Uta Sundermeier

Selective oxidation of alcohols in the presence of an Os/O2-system☆

Abstract The osmium-catalyzed oxidation of alcohols with molecular oxygen to give aldehydes in good to excellent yields has been developed. Best results are obtained by using a buffered two-phase system with a constant pH of 10.4. Under optimized reaction conditions a remarkable catalyst productivity (TON up to 16600) is observed.

Dihydroxylation of olefins using air as the terminal oxidant

Abstract 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 K 3 [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.

An improved version of the Sharpless asymmetric dihydroxylation

Abstract The osmium catalyzed asymmetric dihydroxylation of olefins (Sharpless AD) was studied under controlled pH conditions. It was found that providing a constant pH value of 12.0 leads to improved reaction rates for internal olefins. Hydrolysis aids such as methanesulfonamide can be omitted. For terminal olefins, working at a constant pH of 10.0 at room temperature leads to higher enantioselectivities compared to AD reactions without pH control.