Oxidation 1. Oxidation of Alcohol a. Cr oxidation : Mechanism

i) Jone’s reagent : CrO 3 + H 2 SO 4 + acetone --- acidic No racemization ii) Collins reagent : CrO 3 + pyridine --- basic iii) PCC : CrO 3 + HCl + pyridine --- acidic iv) PDC : CrO pyridine --- less acidic

b. Mn oxidation : i) KMnO 4 : solubility problem, over-oxidation problem ii) MnO 2 : mild oxidant, requires activation R is only benzylic or allylic c. Ru oxidation : i) RuO 4 : RuO 2 + oxidants( IO 4 -, NaOCl)

ii) TPAP : Pr 4 NRuO 4 -- catalyst + oxidants( NMO) c. Activated sulfides : i) Moffatt oxidation : DMSO + DCC Suitable for 1,2-diol oxidation : cf.) metal oxidants cleave C-C bond

ii) Swern oxidation : DMSO + oxallyl chloride + Nt 3 N iii) Corey-Kim : DMS + NCS d. Dess-Martin reagent : periodinane – most mild but strong oxidant Moisture sensitive

2. Oxidation of Aldehyde Not so reliable Reliable, not scalable Mechanism based Org. Lett. 5, 2003, 1031

Unusual oxidizing agents Mostly lactol oxidation

Unusual oxidizing agents

3. Epoxidation of olefin Becomes more reactive with electron withdrawing R Most popular a. Peracid : electrophilic reagent b. HOONa : nucleophilic reagent More substituted one reacts faster, Electron donating group accelerates the reaction Mechanism

c. dioxirane Generation : Ketone + oxone d. Sharpless epoxidation I. : selective oxidation of allylic alcohols t-BuOOH + VO(acac) 2 or Mo(CO) 6

e. Asymmetric epoxidation i) Sharpless epoxidation II. : t-BuOOH + Ti(Oi-Pr) 4 + tartarate ester When R 1 is small e.e. > 90% Mechanism? : see Org. Rxn. V48, 1 (1996)

ii) Jacobsen epoxidation : catalyst + NaOCl Mechanism catalyst Jacobsen’s early proposal

ii) Jacobsen epoxidation : catalyst + NaOCl Mechanism catalyst

e. Asymmetric epoxidation iii) Chiral dioxirane : catalyst reagent

e. Asymmetric epoxidation iv) Conjugated system : JACS 2001, 123, 9474 Cat. = La(OiPr) 3 - BINOL-Ph 3 As=O TL 2006, 47, 99

3. dihydroxylation of olefin OsO 4 : i) Stoicheometirc or catalytic with N-oxides Cis- diol ii) Asymmetric dihydroxylation

3. dihydroxylation of olefin ii) Asymmetric dihydroxylation 95% e.e. JACS 1987, 109, 6213

iii) Catalytic asymmetric dihydroxylation

iv) Catalytic asymmetric aminohydroxylation

5.cleavage of olefin a. ozonolysis : O 3 electrophilic reagent -- not a clean reaction

6. allylic oxidation of olefin b. Oxidation through diol : - IO 4 a. Singlet oxygen Ene reaction --- allylic transposition c. Direct oxidation with OsO 4 JACS, 124, 2002, 3824

6. allylic oxidation of olefin b. SeO 2 With t-BuOOH, catalytic SeO 2 Regio, stereo-selectivity

6. allylic oxidation of olefin c. CrO 3 via

Homework Chapter 12 : 1, 2, 4, 9 Due :