Efficient and recyclable monomeric and dendritic Ru-based metathesis catalysts

Several highly active, recoverable and recyclable Ru-based metathesis catal ysts are presented. The crystal structure of Ru complex 5, bearing a 1,3-di mesityl-4,5-dihydroimidazol-2-ylidene and styrenyl ether ligand is disclose d. The heterocyclic ligand significantly enhances the catalytic activity, a nd the styrenyl ether allows for the easy recovery of the Ru complex. Catal yst 5 promotes ring-closing metathesis (RCM) and the efficient formation of various trisubstituted olefins at ambient temperature in high yield within 2 h; the catalyst is obtained in >95% yield after silica gel chromatograph y and can be used directly in subsequent reactions. Tetrasubstituted olefin s can also be synthesized by RCM reactions catalyzed by 5. In addition, the synthesis and catalytic activities of two dendritic and recyclable Ru-base d complexes are disclosed (32 and 33). Examples involving catalytic ring-cl osing, ring-opening, and cross metatheses are presented where, unlike monom er 5, dendritic 33 can be readily recovered.