The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads...The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads to substantial difficulty for chiral catalysts to provide sufficient enantiocontrol.Moreover,a racemic background process is often inevitable,further deteriorating enantioselectivity.In this regard,an effective protocol has been established for enantioselective intermolecular[2+2]photocycloadditions to overcome the challenges,which is capitalising on the ground-state preassociations of chiral catalysts with photoactivated substrates.Here,we report the viability of substrate-differentiating synergistic catalysis for this important reaction.In this new platform,energy transfer occurs between DPZ as a photosensitizer and enones or(E)-2-substituted vinylazaarenes for producing triplet-state species,and chiral phosphoric acid interacts with ground-state 2-vinylazaarenes via hydrogen bonding for subsequent enantiofacial cycloaddition.Although all active species are dispersed in the reaction system,valuable enantioenriched mono-and di-azaarene-functionalized cyclobutanes are obtained efficiently and selectively.In addition to constructing all-carbon quaternary stereocentres,flexible modulation of azaaryl groups and other substituents on the cyclobutane ring is also operative.展开更多
This report describes a new three‐component strategy for the regioselective synthesis of a series of tri‐substituted pyridazines via a 1,4‐diazabicyclo[2.2.2]octane （DABCO）‐catalyzed condensation of propiophenon...This report describes a new three‐component strategy for the regioselective synthesis of a series of tri‐substituted pyridazines via a 1,4‐diazabicyclo[2.2.2]octane （DABCO）‐catalyzed condensation of propiophenones, arylglyoxalmonohydrates and hydrazine hydrate in water. This method provides a green and convenient one‐pot route toward a diverse set of 3,6‐diaryl‐4‐methylpyridazines bearing various aryl substituents. This procedure is highly regioselective, operationally simple, uses water as a safe, environmentally friendly solvent, and DABCO as a green base‐organocatalyst, and affords good to excellent yields of products.展开更多
This account gives an overview of our recent work in the area of conjugated azomethines derived from 2-aminothiophenes.It will be presented that mild reaction conditions can be used to selectively prepare symmetric an...This account gives an overview of our recent work in the area of conjugated azomethines derived from 2-aminothiophenes.It will be presented that mild reaction conditions can be used to selectively prepare symmetric and unsymmetric conjugated azomethines.It further will be demonstrated that azomethines consisting of various 5-membered aryl heterocycles lead to chemically,reductively,hydrolytically,and oxidatively robust compounds.The optical and electrochemical properties of these materials can be tuned contingent on the degree of conjugation,type of aryl heterocycle,and by including various electronic groups.The end result is materials having colors spanning 250 nm across the visible spectrum.These colors further can be tuned via electrochemical or chemical doping.The resulting doped states have high color contrasts from their corresponding neutral states.The collective opto-electronic properties and the means to readily tune them,make thiophenoazomethine derivatives interesting materials for potential use in a gamut of applications.展开更多
A series of small-molecular fluorescent probes based on nitrogen-fused pyridazinone scaffold were developed in this report.The design strategy involved two steps:1)enhancing the electron-withdrawing ability of the acc...A series of small-molecular fluorescent probes based on nitrogen-fused pyridazinone scaffold were developed in this report.The design strategy involved two steps:1)enhancing the electron-withdrawing ability of the acceptor by incorporating an N-heterocyclic aromatic ring(pyridine or pyrazine)at the C4 and C5 positions of the pyridazinone skeleton and 2)anchoring a triphenylphosphine or morpholine tail as the subcellular targeting group.These fluorescent probes displayed excellent properties in live cell and brain tissue imaging.展开更多
文摘The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads to substantial difficulty for chiral catalysts to provide sufficient enantiocontrol.Moreover,a racemic background process is often inevitable,further deteriorating enantioselectivity.In this regard,an effective protocol has been established for enantioselective intermolecular[2+2]photocycloadditions to overcome the challenges,which is capitalising on the ground-state preassociations of chiral catalysts with photoactivated substrates.Here,we report the viability of substrate-differentiating synergistic catalysis for this important reaction.In this new platform,energy transfer occurs between DPZ as a photosensitizer and enones or(E)-2-substituted vinylazaarenes for producing triplet-state species,and chiral phosphoric acid interacts with ground-state 2-vinylazaarenes via hydrogen bonding for subsequent enantiofacial cycloaddition.Although all active species are dispersed in the reaction system,valuable enantioenriched mono-and di-azaarene-functionalized cyclobutanes are obtained efficiently and selectively.In addition to constructing all-carbon quaternary stereocentres,flexible modulation of azaaryl groups and other substituents on the cyclobutane ring is also operative.
基金supported by the Research Council of Payame Noor University
文摘This report describes a new three‐component strategy for the regioselective synthesis of a series of tri‐substituted pyridazines via a 1,4‐diazabicyclo[2.2.2]octane （DABCO）‐catalyzed condensation of propiophenones, arylglyoxalmonohydrates and hydrazine hydrate in water. This method provides a green and convenient one‐pot route toward a diverse set of 3,6‐diaryl‐4‐methylpyridazines bearing various aryl substituents. This procedure is highly regioselective, operationally simple, uses water as a safe, environmentally friendly solvent, and DABCO as a green base‐organocatalyst, and affords good to excellent yields of products.
基金Financial support for the original publications was provided by NSERC Canada in the form of a Discovery Grant,Strategic Research Grants,Idea-to-Innovation and Research Tools and Instruments grants in additionto CFI for additional equipment funding
文摘This account gives an overview of our recent work in the area of conjugated azomethines derived from 2-aminothiophenes.It will be presented that mild reaction conditions can be used to selectively prepare symmetric and unsymmetric conjugated azomethines.It further will be demonstrated that azomethines consisting of various 5-membered aryl heterocycles lead to chemically,reductively,hydrolytically,and oxidatively robust compounds.The optical and electrochemical properties of these materials can be tuned contingent on the degree of conjugation,type of aryl heterocycle,and by including various electronic groups.The end result is materials having colors spanning 250 nm across the visible spectrum.These colors further can be tuned via electrochemical or chemical doping.The resulting doped states have high color contrasts from their corresponding neutral states.The collective opto-electronic properties and the means to readily tune them,make thiophenoazomethine derivatives interesting materials for potential use in a gamut of applications.
基金Beijing Natural Science Foundation(Grant No.7162110)Interdisciplinary Medicine Seed Fund of Peking University(Grant No.BMU2018MC004)the National Natural Science Foudation of China(Grant No.201807006,81872731,91630314)
文摘A series of small-molecular fluorescent probes based on nitrogen-fused pyridazinone scaffold were developed in this report.The design strategy involved two steps:1)enhancing the electron-withdrawing ability of the acceptor by incorporating an N-heterocyclic aromatic ring(pyridine or pyrazine)at the C4 and C5 positions of the pyridazinone skeleton and 2)anchoring a triphenylphosphine or morpholine tail as the subcellular targeting group.These fluorescent probes displayed excellent properties in live cell and brain tissue imaging.
