Lemieux‐Johnson Reagent

Lemieux‐Johnson Reagent / Lemieux–Johnson Oxidation

The Lemieux-Johnson reagent is a combination of osmium tetroxide (OsO₄) and sodium periodate (NaIO₄) used for oxidative cleavage of carbon-carbon double bonds in alkenes. This cleavage produces aldehydes or ketones, similar to the results of reductive ozonolysis. This is also known as Lemieux–Johnson oxidation.

Mechanism of Lemieux–Johnson Oxidation

The reaction involves the formation of cyclic osmate ester, which undergoes oxidative cleavage with NaIO₄ to give the dicarbonyl compounds

The reaction involves two steps:

Step-1: Dihydroxylation: OsO₄ adds hydroxyl groups across the double bond (syn-addition), forming a 1,2-diol (cis-diol not trans-diol).

Step-2: Oxidative Cleavage: NaIO₄ then cleaves the diol, forming the aldehydes or ketones.