Dihydroxylation of olefins using air as the terminal oxidant

A study of the osmium-catalyzed dihydroxylation of various olefins using air as the stoichiometric oxidant is described. Dihydroxylation takes place smoothly at an air pressure of 20 bar, at 50°C and pH 10.4. In the presence of dihydroquinine or dihydroquinidine derivatives (Sharpless ligands) asymmetric dihydroxylations occur with only slightly lower enantioselectivities compared to the classical K3[Fe(CN)6] reoxidation system. In the case of stilbene the solvent system is crucial in determining the chemoselectivity of the reaction. The first example of a selective metal catalyzed oxidative cleavage of an olefin with air to give aldehydes is presented.