Aerobic oxidation of alkenes to esters of vicinal diols with a syn-configuration catalyzed by I₂ and the H₅PV ₂Mo₁₀O₄₀ polyoxometalate

A new method for the synthesis of vicinal diols from alkenes has been developed. Reaction of molecular iodine in the presence of a polyoxometalate as oxidation catalyst under aerobic conditions in acetic acid solvent leads to the oxidative iodoacetoxylation of an alkene, i.e. formation of a 1,2-iodoacetate. Further in situ substitution of the iodide by water yields the 1,2-diol monoacetate with a predominantly (ca. 4.5:1) cis-configuration. Further esterification under the reaction's acidic conditions leads also to the cis-diacetate. The method may be valuable for the synthesis of cis-vicinal diols without use of toxic osmium catalysts.