The asymmetric photocatalytic organic synthesis(APOS)process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source.However,it still lacks...The asymmetric photocatalytic organic synthesis(APOS)process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source.However,it still lacks efficient semiconductors with tunable band structures and has a low recycling stability.Herein,we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks(QH-COFs)with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetricα-alkylation of aldehydes by merging with a chiral secondary amine.Up to 94%ee was obtained over QH-COFs,and the activity of QH-COFs was significantly higher than those of inorganic semiconductors(e.g.,Ti O2,Bi VO4,and WO3)under similar conditions,which is mainly attributed to their narrow band gap and suitable band edge.As far as we know,QH-COFs are the most active semiconductors for asymmetricα-alkylation of aldehydes ever reported.The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts.Attributed to the tetrahydroquinoline linkage,QH-COFs showed extremely high recycling stability,which made practicals application possible.This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.展开更多
Developing chiral solid catalysts for asymmetric catalysis is desirable for the elimination of homogeneous catalysis flaws but remains an immense challenge.Herein,we report the immobilization of TsDPEN on SBA‐15 with...Developing chiral solid catalysts for asymmetric catalysis is desirable for the elimination of homogeneous catalysis flaws but remains an immense challenge.Herein,we report the immobilization of TsDPEN on SBA‐15 with an ionic liquid(IL)linkage via the one‐pot reaction of imidazole‐TsDPEN‐N‐Boc with 3‐(trimethoxysilyl)propyl bromide in the SBA‐15 mesopores.After coordination to Rh,the chiral solid catalysts could efficiently catalyze quinoline transfer hydrogenation,achieving 97%conversion with 93%ee,which was comparable to their homogeneous counterparts.The chiral solid catalyst with the IL linkage afforded much higher turnover frequency than that without the IL linkage(93 h^(–1)vs.33 h^(–1)),attributed to the phase transfer and formate‐enriching ability of the IL linkage.Furthermore,the effect of the pH on the reaction rate of the solid catalyst was investigated,preventing reaction rate retardation during the catalytic process.The tuning of the linkage group is an efficient approach for catalytic activity improvement of immobilized chiral catalysts.展开更多
The development of heterogeneous catalytic processes is crucial for the synthesis of chiral compounds for both academic and industrial applications.However,thus far,such achievements have remained elusive.Herein,we re...The development of heterogeneous catalytic processes is crucial for the synthesis of chiral compounds for both academic and industrial applications.However,thus far,such achievements have remained elusive.Herein,we report the heterogeneous asymmetric hydrogenation of 2-methylquinoline over solid chiral catalysts,which were prepared by the one-pot polymerization of(1R,2R)-N-(4-vinyl-benzenesulfonyl)-1,2-diphenylethane-1,2-diamine(VDPEN)and divinylbenzene(DVB)in the presence or absence of activated carbon(C)or carbon nanotubes(CNTs),followed by Ru coordination and anion exchange.The solid chiral catalysts were fully characterized by N2 sorption analysis,elemental analysis,TEM,FT-IR spectroscopy,and 13C CP-MAS NMR.All the solid chiral catalysts could efficiently catalyze the asymmetric hydrogenation of 2-methylquinoline to afford 2-methyl-1,2,3,4-tetrahydroquinoline with 90%ee.Studies have shown that polymer/C and polymer/CNTs composites are more active than pure polymers.The polymer/CNTs composite exhibited the highest activity among all the solid chiral catalysts under identical conditions,owing to the unique morphology of CNTs.The recycling stabilities of the solid chiral catalysts were greatly improved when ionic liquids(ILs)were employed as solvents;this is mainly attributed to the decreased leaching amount of anions owing to the confinement effect of ILs on ionic compounds.展开更多
文摘The asymmetric photocatalytic organic synthesis(APOS)process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source.However,it still lacks efficient semiconductors with tunable band structures and has a low recycling stability.Herein,we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks(QH-COFs)with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetricα-alkylation of aldehydes by merging with a chiral secondary amine.Up to 94%ee was obtained over QH-COFs,and the activity of QH-COFs was significantly higher than those of inorganic semiconductors(e.g.,Ti O2,Bi VO4,and WO3)under similar conditions,which is mainly attributed to their narrow band gap and suitable band edge.As far as we know,QH-COFs are the most active semiconductors for asymmetricα-alkylation of aldehydes ever reported.The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts.Attributed to the tetrahydroquinoline linkage,QH-COFs showed extremely high recycling stability,which made practicals application possible.This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.
文摘Developing chiral solid catalysts for asymmetric catalysis is desirable for the elimination of homogeneous catalysis flaws but remains an immense challenge.Herein,we report the immobilization of TsDPEN on SBA‐15 with an ionic liquid(IL)linkage via the one‐pot reaction of imidazole‐TsDPEN‐N‐Boc with 3‐(trimethoxysilyl)propyl bromide in the SBA‐15 mesopores.After coordination to Rh,the chiral solid catalysts could efficiently catalyze quinoline transfer hydrogenation,achieving 97%conversion with 93%ee,which was comparable to their homogeneous counterparts.The chiral solid catalyst with the IL linkage afforded much higher turnover frequency than that without the IL linkage(93 h^(–1)vs.33 h^(–1)),attributed to the phase transfer and formate‐enriching ability of the IL linkage.Furthermore,the effect of the pH on the reaction rate of the solid catalyst was investigated,preventing reaction rate retardation during the catalytic process.The tuning of the linkage group is an efficient approach for catalytic activity improvement of immobilized chiral catalysts.
基金supported by the National Natural Science Foundation of China (21733009, 21621063)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB17020200)~~
文摘The development of heterogeneous catalytic processes is crucial for the synthesis of chiral compounds for both academic and industrial applications.However,thus far,such achievements have remained elusive.Herein,we report the heterogeneous asymmetric hydrogenation of 2-methylquinoline over solid chiral catalysts,which were prepared by the one-pot polymerization of(1R,2R)-N-(4-vinyl-benzenesulfonyl)-1,2-diphenylethane-1,2-diamine(VDPEN)and divinylbenzene(DVB)in the presence or absence of activated carbon(C)or carbon nanotubes(CNTs),followed by Ru coordination and anion exchange.The solid chiral catalysts were fully characterized by N2 sorption analysis,elemental analysis,TEM,FT-IR spectroscopy,and 13C CP-MAS NMR.All the solid chiral catalysts could efficiently catalyze the asymmetric hydrogenation of 2-methylquinoline to afford 2-methyl-1,2,3,4-tetrahydroquinoline with 90%ee.Studies have shown that polymer/C and polymer/CNTs composites are more active than pure polymers.The polymer/CNTs composite exhibited the highest activity among all the solid chiral catalysts under identical conditions,owing to the unique morphology of CNTs.The recycling stabilities of the solid chiral catalysts were greatly improved when ionic liquids(ILs)were employed as solvents;this is mainly attributed to the decreased leaching amount of anions owing to the confinement effect of ILs on ionic compounds.
