Osmium tetroxide stoichiometry

From the practical perspective of laboratory use, the catalytic AD process requires a minimum of concern over stoichiometry. The new osmium tetroxide-chiral ligand complexes are so efficient that for most olefins, 0.2 mol % of osmium will provide a satisfactory rate of reaction at 0°C [291. In the occasional case where hydroxylation is slow under these conditions, the quantity of osmium in the catalyst should be increased to 1 mol % and the reaction temperature kept at 0 °C. In the rare case where hydroxylation is still slow under these conditions, the temperature may be raised to 25°C and, to ensure no loss in enantioselectivity, the ligand concentration may be increased from 1 mol % to 2 mol %. 

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