Transcript Chapter 17. Aldehydes and Ketones

Aldehydes and Ketones carbonyl compounds
carbonyl group structure, bonding and physical properties
Review of methods of preparation of
aldehydes and ketones
hydration of alkynes
Friedel-Crafts acylation of aromatic
compounds
Overview of reactions of carbonyl
compounds
reduction to alcohols
addition of organometallic reagents
addition of oxygen, nitrogen, sulfur
and phosphorus nucleophiles
reduction of carbonyl to methylene
(Clemmensen or Wolff-Kishner)
Nucleophilic addition to carbonyls
Nucleophilic addition to carbonyls
Synthesis of Alcohols
Reduction of Carbonyl Compounds
Synthesis of Alcohols
Reduction of Carbonyl Compounds
Synthesis of Alcohols
Reduction of Carbonyl Compounds
H2/cat., NaBH4, LiAlH4
O
1. LiAlH4/ether
2. H2O
OH
lithium aluminum hydride (LAH)
O
+
Li AlH3
H
O
+
Li AlH3
H
Li +
-AlH3
O H
O
O
CH3CH2CCH2CH2COCH2CH3
1. LiAlH4/ether
2. H2O
CH3CH2CHCH2CH2CH2OH
OH
O
O
CH3CH2CCH2CH2COCH2CH3
NaBH 4/H2O
sodium borohydride
O
CH3CH2CHCH 2CH2COCH2CH3
OH
Synthesis of Alcohols Using Organometallic
Reagents
O
C
RMgX
+
O MgX
C
R
+
H3O
OH
C
R
O
C
RMgX
+
O MgX
C
R
O
C
MgX
R
+
H3O
OH
C
R
O
CH3(CH2)8CH2MgBr + HCH
1. ether
+
2. H O
3
CH3(CH2)8CH2CH2OH
O
COCH3 + 2 CH3MgBr
1. ether
+
2. H O
3
OH
CCH3
CH3
O
COCH3
CH3 MgBr
O
+MgBr
C OCH3
CH3
O
COCH3
O
+MgBr
C OCH3
CH3
CH3 MgBr
O
C CH3
-OCH
3
O
C CH3
CH3 MgBr
O
+MgBr
C CH3
CH3
O
C CH3
CH3 MgBr
O
+MgBr
C CH3
CH3
+
H
OH
CCH3
CH3
MgBr
+
O
1. THF
+
2. H3O
CH2CH2OH
Hydration of aldehydes and ketones
An example
Addition of alcohols: hemiacetal and
acetal formation
Addition of alcohols: hemiacetal and
acetal formation
O
+
+
ROH
OH
H3O
OR
hemiacetal
or hemiketal
Addition of alcohols: hemiacetal and
acetal formation
OH
+
+
OR
hemiacetal
ROH
OR
H3O
OR
acetal
Mechanism of acetal formation
O
+
H OH2
OH
+
+
O
R
O R
H
OH
R O
H
H
O+
R
Mechanism of acetal formation
+ R
R
O
O
R O
R
H
OR
+
H3O
+
OR
O+ H
H
O
H
An example
HO
O
+
HO
pTosOH
toluene
O
O
Addition of ammonia and amines:
imine and enamine formation
O
+
+
R
NH2
OH
H
R
NH
R
N
Examples
O
+
N
CH 3NH2
+
H3O
N CH
3
N
Examples
Examples
The Wittig Reaction
R
CH2X
+
Ph3P:
RCH2
PPh3
+
-
X
O
R
H
B:
RCH
PPh3
+
YLIDE
An example
The mechanism
Br
+
Ph3P:
PPh3
H
Br
Mechanism, cont.
PPh3
H
Br
PPh3 ylide
OH
Mechanism, cont.
PPh3
+
PPh3
O
O
oxaphosphetane
Mechanism, cont.
PPh3
O
Formation of cyanohydrins
O
1) CN
-
OH
+
2) H3O
C N
Example
Glc Glc O
H
C N
Reduction of carbonyls to alkanes
Clemmensen reduction
Wolff-Kishner reduction
Desulfurization of thioketals
Nucleophilic Addition to a,b-Unsaturated
Carbonyls
Nuc
+
Nuc
OH
O
Nuc OH
Nucleophilic Addition to a,b-Unsaturated
Carbonyls
Strong nucleophiles add 1,2
kinetic control
Weaker nucleophiles add 1,4
thermodynamic control
Nucleophilic Addition to a,b-Unsaturated
Carbonyls
O
KCN
H2O
Nucleophilic Addition to a,b-Unsaturated
Carbonyls
O
OH
KCN
H2O
NC
O
NC
Nucleophilic Addition to a,b-Unsaturated
Carbonyls
O
+ (CH 3CH 2)2CuLi
H2O
Et2O
Nucleophilic Addition to a,b-Unsaturated
Carbonyls
O
O
+ (CH3CH 2)2CuLi
H2O
Et2O
CH3CH2