Cooperatively Catalyzed Henry Reaction through Directed Metal‐Chitosan Interactions

Abstract

AbstractThe main focus of the present work is on identifying the critical parameters involved in inducing acid‐base cooperative catalytic interaction in hybrid metal‐polymer materials. To makes these hybrid materials Ti or Sn acid sites are grafted to the hydroxy groups of chitosan (CS). The cooperative catalytic interactions between the Ti/Sn and the primary amine sites on CS are tested for the nitro‐aldol condensation of nitromethane with 4‐nitro‐benzaldehyde. The observed results show that the synthesis conditions have a pronounce effect on the 3D arrangement of the hybrid materials, which in turn affect the reaction activity and selectivity. The catalysts are characterized using N2‐pysisorption, XRD, FTIR, XPS and HRTEM in conjunctions with reaction kinetic analysis. Using the combined results, a reaction mechanism is proposed, which emphasizes the effect of proximity and orientation of the Lewis acid (Ti or Sn) and base (NH2) active sites on cooperative catalysis in the Henry reaction.