Design,Synthesis And Catalytic Properties Of Chiral Covalent Organic Frameworks

Owing to their permanent porosity,highly ordered and extended structure,highly chemical stability,and tunability,covalent organic frameworks(COFs)have emerged as a new type of organic materials that can offer various applications in different fields.Benefiting from the huge database of organic reactions,the required functionality of COFs can be readily achieved by modification of the corresponding organic functional groups on either polymerizable monomers or established COF frameworks.This striking feature allows chiral covalent organic frameworks to be reasonably designed and synthesized,as well as their use as a unique platform to fabricate asymmetric catalysts.This thesis studies the design and synthesis of chiral COFs,and their application in heterogeneous asymmetric catalysis.This thesis is divided into the following three parts:1.We study two porphyrin-containing chiral covalent organic framework(CCOF)-based composite catalysts which are loaded metal nanoparticles(M NP),and their application in the thermally-driven asymmetric one-pot Henry and A3-coupling reactions.All the reactions are conducted at elevated temperatures with both excellent stereoselectivity and yield which resulted from the synergy of CCOF confinement effect and M NP catalytic activation.Notably,the needed thermal energy for the asymmetric reactions herein is derived from the photothermal conversion via porphyrin-based CCOF upon irradiation with visible light.Remarkably,the CCOF confinement effect can be effectively maintained up to 100 ? for the asymmetric one-pot Henry and A3-coupling reactions.2.(S)-2-(2-Chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)acetonitr ile((S)-CIK)is a key intermediate in the synthesis of(S)-clopidogrel,which is one of the most saleable worldwide antiplatelet and antithrombotic drugs.We show a facile method for the direct synthesis of(S)-CIK via Strecker reaction using a chiral covalent framework catalyst in a heterogeneous way.The asymmetric synthesis involves a photothermal-conversion-triggered,thermally driven reaction which affords(S)-CIK in 98% yield with 94% enantiomeric excess under visible-light irradiation.Furthermore,the above approach is readily extended to a gram-scale level on a fixed-bed continuous-flow model reactor.The potential utility of this strategy is highlighted by the preparation of many more other types of chiral drugs and drug intermediates in a green and facile way.3.(R)-2-methyl-3-(pyridin-4-yl)propanal(R-MPP)is a key synthon to bioactive drugs and natural products.We report herein a new and facile synthetic approach for the synthesis of(R)-MPP via enantioselective ?-benzylation of propanal using a multifunctional chiral covalent framework catalyst in a heterogeneous way.The integration of chiral BINOL-phosphoric acid and Cu(II)-porphyrin modules into a single COF framework endows the obtained(R)-Cu TAPBP-COF with robust chiral confinement space,visible-light induced photothermal conversion,and coexisting Br?nsted and Lewis acidic sites,which allow it to promote a thermally-driven synthesis of(R)-MPP in 98% yield(95% ee)by cooperative catalysis in a single catalytic cycle via visible-light induced photothermal conversion.