Osmylation features

The same features are observed in the osmylation of arene donors. Thus, osmium tetra-oxide spontaneously forms complexes with arenes, and the systematic spectral shift in the CT bands parallels the decrease in the arene IP [59]. The same osmylated adducts are obtained thermally on leaving mixtures to stand in the dark or upon irradiation of the CT bands at low temperature. Time-resolved spectroscopy establishes that irradiation of the CT band of the anthracene/osmium tetraoxide complex leads directly to the radical-ion pair ANT+, 0s04, which then collapses to the osmium adduct (with a rate constant fc 109 s 1) in competition with back ET [59]. 

Common Features in Thermal and Charge-tranter Osmylations... 

Common Features in Thermal and Charge-transfer Osmylations 7.4.43 Electron Transfer in the Charge-transfer Osmylation ofArenes 7.4.4.6 Electron Transfer as the Common Theme in Arene Osmylation... 

Whereas OSO4 and the 0x0 esters considered below possess certain features unique to osmium, analogues of the osmyl complexes are found for other elements capable of attaining configura-... 

Common Features inThermal and Charge-transfer Osmylations 865... 

The avoidance of a-ketol by-products is an important feature of a new catalytic osmylation procedure for the preparation of cis-1,2-diols. Reaction involves treatment of the olefin with N-methylmorpholine iV-oxide dihydrate in aqueous acetone, and osmium tetroxide in t-butyl alcohol at 25 °C, overnight. Reduction (NaHS03), adsorption on to magnesium silicate, filtration, neutralization, and ethyl acetate extraction afforded the diols in moderate to excellent yield. An example is the synthesis of (397 55 %) from (396). 

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