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Chemistry. 2014 Aug 25;20(35):11019-28. doi: 10.1002/chem.201403002. Epub 2014 Jul 25.

Insights into the asymmetric heterogeneous catalysis in porous organic polymers: constructing a TADDOL-embedded chiral catalyst for studying the structure-activity relationship.

Author information

1
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu 730000 (P.R. China).

Abstract

Construction of porous organic polymers (POPs) as asymmetric catalysts remains as an important but challenging task. Herein, we exploit the "bottom-up" strategy to facilely synthesize an α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based chiral porous polymer (TADDOL-CPP) for highly efficient asymmetric catalysis. Constructed through the covalent linkages among the three-dimensional rigid monomers, TADDOL-CPP possesses hierarchical porous structure, high Brunauer-Emmett-Teller (BET) surface area, together with abundant and uniformly-distributed chiral sites. In the presence of [Ti(OiPr)4], TADDOL-CPP acts as a highly efficient and recyclable catalyst in the asymmetric addition of diethylzinc (Et2Zn) to aromatic aldehydes. Based on the direct observation of the key intermediates, the reaction mechanism has been revealed by solid-state (13)C magic-angle spinning (MAS) NMR spectroscopy. In combination with the catalytic testing results, characterization on the working catalyst provides further information for understanding the structure-activity relationship. We suggest that the catalytic activity of TADDOL-CPP is largely affected by the structural rigidity, cooperative catalysis, local chiral environment, and hierarchical porous framework. We expect that the information obtained herein will benefit to the designed synthesis of robust POP catalysts toward practical applications.

KEYWORDS:

NMR spectroscopy; chirality; heterogeneous catalysis; polymers; reaction mechanisms; structure-activity relationships

PMID:
25067808
DOI:
10.1002/chem.201403002

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