Corey-Suggs oxidation

What is Corey-Suggs oxidation?

The first reported instance of the Corey-Suggs oxidation occurred in 1975, when they employed pyridinium chlorochromate (PCC) in dichloromethane as a solvent to convert primary and secondary alcohols into carbonyl compounds. This reaction has since become known as the Corey-Suggs oxidation, but is more commonly referred to as PCC oxidation.

Corey-Suggs oxidation
Corey-Suggs oxidation

R = alkyl, aryl
R’ = H, alkyl, aryl

PCC itself is also commonly called the Corey-Suggs reagent. While the initial report called for a 1:1 ratio of substrate to PCC for a complete oxidation, subsequent research has shown that the reaction only requires two electrons, meaning that a 1:1 ratio is sufficient for the conversion of alcohols to carbonyl compounds. The commercial availability, efficiency, shelf-stability, and versatility of PCC have made the Corey-Suggs oxidation a popular method in organic synthesis. However, due to the acidity of PCC, a tautomerization reaction always follows the generation of the carbonyl group, which can lead to product isomerization. It has been observed that under certain conditions, such as when a peroxide bond is present, cyclic acetal can be converted into lactone.

The oxidation of different hydroxyl groups can also exhibit selectivity, with allylic or benzylic alcohols oxidizing before regular alcohol groups. This selectivity can be improved with the addition of dimethylaminopyridine (DMAP) and the use of poly[vinylpyridinium] chlorochromate (PVPCC), which is faster than normal PCC. The oxidation of cyclicallyl alcohols with PCC can result in the transformation of α,β-unsaturated cycloketones, with the C=C double bond appearing on a different ring of the cyclic compound. However, tertiary cyclic allyl alcohol oxidation can lead to a rearrangement involving the migration of double bonds. The use of n-butylammonium chlorochromate (BACC) instead of PCC can make the oxidation homogeneous when 18-crown-6 is present, and ultrasound agitation can also improve the Corey-Suggs oxidation. Finally, it has been observed that under the Corey-Suggs oxidation conditions, substrates with double bonds located five carbons from the hydroxyl group can form cyclic ketones via tandem oxidation-cyclizationoxidation.

References

E.J. Corey, J.William Suggs,
Pyridinium chlorochromate. An efficient reagent for oxidation of primary and secondary alcohols to carbonyl compoundsTetrahedron Letters 16 (31) 2647-2650 (1975)
DOI: 10.1016/S0040-4039(00)75204-X

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