Support nitrogen-group donating

Herrmann and coworkers reported on the preparation of immobilized OSO4 on poly(4-vinyl pyridine) and its use in the dihydroxylation of alkenes by means of hydrogen peroxide [35]. However, the problems of gradual polymer decomposition and osmium leaching were not solved. 

In contrast to other typical 0s04-catalyzed dihydroxylations, where H20- Bu0H is used as solvent system, the best yields were obtained in H20-acetone-CH3CN. While the reaction was successfully carried out using NMO, moderate yields were obtained using trimethylamine N-oxide, and much lower yields were observed using hydrogen peroxide or potassium ferricyanide. The catalyst was recovered quantitatively by simple filtration and reused five times without any loss in activity. 

A study on the rate of conversion of the starting material showed that the reaction proceeds faster using OSO4 than using the microencapsulated catalyst. This is ascribed to the slower reoxidation of the microencapsulated osmium ester with NMO, compared to simple OSO4. 

Later on, acrylonitrile-butadiene-polystyrene (ABS) polymer was used as the support based on the same microencapsulation technique, and several alkenes. 

Microencapsulated OSO4 can function as a reservoir and an efficient scavenger of homogeneous catalytic species [42, 43]. Hence, it gives results comparable to those achieved by its homogeneous analog. 

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