: 2202471/52428800 bytes Number of Wikibase entities loaded: 0/400 -->

Zdroj:https://en.wikipedia.org?pojem=Acetoacetic_ester_synthesis
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Text je dostupný za podmienok Creative Commons Attribution/Share-Alike License 3.0 Unported; prípadne za ďalších podmienok.
Podrobnejšie informácie nájdete na stránke Podmienky použitia.

[1] Smith, Janice Gorzynski. Organic Chemistry: Second Ed. 2008. pp 905–906

[2] Acetoacetic Ester Synthesis – Alkylation of Enolates | PharmaXChange.info

[RmC-3] Jin, Yinghua; Roberts, Frank G.; Coates, Robert M. (2007). "Stereoselective Isoprenoid Chain Extension with Acetoacetate Dianion: vary‐revision‐sha1, show‐toc CPU time usage: 0.309 seconds Real time usage: 0.384 seconds Preprocessor visited node count: 1426/1000000 Post‐expand include size: 22939/2097152 bytes Template argument size: 3486/2097152 bytes Highest expansion depth: 15/100 Expensive parser function count: 3/500 Unstrip recursion depth: 1/20 Unstrip post‐expand size: 5979/5000000 bytes Lua time usage: 0.145/10.000 seconds Lua memory usage: 2202471/52428800 bytes Number of Wikibase entities loaded: 0/400 -->

[1]

[2]

[3]

Mechanism

Double deprotonation of ethyl acetoacetate

See also

References