Synthesis of Pd-stabilized chiral conjugated microporous polymer composites as high efficiency heterogeneous asymmetric Henry reaction catalysts

Abstract

Chiral conjugated microporous polymers (CCMPs) containing amide groups were designed and synthesized by Sonogashira coupling polymerization. CCMPs are reported for the first time as heterogeneous asymmetric catalyst platforms for the stabilization of Pd with applications in asymmetric catalytic synthesis. Four Pd/CCMPs heterogeneous catalysts exhibited efficient catalytic activity (of up to 87% yield) and excellent enantioselectivity (of up to 97% enantiomeric excess value) in the asymmetric Henry reaction, with a wide range of substrates and easy recovery. The Pd/CCMPs composites could be easily recycled and maintained catalytic activity after 3 cycles of reactions. A rational catalytic cycle was proposed to further understand the role of Pd/CCMPs in the Henry reaction. This study greatly extends the application of CCMPs in heterogeneous asymmetric catalysis.