Abstract
For seeking high enantiopurity, the previously reported thermal asymmetric catalysis is usually carried out at low temperature sometimes with limited yield, that is, the high enantiomeric excess (ee) usually at the cost of high yield. Thus, the achieving both high stereoselectivity and yield is an enormous challenge. We report herein two metal nanoparticle (M NP)-loaded and porphyrin-containing homochiral covalent organic framework (CCOF)-based composite catalysts, 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 °C for the asymmetric one-pot Henry and A3-coupling reactions herein.
Highlights
For seeking high enantiopurity, the previously reported thermal asymmetric catalysis is usually carried out at low temperature sometimes with limited yield, that is, the high enantiomeric excess usually at the cost of high yield
For meeting the multifaceted requirements of the thermallydriven asymmetric catalysis, we report two metal nanoparticle (M NP)-loaded and homochiral covalent organic framework (CCOF)-based asymmetric catalytic materials, termed as M@containing homochiral covalent organic framework (CCOF)-CuTPP (M=Au (2), Pd (3)), which are composed of a porphyrin-derived CCOF (CCOF-CuTPP (1)) and corresponding M NP
As mentioned above, M@CCOF-CuTPP of 2 (M=Au) and 3 (M=Pd) are the multifunctional catalytic materials and they can highly promote thermally-driven asymmetric catalysis at the elevated temperature by photothermal conversion
Summary
The previously reported thermal asymmetric catalysis is usually carried out at low temperature sometimes with limited yield, that is, the high enantiomeric excess (ee) usually at the cost of high yield The achieving both high stereoselectivity and yield is an enormous challenge. PTCMs-based photothermal chiral catalysis, especially natural sunlight triggered thermally-driven asymmetric synthesis, has attracted much less attention[4]. As it is known, both yield and enantioselectivity are the crucial indicators for the chiral synthesis, and the achieving high yield with excellent enantiomeric excess (ee) is meaningful, especially for those important asymmetric organic transformations, such as asymmetric Henry and benzaldehyde–phenylacetylene–pyrrolidine A3-coupling reactions, that can transform the achiral compounds into the high value-added chiral organic chemicals. The optically active pyrrolidinederived propargylamine generated from the homogeneous CuIcatalyzed benzaldehyde–phenylacetylene–pyrrolidine A3-coupling can be achieved in high 92% yield and 92% ee, but with the aid of the chiral acid-thiourea cocatalysts and molecular sieve at 0 °C31
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