Exam Flashcards
Swern Oxidation
I, II OH -> -CHO, >=O
(COCl)2, DMSO 2eq, Et3N
-78->-50 oC (
Pfitzner-Moffatt Procedure
I, II OH -> -CHO, >=O
DMSO, DCC or EDC, TFA, pyr
excess DCC or EDC
~ 23 oC
Parikh-Doering Procedure
I, II OH -> -CHO, >=O
DMSO, SO3.pyr, DIEA, DCM
At or near ambient reaction temperature.
attractive for large scale reactions.
DMP (Dess-Martin Periodiane)
I, II OH -> -CHO, >=O
DMP, CH2Cl2, py
room temp. 1eq acelerate the reaction
0.2-2 h; single equivalent oxidant
IBX (2-iodobenzoic acid)
I, II OH -> -CHO, >=O II OH is more favour
Oxidize 1,2-diols without C-C bond cleavage
IBX/DMSO; may add toluene and other solvents
room temp.
Excess IBX –> a,b-unsaturated ketone from II-OH or ketone
Jones Oxidation
OH(I) -> COOH; OH(II) -> Ketone
Chromic acid in aqueous sulfuric acid.
Solvent: Acetone could react with excess oxidant.
Olefin may be isomerization.
1,2-diol and a-hydroxyketone susceptible to cleavage.
-10->23 oC
TEMPO, PhI(OAc)2 (BAIB)
OH(I) -> CHO if solvent is CH2Cl2
OH(II) -> Ketone
OH(I) -> acid if solvent is CH3CN/H2O (NaHCO3)
David ozaziridine (N-sulfonylozaziridine)
Ketone -> a-Hydroxy ketone prepared by biphasic oxidation of sulfonimine with m-CPBA or Oxone. -78->-20 oC 1. KHDMS, THF David azaziridine
Molybdenum peroxy compounds
MoO5.pyr.HMPA
(MoOPH)
Ketone -> a-Hydroxy ketone
- LDA, THF, -78 oC
- MoOPH (-40 oC)
Rubottom oxidation
Epoxidation of silyl enol ether and subsequent silyl migration –> a-Hydroxy ketone
m-CPBA or peroxide (dimethyldioxirane)
Fetizon’s reagent
Diol –> Lactone
Ag2CO3 on celite, C6H6
reflux (75-85 oC)
Other method (Pt/O2, acetone, H2O;;;; NaBrO2, DCM, NaHCO3 aq.;;;; RuH2(PPh3)4, PhCH=CHCOCH3, toluene)
Oxidative cleavage of diols
# NaIO4, NaOH, EtOH; 0-25 oC; 2h # Pb(OAc)4, PhH, 0 oC; 20-45 min a-Hydroxy ketone can be cleavage as well.
Ozone
most common for oxidative cleavage of olefins
alkene with electron-donating group are cleaved more readily than those with electron-withdrawing.
1. O3, (ClH2C)2, 0 oC
2. Me2S
alkenes are ozonized more readily than alkynes
ozonolysis of silyl enol ethers –> COOH
OsO4, NaIO4
alternative of Ozone method
less hindered olefins are cleaved selectively.
THF, H2O; 23 oC
can use 2,6-lutidine as a buffering agent
RuO4
C=C -> Aldehyde, ketone (cleavage) -OH to ketone diol -> dicarboxylic acid Usually generate in situ by RuO2.2H2O or RuCl3.H2O + NaIO4 solvent CCl4-ACN-H2O (1:1:1.5) 23 oC, 1h
Seagusa Oxidation
Ketone -> a,b-unsaturated ketone
- LiTMP, TMS-Cl (-78 oC)
- Pd (II), O2 or p-benzoquinone or diallyl carbonate; ACN
alternative to IBX
Selenation/Oxidation/Elimination
Ketone -> a,b-unsaturated ketone
- LDA, THF, -78 oC
- PhSeBr
- H2O2, py, CH2Cl2-H2O
SeO2
Alkene –> allylic alcohol
SeO2, t-BuOOH, DCM
0-23 oC
general method for oxidizing alkene to allylic alcohol
