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NucleophilicAdditionOfHardAnionsToAldehydesAndKetonesfrom chapter(s) _______ in the recommended text
A. Introduction
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B. Types Of Additions To Carbonyls PolarityOfCarbonyls. positively polarized. to carbonyl carbons oxygen. ReactivityOfNucleophilesAndCarbonylsAtDifferentpHValues
more reactive more reactive than ones that are not. hard because are likely to cannot be used completely wrong to show neutral or basic conditions. cannot be reversible.
CH3- NH3O O+H
O
A
drawarrowhere
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FormationOfTetrahedralIntermediates
sp3 hybridized. give alcohols. (this is kinetics), (thermodynamics).
tetrahedral intermediate
O-OEt
H
-O OEt
tetrahedral intermediate
O-H
H
-O H
tetrahedral intermediate
O-CH3
H
-O CH3
tetrahedral intermediate
O-
H
-O
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one C–O bond(s) one bond(s) the starting materials. it will be ie irreversible addition.
reversibly to ketones
C. Reactions of Aldehydes And Ketones With Hydridic Reducing Agents
relatively stable relatively unstable
MeO-Cl- Br- CN- Me- Ph- CH2CH-
tetrahedral intermediate
OH-
H+
product
H
-O HH
HO H
O
PhH-
H+
Ph H
-O HPh
OH
OH-
H+
H
-O H OH
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does not do
OH-
H+-O H OH
O
H-H+-O H OH
NaBH4 NaH LiAlH4
nucleophilc basic nucleophilc
name: Sodium Borohydride Sodium Hydride Lithium Aluminium Hydride
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reduction processes.
O
NaBH4 H2O
-O H OH
two diastereomers
O
(i) NaBH4
(ii) H++
OH OH
O
(i) LiAlH4
(ii) H+OH
O (i) NaBD4
(ii) H++
two diastereomers
H
HO DH
D OH
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because:
Lithium aluminium hydride can reduce ester to alcohol, but sodium borohydride cannot.
OH O
OH O
OHOH OHO
MeO2COH
MeO2CO
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D. Addition Of Carbanions reactive carbonyls irreversibly. is stronger than under anhydrous conditions. alkoxide does not
OH OH
H
OHOH
OHCN CCl3
EtHO OOH
OHOH OH
OH OH
OH
OHOH
OMe-
tetrahedral intermediate
H+-O Me HO Me
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O Et-
tetrahedral intermediate
H+-O Et HO Et
O
tetrahedral intermediate
H+-
H
-O PhPh
OH
O
tetrahedral intermediate
H+Ph-
H
-O PhPh
OH
O
tetrahedral intermediate
H+-
H
-O HO H
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O
tetrahedral intermediate
H+Ph- -O Ph HO Ph
O
tetrahedral intermediate
H+Et-
H
-O EtEt
OH
O
tetrahedral intermediate
H+O-H
-O OOH
O
O Et-
tetrahedral intermediate
H+-O Et HO Et
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E. Reactions Of Carbonyl Compounds With Acetylide Anions NEt3 NaNH2 MeMgBr HO- LiNiPr2 LiBu Na2CO3
secondary or tertiary
Ph
O Li Ph H3O+
Ph
O-Li
PhPh
OH
Ph
OLi(i)
(ii) H+HO
H2CO(i) H2C2, excess NaH
(ii) H+
OH
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EtO (ii) H+
two diastereomers
+Li(i)
EtOH
EtOH
OH O
OH HO O
Ph
OH
Ph
O
Ph
two diastereomers
OH OH OO
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F. Si And Re Faces Revisited enantiomers. Re-face attack Si -face attack.
OHO
OO
Ph
OEt-
Re-faceaddition
Si-faceaddition
Et-
PhHO Et
PhEt OH
LiAlH4O
Re-face
OH
Me-
Si-face
O OHMe