1.3.3 Pyridinium Chlorochromate (PCC) Oxidation
This reagent is obtained by adding pyridine to a solution of CrO3 in hydrochloric acid. PCC oxidizes primary and secondary alcohols to aldehydes and ketones, respectively (Scheme 3). As PCC is slightly acidic so it may affect the acid sensitive groups. The powdered NaOAc is used along with PCC for the oxidation of the substrate containing acid labile groups. PCC is commercially available and could also be prepared.
|
G. Piancatelli,, Encylopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette, Ed., New York, 1995, 6, 4356. |
Oxidation of Alcohols
.
 |
 |
 |
Scheme 3 |
Another important use of PCC is the transformation of allylic tertiary alcohols to afford α,β-unsaturated ketones (Scheme 4). This reaction is thought to proceed via a [3,3]-sigmatropic rearrangement of allylic chromate ester to give new allylic chromate ester, which then undergoes oxidation to give the α,β-unsaturated ketone.
 |
 |
Scheme 4 |