Chiral BINAP-based hierarchical porous polymers as platforms for efficient heterogeneous asymmetric catalysis

Two vinyl-functionalized chiral 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) ligands, (S)-4,4'-divinyl-BINAP and (S)-5,5'-divinyl-BINAP, were successfully synthesized. Chiral BINAP-based porous organic polymers (POPs), denoted as 4-BINAP@POPs and 5-BINAP@POPs, were efficiently prepared via the copolymerization of vinyl-functionalized BINAP with divinyl benzene under solvothermal conditions. Thorough characterization using nuclear magnetic resonance spectroscopy, thermogravimetric analysis, extended X-ray absorption fine structure analysis, and high-angle annular dark-field scanning transmission electron microscopy, we confirmed that chiral BINAP groups were successfully incorporated into the structure of the materials considered to contain hierarchical pores. Ru was introduced as a catalytic species into the POPs using different synthetic routes. Systematic investigation of the resultant chiral Ru/POP catalysts for heterogeneous-asymmetric hydrogenation of beta-keto esters revealed their excellent chiral inducibility as well as high activity and stability. Our work thereby paves a path towards the use of advanced hierarchical porous polymers as solid chiral platforms for heterogeneous asymmetric catalysis. (c) 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.