Pyridinium chlorochromate adsorbed

OXIDATION WITH PYRIDINIUM CHLOROCHROMATE ADSORBED ON ALUMINA... 

Oxidation and Reduction.—Pyridinium chlorochromate adsorbed on alumina has been reported as a selective oxidant cholesterol was converted in high yield into cholest-5-en-3-one. Similar oxidations have been reported with CrOs in Et20-CH2Cl2 in the presence of celite ° and with NaOCl-AcOH. When chromic acid in an acidic medium was used to oxidize steroidal allylic acetates to the corresponding a,/3-unsaturated ketones the quasi-axial acetates were more reactive than their quasi-equatorial epimers. Cholesterol and cholest-4-en-3/8-ol were converted, with Raney nickel and cyclohexanone in toluene, into 5/8-cholestanone in modest yield. 

Pyridinium chlorochromate adsorbed on alumina offers advantages over PCC alone in the oxidation of acid-sensitive molecules.For example, citronellol is oxidized to citronellal in 90% yield by the supported reagent, whereas PCC gives pulegone. Clay-supported iron(lll) nitrate is reported to oxidize secondary alcohols in good yield."... 

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