The chemical transformation of CO2under mild conditions remains a great challenge because of itsexceptional kinetic and thermodynamic stability.Two important reactions in the transformation ofCO2are the N‐formylation...The chemical transformation of CO2under mild conditions remains a great challenge because of itsexceptional kinetic and thermodynamic stability.Two important reactions in the transformation ofCO2are the N‐formylation reaction of amines using hydrosilanes and CO2,and the cycloaddition ofCO2to epoxides.Here,we report the high efficiency of bifunctional metallosalen complexes bearingquaternary phosphonium salts in catalyzing both of these reactions under solvent‐free,mild conditionswithout the need for co‐catalysts.The catalysts’bifunctionality is attributed to an intramolecularcooperative process between the metal center and the halogen anion.Depending on the reaction,this activates CO2by permitting either the synergistic activation of Si–H bond via metal–hydrogen coordinative bond(M–H)or the dual activation of epoxide via metal–oxygen coordinativebond(M–O).The one‐component catalysts are also shown to be easily recovered and reusedfive times without significant loss of activity or selectivity.The current results are combined withprevious work in the area to propose the relevant reaction mechanisms.展开更多
Tannic acid （TA）/KI as a cheap,green,highly-efficient,biocompatible,and recyclable catalytic system represents the excellent synergistic effect in the cycloaddition reactions of CO2 and epoxides under solvent-free c...Tannic acid （TA）/KI as a cheap,green,highly-efficient,biocompatible,and recyclable catalytic system represents the excellent synergistic effect in the cycloaddition reactions of CO2 and epoxides under solvent-free conditions,which is originated from hydrogen bonding between the hydrogen atoms of phenolic hydroxyl groups within TA and the oxygen atom of the epoxide.Therefore,it is considerable to be a sustainable methodology for the utilization of bio-resources.展开更多
A variety of unique Al(salen) complexes functionalized by imidazolium-based ionic liquid(IL) moieties with the salen ligand at the two sides of 3,3′-position have been successfully prepared, rather than familiar 5,5...A variety of unique Al(salen) complexes functionalized by imidazolium-based ionic liquid(IL) moieties with the salen ligand at the two sides of 3,3′-position have been successfully prepared, rather than familiar 5,5′-position reported previously.The catalytic activity obtained by these bifunctional catalysts could be superior to those of the binary type catalysts in the formation of five-membered heterocyclic compounds from the cycloaddition reaction of CO_2 and three-membered heterocyclic compounds(including terminal epoxides and N-substituted aziridines), presumably due to the distinguished intramolecularly synergistic catalysis, which might lead to perform the cycloaddition reaction at ambient conditions and retain excellent yield and unprecedented chemo-or regioselectivity. Moreover, the polyether-based trifunctional Al(salen) catalysts with the best catalytic performance could be regenerated and reused at least eight times without any obvious decreases in catalytic activity. Finally,the kinetic investigation suggested the structure of catalysts had important influences on the catalytic activity, thereby proposing the possible reaction mechanism.展开更多
基金supported by the National Natural Science Foundation of China (21676306,21425627)the National Key Research and Development Program of China (2016YFA0602900)the Natural Science Foundation of Guangdong Province (2016A030310211,2015A030313104)~~
文摘The chemical transformation of CO2under mild conditions remains a great challenge because of itsexceptional kinetic and thermodynamic stability.Two important reactions in the transformation ofCO2are the N‐formylation reaction of amines using hydrosilanes and CO2,and the cycloaddition ofCO2to epoxides.Here,we report the high efficiency of bifunctional metallosalen complexes bearingquaternary phosphonium salts in catalyzing both of these reactions under solvent‐free,mild conditionswithout the need for co‐catalysts.The catalysts’bifunctionality is attributed to an intramolecularcooperative process between the metal center and the halogen anion.Depending on the reaction,this activates CO2by permitting either the synergistic activation of Si–H bond via metal–hydrogen coordinative bond(M–H)or the dual activation of epoxide via metal–oxygen coordinativebond(M–O).The one‐component catalysts are also shown to be easily recovered and reusedfive times without significant loss of activity or selectivity.The current results are combined withprevious work in the area to propose the relevant reaction mechanisms.
文摘Tannic acid （TA）/KI as a cheap,green,highly-efficient,biocompatible,and recyclable catalytic system represents the excellent synergistic effect in the cycloaddition reactions of CO2 and epoxides under solvent-free conditions,which is originated from hydrogen bonding between the hydrogen atoms of phenolic hydroxyl groups within TA and the oxygen atom of the epoxide.Therefore,it is considerable to be a sustainable methodology for the utilization of bio-resources.
基金supported by the National Science for Distinguished Young Scholars of China(21425627)the National Natural Science Foundation of China(21676306)+1 种基金the Natural Science Foundation of Guangdong Province(2016A030310211,2015A030313104)the Fundamental Research Funds for the Central Universities of Sun Yat-sen University
文摘A variety of unique Al(salen) complexes functionalized by imidazolium-based ionic liquid(IL) moieties with the salen ligand at the two sides of 3,3′-position have been successfully prepared, rather than familiar 5,5′-position reported previously.The catalytic activity obtained by these bifunctional catalysts could be superior to those of the binary type catalysts in the formation of five-membered heterocyclic compounds from the cycloaddition reaction of CO_2 and three-membered heterocyclic compounds(including terminal epoxides and N-substituted aziridines), presumably due to the distinguished intramolecularly synergistic catalysis, which might lead to perform the cycloaddition reaction at ambient conditions and retain excellent yield and unprecedented chemo-or regioselectivity. Moreover, the polyether-based trifunctional Al(salen) catalysts with the best catalytic performance could be regenerated and reused at least eight times without any obvious decreases in catalytic activity. Finally,the kinetic investigation suggested the structure of catalysts had important influences on the catalytic activity, thereby proposing the possible reaction mechanism.
