Influence of Ionic Liquid Film Thickness and Flow Rate on Macrocyclization Efficiency and Selectivity in Supported Ionic Liquid-Liquid Phase Catalysis.

Supported ionic-liquid phase (SILP) technology in a biphasic setting with n-heptane as the transport phase was applied to the Ru-alkylidene-N-heterocyclic carbene (NHC) catalyzed macrocyclization of α,ω-dienes to elucidate the effect of ionic liquid (IL)-film thickness, flow rate as well as substrate and product concentration on macrocyclization efficiency, and Z-selectivity. To understand the molecular-level behavior of the substrates and products at the n-heptane/IL interphase, atomistic molecular dynamics simulations were conducted and correlated with experimental observations. The thickness of the IL layer strongly influences the Z/E ratio of the products in that a thin IL layer favors higher Z/E ratios by confining the catalyst between the pore wall and the liquid-liquid interphase whereas a thick IL layer favors formation of the E-product and Ru-hydride catalyzed isomerization reactions. Also, macrocyclization efficiency, expressed by the ratio of oligomers/macromonocycle (O/MMC), is influenced both by the flow rate and the thickness of the IL layer.