Aerobic Oxidation of Alkenes to Esters of Vicinal Diols with a syn-Configuration Catalyzed by I2 and the H5PV2Mo10O40 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 cisdiacetate. The method may be valuable for the synthesis of cis-vicinal diols without use of toxic osmium catalysts.