Pinnick oxidation

[4] There exist many different reactions to oxidize aldehydes, but only a few are amenable to a broad range of functional groups.

The Pinnick oxidation has proven to be both tolerant of sensitive functionalities and capable of reacting with sterically hindered groups.

For example, HOCl can react with double bonds in the organic reactant or product via a halohydrin formation reaction.

[7] (See Limitation below) Also, solid-supported reagents such as phosphate-buffered silica gel supported by potassium permanganate and polymer-supported chlorite have been prepared and used to convert aldehydes to carboxylic acid without having to do conventional work-up procedures.

[7][9] Hydroxides, epoxides, benzyl ethers, halides including iodides and even stannanes are quite stable in the reaction.

Lower yields are obtained for reactions involving aliphatic α,β-unsaturated and more hydrophilic aldehydes.

In particular, chiral α-aminoaldehydes do not react well due to epimerization and because amino groups can be easily transformed to their corresponding N-oxides.

For example, Pinnick oxidation of thioanisaldehyde gives a high yield of carboxylic acid products, but with concomitant conversion of the thioether to the sulfoxide or sulfone.