The document discusses several chemoselective reagents for alcohol oxidation, including activated manganese dioxide, barium manganate, silver carbonate on celite (Fetizon's reagent), TEMPO, ceric ammonium nitrate, and sodium hypochlorite. Each reagent has advantages and disadvantages in selectively oxidizing certain alcohol functional groups, such as allylic, benzylic, and secondary alcohols, over saturated or primary alcohols under mild conditions. Fetizon's reagent and TEMPO are particularly useful for oxidizing alcohols without racemization of chiral centers.

1. Chemoselective Reagents
for Alcohol Oxidation

2. Activated Manganese Dioxide
• Highly chemoselective oxidant
• allylic, benzylic, and propargylic alcohols are oxidized faster
than saturated alohols
• mild conditions in H20, acetone, or CHCl3

3. Activated Manganese Dioxide cont.....
Disadvantage
• large excess of MnO2 ( ~40 equivalents )
• long reaction times
• difficulty to obtain highly activated MnO2

4. Barium Manganate
• Similar chemoselectivities as MnO2
Advantages
• readily available
• does not require special treatment for activation

5. Barium Manganate cont.....

6. Silver Carbonate on Celite
(Fetizon's Reagent)
• Useful for small-scale oxidations the products are recovered
in high purity by simply filtering the Ag(0) and evaporating
the solvent.
• The ease of alcohol oxidation :
allylic, benzylic-OH > 2° ROH > 1° ROH
• Highly hindered -OH groups are not oxidized

7. Fetizon's reagent cont.....
• Oxidation of allylic alpha, omega-diols gives high yields of
five- or six-member ring lactone
•
•
• Oxidize lactols (hemiacetals) to lactone

8. TEMPO
2.2.6.6-Tetramethyl-1-piperidinyl
• Nitroxyl radical-containing reagent
• catalyzes the oxidation of primary and secondary alcohols in
conjunction with co-oxidants (oxygen, hypochlorite, bromite,
hypervalent iodine, or peroxy acids).
• particularly useful for the oxidation of optically active alpha-
alkoxy- or alpha-amino alcohols to the corresponding aldehydes
without loss of enantiomeric purity

9. TEMPO cont......
• chemoselective for primary alcohols
• secondary alcohols are oxidized slowly

10. Ceric Ammonium Nitrate
• Chemoselective oxidation of a secondary OH group
in the presence of a primary OH group achieved
with (NH4)2Ce(NO3)6, NaBrO3
• does not tolerate the presence of double bond

11. Sodium Hypochlorite
• Chemoselective oxidation of a secondary OH group
in the presence of a primary OH group is possible
with NaOCl in aqueous acetic acid