ON THE MECHANISM OF CATALYTIC ASYMMETRIC DIHYDROXYLATION (AD) OF ALKENES

Evidence in support of the asymmetric dihydroxylation (AD) of alkenes to proceed possibly by a trigonal bipyramidal structure in which OsO4 is coordinated independently to the bridgehead nitrogen of bisalkaloid derivatives and not through a hexacoordinated mu-oxo-bridged bisosmiu m (VIII) is provided. Roth the quinuclidine moieties of the ligand are independently coordinated to one molecule of osmium tetroxide; howeve r, in catalytic AD reaction only one of the osmium tetroxide reacts wi th the olefin.