Application of Heterogeneous Polymer-Supported Catalysts to Continuous Flow Systems

Organic transformations using continuous-flow reactors containing polymer-supported catalysts have recently attracted much attention in synthetic organic chemistry. The continuous-flow reaction systems provide safe, green-sustainable, efficient, reliable, and practical methods to prepare valuable organic compounds. Herein we report our recent development of the continuous-flow reaction systems using packed catalyst cartridges of platinum and iron nanoparticles dispersed in an amphiphilic polystyrene-poly(ethylene glycol) polymer (ARP-Pt or ARP-Fe), and a macroporous polymeric acid catalyst. The continuous-flow system containing ARP-Pt catalyst showed dual functions to catalyze the oxidation of alcohols with O2 as well as the reduction of olefins and nitrobenzenes with H2 to give the corresponding products in high yield. Iron nanoparticles dispersed in an amphiphilic polymer (ARP-Fe) were also applied to the catalytic hydrogenation of olefins, aromatic imines, and aldehydes under flow conditions. Moreover, the direct esterification of carboxylic acids was achieved by using the column-packed macroporous polymeric acid catalyst under mild conditions in a flow manner without removal of water, which was successfully applied to the biofuel preparation.