CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Chromium based oxidation
1
R OH R CHO
OH
R R'
O
R R'
R OH R COOH
Transformation Chromium reagent PCC, Collins reagent, PDC in DCM
PCC, Collins reagent, PDC, Jones reagent
Jones reagent, PDC in DMF
CHO
Etard reaction
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation KMnO4 MnO2 Mn(OAc)3
Potassium permanganate (KMnO4)
R'
RKMnO4+
R'
R OMnO O
O-K+
R'
R OH
OH
HOMn
HO O
O-K++
R'
R OMnO O
O-K+H
R'
R O
OH R'
R O
O
Under mild condition KMnO4 can effect conversion of alkenes to glycol
KmnO4 is such a powerful oxidant that it can cleave the glycol further. So, careful control is required
2
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
R R'KMnO4, H2O
Manganese based oxidation
R R'
HO OH
R
R'O
O
R R'
O OH
ArKMnO4, H2O ArCO2H
CH3Ar KMnO4, H2OArCO2H
Potassium permanganate (KMnO4)
In water medium:
3
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation Potassium permanganate (KMnO4)
In Organic Solvents:
3.3 mol KMnO4
Benzene polyether
1.0 mol KMnO4
R4NCl
OH
OH
O
O
Oxidation of acetylenes:
Ph CH2CH2CH3
KMnO4
R4N+, DCM HO
CH2CH2CH3
OH
Ph
O
CH2CH2CH3
OH
Ph
O
CH2CH2CH3
O
Ph
4
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation Potassium permanganate (KMnO4)
Oxidation of aromatic side chain:
Ar R Ar CO2HKMnO4
R3C NH2 R3C NO2KMnO4
Oxidation of amino compounds:
Tertiary alkylamines can be oxidized to nitro compounds
Oxidation of sulphides:
S
NO2
O2N S
NO2
O2NO
O
KMnO4
5
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation Potassium permanganate (KMnO4)
Application in the synthesis of Saccharin: Me
SO2NH2
KMnO4
OH-
CO2
SO2NH2
Na
SO2
NH
O
Saccharin
Oxidation of terminal alkynes:
CO2H
6
Me
SO2Cl
(NH4)2CO3
KMnO4
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation Manganese dioxide (MnO2)
Excess of MnO2 is required
O
MnO2, KCNOH
EtOH
OH
CN
Uses: Selective oxidation of allylic & benzylic alcohols
O
CN
MnO2
CH2Cl2
OH
7
O
OEtEtOH
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation Manganese dioxide (MnO2)
8
OH
MnO2ROH
NaCNCO2R
OH MnO2
O
H
CN OH
CN
MnO2
O
CN
O
OR R OH
Manganese based oxidation
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
CH2OH CHO
MnO2 OHCHO
MnO2
DCM
OHCHO
MnO2 MnO2, CH2Cl2
HO
OH
O
OH
Manganese dioxide (MnO2)
9
OH
HO
MnO2
CHCl3
OH OH
O
OH
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Manganese based oxidation Manganese(lll) acetate Mn(OAc)3
O
Mn(OAc)3
OOAc
OOAcOMn(OAc)3
10
OHO OMn(OAc)2
Mn(OAc)3
Mn(OAc)2
OMn(OAc)3
O
Mn(OAc)2
OOAc
Manganese based oxidation
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
OH
Manganese(lll) acetate Mn(OAc)3
11
Mn(OAc)3
NMe
O
OH
NMe
O
O
NMe
O
O OH
NMe
O
O OHMn(OAc)3
Mn(OAc)2
NMe
O
OH OH
NMe
O
OOH
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Silver-based oxidation
R
O
H
Ag2OR
O
OH+ 2 Ag
Ag2CO3 on Celite (Fetizon’s reagent)
OHOH
Fetizon's reagent
O
O
Fetizon's reagent
O
OH
OH O
OH
O
Ag2O Mild oxidant to oxidize aldehyde to carboxylic acid
CHO Ag2O
NaOH
CO2H
Conversion of diols to lactones
12
Silver-based oxidation
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
Ag2CO3 on Celite (Fetizon’s reagent) Highly selective:
Mono-oxidation:
Mechanism:
OH OH OH
Fetizon's reagent
OH O OH
OHOH
Fetizon's reagent
OHO
Fetizon's reagent
OH
OH
O
OH
HO H
R R
Ag+ Ag+
O
O--O
O
O O
HH
R R
Ag
O
Ag+O
R RH2O + CO2 + 2Ag
13
CH-‐423 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan
R
R'
I2Ag(OAc)2 or Ag(O2CPh)2
R
R'I
O
OR
R'CH3
O
OR
R'CH3
R
R'
OAc
OAc
-OAc
H2O
R
R'
OH
OHcis product
R
R'
OH
OHtrans product
In absence of water, Prevost Hydroxylation, trans-product
In presence of water, Woodwards hydroxylation,
cis-product
Silver acetate
Silver-based oxidation
14
R
R'
I
O CH3
O
