Criegee oxidation

Two mechanisms are proposed for the Criegee oxidation, depending on the configuration of the diol. If the oxygen atoms of the two hydroxy groups are conformationally close enough to form a five-membered ring with the lead atom, the reaction occurs via a cyclic intermediate. If the structure cannot adopt such a conformation, an alternate mechanism is possible, but is slower. Trans-fused five member rings are heavily strained, thus trans-diols that are on a five-membered ring will react slower than cis-alcohols on such a structure. == Modifications ==

Although the classic substrate for the Criegee oxidation are 1,2-diols, the oxidation can be employed with β-amino alcohols, α-hydroxy carbonyls, and α-keto acids, In the case of β-amino alcohols, a free radical mechanism is proposed. The Criegee oxidation can also be employed with 2,3-epoxy alcohols forms α-acetoxy carbonyls. Because the substrates can be produced with specific stereochemistry, such as by Sharpless epoxidation of allylic alcohols, this process can yield chiral molecules. Criegee oxidations are commonly used in carbohydrate chemistry to cleave 1,2-glycols and differentiate between different kinds of glycol groups. == References ==