Oxidation Flashcards
(34 cards)
@Ox: Side reaction generate MTM from DMSO (Pummerer Rearangement)
R-OH attack to (CH2=S-CH3)+ generate from the dissociation of sulfoium ylide intermediate.
@Oppenauer Ox is related to
Meerwein-Pondorff-Verley Reduction (Acetone, Metal alkoxide)
How to activate MnO2?
By adding activated carbon.
C could be activated by make fine powder and high heat.
What is oxone
2KHSO5.KHSO4.K2SO4
TIPS, TBS
Triisopropylsilyl, t-butyldimetylsilyl
Wt’ll include in this course?
+ Oxidation
+ Protecting group
+ Name reaction
+ Reagent
Some info about DMSO:
High bp, could be seperated by NaCl sarturated
Need activation to form sulfonium ylide, side product MTM (CH3 2-3 ppm)
Can dissolve inorganic coumpounds
Activator 3eq, overnight, rt., 30-40eq DMSO
Me2S volatile; not good for multi gram scale
Name as many oxidation method as you can:
from alcohol to aldehyde or ketone
- Dimethylsulfoxide-mediated Ox
- Dess-Martin Periodinane (DMP)
- o-iodoxybenzoic acid (IBX)
- tetra-n-propylamonium perruthenate (TPAP)
- N-oxoamonium-mediated ox.
- Manganese dioxide
- Barium Manganate
- Oppenauer Ox
- Chromium (VI) oxidants
- Sodium hypochlorite
- N-bromosuccinimide (NBS)
- Bromine
- Cerium (IV) oxidants
DMSO-mediated ox include
- Swern Ox. (Oxalyl chloride) ~ -70 oC
- Pfitzner-Moffatt Procedure (DCC, EDC) ~
- Parikh-Doering Pro. (SO3.py) ~ -15 -> 23 oC
DMP
Short time reaction, single eq. of oxidant
IBX (o-iodoxybenzoic acid, heat and shock sensitive) is DMP’s precursor
H2O accelerate the reaction
Deprotection of PMB or MPM (Bn) by
DDQ (dichlorodicianoquinone)
IBX (o-iodoxybenzoic acid)
is a mild reagent for ox. of 1,2-diol
Prepare by o-iodobenzoic acid + oxone at 70 oC
2-6 eq IBX + DMSO form a,B-unsatuated carbonyl compound from corresponding alcohol or carbonyl compound.
TPAP (tetra n-propylamonium Perruthenate Pr4N+RuO4-)
mild and selective ox in various solvent.
in conjunction with stoichiometric ox. NMO (N-methylmorpholine-N-oxide) will create non-toxic, room temperature operating oxidant
TEMPO (2,2,6,6-tetramethylpiperidinyloxyl)
unstable but cannot buy.–> in situ
Mild and selective and stoichiometric oxidant
Use with various other stoichiometric oxidants:
m-CPBA; NaOCl (sodium hypochlorite);
BAIB [bis(acetoxy)-iodo]benzene
sodium bromite (NaBrO2)
Oxone (2KHSO5.KHSO4.K2SO4)
MnO2
Must be used in active form Could be deactivate by polar solvent 50-100 eq Can oxidate syn or anti vivinal diols Vinyl stannanes are not tolerate
BaMnO4 (Barium manganate)
allylic and benzylic alcohol only
Tertiary allylic alcohols could be oxidize by
Cromium (VI) oxidants
Collins reagent
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Corey’s reagent
CrO3.py2 (hydroscopic, 6 eq in chlorinated solvent). Prepare by adding CrO3 to pyridine.!!!!
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PCC (air stable, not very hydroscopic, 1.5 eq in DMF or DCE or a suspension with chlorinated solvents)
molecular seives can accelerate the rate of reaaction.
NaOCl (sodium hypochlorite)
oxidize 2o alcohol in the present of 1o ones.
Use with AcOH.
Could replace by Calcium hypochlorite (a stable, easy to handle solid hypochlorite oxidant.
NBS
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bromine
Ox II alcohol in the presence of I alcohols. (Create Br+, -OH more Nu will react.
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Br/AcOH can only oxidize activated alcohol (like lactol)
cbz is PG of?
How to deprotect?
Amine with at least 1 N-H
H2 (Pd/C)
Sodium chlorite (NaClO2)
A mild, inexpensive and selective reagent -CHO –> -COOH. Offen used with scavenger (2-methyl-2-butene, NaH2PO4, t-BuOH and H2O)
Dithiol protect aldehyde is a good PG it is stable in most of condition but could be easy to deprotect by
PIFA (CF3CO2)IPh, ACN, H2O at 0 oC
Phenyliodine (III) bis(trifloroacetate)
The PG if used < 8C –> Terrible smell!!!
Diazomethene (CH2N2)
N2 is one of the best LG in Org. Syn.
Methylation of -COOH
By-product could be easily removed because everything this volatile!!! How great!!!
