Reversible Microencapsulation of Pybox-Ru Catalysts

Significance

A microencapsulated chiral pybox-ruthenium complex was prepared, and a cyclopropanation reaction was carried out to evaluate the catalytic activity of the complex. The microencapsulated pybox-ruthenium complex was prepared by mixing linear polystyrene with pybox-ruthenium complex. Cyclopropanation of styrene with ethyl diazoacetate took place in the presence of the microencapsulated pybox-ruthenium complex to give cis- and trans-cyclopropanes in 62% yield with 83% ee and 52% ee. The polymeric ruthenium complex is dissolved in CH₂Cl₂ to provide a homogeneous mixture during the reaction. After the reaction was completed, hexane was added to the reaction mixture to precipitate the catalyst, which was then recovered by filtration. The catalyst could be reused two times without significant loss of activity and selectivity, although the catalytic activity decreased in the fourth run.