Achiral osmium oxidation

With the bisalkaloid ligands, potassium ferricyanide can be used as the stoichiometric oxidant [84, 91]. As with the parent achiral osmium oxidation, NMMO can also be used as the oxidant (see above) [92]. However, rather than using NMMO in stoichiometric amounts, this morpholine component can be used in catalytic amounts by the addition of the biomimetic flavin 4 to set up a triple catalytic system where hydrogen peroxide is the oxidant [93-95], Methyltrioxorhenium can be used in place of the flavin mimic [96], as can tungsten(VI) [97] and carbon dioxide [98]. 

With this reaction, two new asymmetric centers can be generated in one step from an achiral precursor in moderate to good enantiomeric purity by using a chiral catalyst for oxidation. The Sharpless dihydroxylation has been developed from the earlier y -dihydroxylation of alkenes with osmium tetroxide, which usually led to a racemic mixture. 

X-Ray, NMR, kinetic analyses, and theoretical approaches have provided insight into the mechanism for both the achiral and asymmetric osmium-catalyzed oxidations of alkenes [64, 77, 81, 108-119]. 

Syn hydroxylation of ds-2-butene gives meso-2,3-butanediol because the meso compound is achiral, the product is optically inactive. Syn hydroxylation of trans-2-butene gives racemic 2,3-butanediol. Because the diol is formed as a racemic mixture, the product of the oxidation of the frans-alkene is also optically inactive. Thus, the osmium tetroxide oxidation of an alkene is stereospecific the stereochemistry of the product depends on the stereochemistry of the starting alkene. 

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