Ruthenium Carbenes Supported on Mesoporous Silicas as Highly Active and Selective Hybrid Catalysts for Olefin Metathesis Reactions under Continuous Flow

Abstract In the search for a highly active and selective heterogenized metathesis catalyst, we systematically varied the pore geometry and size of various silica‐based mesoporous (i.e., MCM‐41, MCM‐48, and SBA‐15) and microporous (ZSM‐5 and MWW) versus macroporous materials (D11‐10 and Aerosil 200), besides other process parameters (temperature, dilution, and mean residence time). The activity and, especially, selectivity of such “linker‐free” supports for ruthenium metathesis catalysts were evaluated in the cyclodimerization of cis ‐cyclooctene to form 1,9‐cyclohexadecadiene, a valuable intermediate in the flavor and fragrance industry. The optimized material showed not only exceptionally high selectivity to the valuable product, but also turned out to be a truly heterogeneous catalyst with superior activity relative to the unsupported homogeneous complex.