Summary
Claisen Reactions - Synthesis
O
Ph
O
OCH3
O
Ph
O
OCH3
/
H3C
CH3O–
O
O
OCH3
O
a β−ketoester
Ph
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What is the major product of this reaction?
CH
 A
OCH CH
 B
OH
O
OCH CH 1. CH CH O
A
 C
2. H O
CH
O
OCH CH
D
O
3
2
2
3
3
3
2
3
–
OCH2CH3
O
B
+
O
3
2
O
O
C
3
OCH2CH3
OH
D
Discussion Problems: Malonic Ester Synthesis
R–X
O
OH
O
H5C2O
H+ / H2O / Δ
C2H5O–
O
OC2H5
R–X
O
O
H5C2O
OC2H5
HO
H+ / H2O / Δ
C2H5O–
O
R–X
O
O
H5C2O
H+
C2H5O–
/ H2O / Δ
HO
OC2H5
Ph
O
R–X
O
H5C2O
O
O
C2H5O–
H+ / H2O / Δ
OC2H5
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OH
O
Discusion Problems: Acetoacetic Ester Synthesis
R–X
O
O
CH3
O
H+ / H2O / Δ
C2H5O–
OC2H5
R–X
O
O
CH3
OC2H5
H+ / H2O / Δ
C2H5O–
O
R–X
O
O
CH3
H+ / H2O / Δ
C2H5O–
OC2H5
O
R–X
O
CH3
O
C2H5O–
H+ / H2O / Δ
O
OC2H5
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O
Discussion Proglem:
Examples of Retrosynthesis
Retrosynthesis
aldol addition
Claisen condensation
ketone + ester condensation
Robinson annulation
malonic ester synthesis
acetoacetic ester synthesis
aldol condensation
OH O
O
O
OCH3
O
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Discussion Problems: More Retrosynthesis Examples
Retrosynthesis
aldol addition
Claisen condensation
ketone + ester condensation
Robinson annulation
malonic ester synthesis
acetoacetic ester synthesis
aldol condensation
O
O
O
HO
O
O
O
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Discussion Problems
(Predict the Products)
In these reactions the electrophile is in
excess to favor crossed product formation.
1) Condensation between a ketone and an ester
excess
2) Intramolecular Claisen condesation of a dicarboxylic ester