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V Addition of Carbanions to Activated Olefins
C
C
C
C
H
H+
H+
C
C
Z
C
C
C
Z
Z = COR, CO2R, CN, NO2 , etc.
Michael Addition ( Reaction)
Z
CH(CO2Et)2 + PhCH=CCO2Et
O-
O
PhCH CH
C OEt
PhCH CH
CH(CO2Et)2
B-
OEt
CH(CO2Et)2
CH3CHO + CH2(CO2Et)2
CH2(CO2Et)2
C
CH (C O2Et)2
CH 3CH
CH (C O2Et)2
CH3CH=C(CO2Et)2
O
O
CH2=CCO2Et t-BuOK
+
N
CO2Et
O
O
+
O
1. reflux
2.hydrolysis
1,5-dicarbonyl compounds
C
C
H
C
OH
O
1,4-addition
C
H
C
O
H
O
1,2-addition
Competitive pathway
O
Building of alicyclic system
O
CO 2Et
+
CO 2Et
O
EtO-
EtO2C
CO 2Et
O
O
1. hydrolysis
EtO-
2.
EtO2C
O
CO2
O
Dimedone
O
O
HCHO
H2O
O O
Dimedone
O
O
O
O
O
O
1. EtONa
O
2.
O
O
EtONa
H2O
O
Robinson cyclization
Harvard sterol synthesis
O
HCO2Et
EtO-
Me3CO-
O
O
CHO
OHH2O, HCO2H
O
CHO
O
O
VI. Condensation Involving Acetylides and Cyanide
R C
H
H+
CH
R C
H+
C N
C
C N
a) Alkylation
C
C
+
RX
X-
C
C
R
Functional transformation
C N
+ RX
X-
R
CN
Functional transformation
HC
CH
Na/NH3
Na/NH3
I (CH2)7Cl
NaCN
hydrolysis
partial
reduction
HC
C
CH3(CH2)7C
CH3(CH2)7Br
HC
C(CH2)7CH3
C(CH2)7CH2Cl
CH3(CH2)7C
C(CH2)7CH2CN
CH3(CH2)7C
C(CH2)7CH2CO2H
CH3(CH2)7C
C(CH2)7CH2CO2H
Oleic acid
HC
CH + 2HCHO
Cu+/NH3
CCH2OH
HOCH2C
reduction
oxidation
HOCH2CH2CH2CH2OH
HO2CCH2CH2CO2H
H+
heat
1. HBr
Succinic acid
O
Tetrahydrofuran
2. CN-
Na3PO4
heat
NC(CH2)4CN
hydrolysis
reduction
HO2C(CH2)4CO2H
H2N(CH2)6NH2
Adipic acid
CO
CH2=CHCH=CH2
Hexamethylenediamine
(CH2)4
CO
6.6-Nylon
NH(CH2)6NH
Butadiene
Aryl halides
PhBr
CuCN/Pyridine
200oC
PhCN
CN
Cl
NO2
NO2
CN-
NO2
NO2
b) Addition to Carbonyl Groups
(CH3)2CO + CH CH
1.
NH2-
2. H+
(CH3)2C
C
CH
OH
CH3
CH3COCH=CH2 + CH CH
NH2-
CH2=CH C C CH
OH
CH3
H+
rearrangement
CH2CH C C
OH
CH
O-
-
R2C=O CN
R2C
OH
HCN
R2C
CN
OH
+
H
H2O
CN
cyanohydrin
R2C
CO2H
 Hydoxyl acid
CH3
OH
(CH3)2 C
CN
H2SO4
CH3OH
CH2=CCO2CH3
esterfication and dehydration
Aromatic Aldehydes
CN-
2PhCHO
PhCOCHPh
OH
ArCH
H2O
ArCH
O-
CN
ArC
CN
CN
CN
CN
ArCH=O
Benzoin
H+
OH
ArCH=O
ArC
OH
CN
CHAr
OH O-
H2O
ArC
CHAr
OH OH
HCN
ArC
O
CHAr
OH
OH
C
OH
C
C N
OH
C
C N
C
N
c) Addition to Activated Olefins
PhCH=CHCOPh
HCN
PhCH
CH2COPh
CN
C8H17
C8H17
Et3Al HCN
CH3O2C
O
CH3O2C
O
CN
VII The Wittig Reaction
X
Ph3P +
CH
XPh3P
R
R1
Ph3P
C
R1
Ylide
R
CH
R
R1
Phosphonium salt
Ph3P
C
R1
Ylene
R
BuLi
+
Ph3P
CH R
Ph3P+ CHR
R1
+
2
C=O
O C
R
Ph3P
O
R2
R1
CHR
C
R1
RCH=C
+
R2
R2
The net result:
R1
Ph3P=O
H
C=O + Br C R1
R2
C
C R1
R2
Reactivity: aldehyde > ketone
Ylide:  position linking with an electron-withdrawing group
COR, CN, COOR, CHO
Ph3P
CH
C
O
R
Ph3P
CH
C
R
O-
Stabilizes the ylide and decreases its reactivity
Extremely stable, reacts with neither
ketones nor aldehydes
PPh3
The stereochemistry of the Wittig reaction
CH3
Ph
Ph3P=CHCH3 + PhCHO
C=C
H
H
cis ( Z )
H
Ph
Ph3P=CHCO2Et + PhCHO
C=C
H
CO2Et
trans ( E )
Conclusion: stable ylides give rise to stable olefins(E),
unstable ylides to unstable olefins(Z).
Applications of the Wittig reaction:
O + Ph3P=CH2
CH2
Exocylic double bond
-
Ph3P=CHCH2COO +
C=O
C=CHCH2CO2,-unsaturated acid
ROCH2Cl
PPh3
ROCH2PPh3Cl
R1
BuLi
R1
C O
R2
-
R1
hydrolysis
ROCH=C
R
Ph3PCH2CH2Br
ROCH=PPh3
2
base
HBr
C
R2
Ph3PCH=CH2
-elimination
CHO
An improvement of the Wittig reaction:
The Horner-Emmons reaction
(EtO)3P
(EtO)2P
RCH2X
+
O
base
(EtO)2P
CHR
C
O
C
CH2R
+
EtX
CHR + (EtO)2PO2-
O
Advantages of the reaction over the Wittig reaction:
1. Economy.
2. Higher reactivity.
3. Easiness to handle
The reactions of sulphur ylides
base
(CH3)2S+
CH2 S(CH3)2
R2C
(CH3)2SCH3IR2C
O-
CH2 R2CO
CH2 + CH3SCH3
O
Epoxy derivatives
(CH3)2SCH3I- base
O
R2C
O-
(CH3)2S+
CH2
R2CO
O
CH2 S(CH3)2
O
R2C
CH2 + CH3SCH3
O
O
The Mannich Reaction
O
O
HCHO
(CH3)2NH HCl
CH2N(CH3)2