Spiro-cyclopropyl oxindoles are widely found in natural products and medicinal molecules.Herein,we report a highly stereo-and enantio–selective procedure for accessing this class of compounds via tertiary amine media...Spiro-cyclopropyl oxindoles are widely found in natural products and medicinal molecules.Herein,we report a highly stereo-and enantio–selective procedure for accessing this class of compounds via tertiary amine mediated cyclopropanation of ammonium ylides with the in-situ Heck reaction-generated 3-alkenyl indolones as the Michael receptors.This reaction features mild conditions,excellent enantioselectivity(up to 98%)and diastereoselectivity(up to 99:1),high atom-and step-economy,broad substrate scopes,and good functional group tolerance.Additionally,this scalable synthetic process could offer a novel strategy for the efficient synthesis of enantiopure spirocyclopropyl oxindoles.展开更多
This study presents a novel self-sensing steel fiber-reinforced polymer composite bar(SFCB).The SFCB combines damage control,self-sensing,and structural reinforcement functions using distributed fiber optic sensing(DF...This study presents a novel self-sensing steel fiber-reinforced polymer composite bar(SFCB).The SFCB combines damage control,self-sensing,and structural reinforcement functions using distributed fiber optic sensing(DFOS)technology.By combining DFOS strains with theoretical and numerical models,a multilevel performance method for damage assessment is proposed from the perspectives of safety,suitability,and durability.Stiffness is a metric used to assess the complete service history of the reinforced concrete(RC)structure,which was used to define the damage variables.Initially,a basic correlation is created between the SFCB strain and several performance characteristics,such as moment,curvature,load,deflection,stiffness,and crack breadth,at characteristic points.The threshold values of damage variables for safety,serviceability,and durability were determined based on loading peak,mid-span deflection limits,and crack width limits corresponding to the damage variables.Then,a modified fiber damage model based on DFOS strain data is proposed to improve identification,quantification,and tracking for fiber damage.Finally,the reliability of the proposed theoretical and numerical models was verified by three-point flexural tests of SFCB–RC beams,and the test beams were analyzed using the proposed method.The results show that increasing the reinforcement ratio can lower the threshold at all levels and improve the ability of the flexural beams to control damage.This study contributes to advancing the intelligence of RC structures and offers valuable insights for the design of intelligent RC structures.展开更多
In considerati on of the imports nee of n itrogen-contai ning heterocycles in both medicinal and material chemistry, herein, we intend to summarize the most recent advances about their synthesis by electrochemical deh...In considerati on of the imports nee of n itrogen-contai ning heterocycles in both medicinal and material chemistry, herein, we intend to summarize the most recent advances about their synthesis by electrochemical dehydrogenation.展开更多
文摘Spiro-cyclopropyl oxindoles are widely found in natural products and medicinal molecules.Herein,we report a highly stereo-and enantio–selective procedure for accessing this class of compounds via tertiary amine mediated cyclopropanation of ammonium ylides with the in-situ Heck reaction-generated 3-alkenyl indolones as the Michael receptors.This reaction features mild conditions,excellent enantioselectivity(up to 98%)and diastereoselectivity(up to 99:1),high atom-and step-economy,broad substrate scopes,and good functional group tolerance.Additionally,this scalable synthetic process could offer a novel strategy for the efficient synthesis of enantiopure spirocyclopropyl oxindoles.
基金financial support provided by the National Science Fund for Distinguished Young Scholars of China(52325804)the National Natural Science Foundation of China(U2001226 and 52108230)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(2022B1515120007)the Shenzhen Basic Research Project(JCYJ20210324095003010)。
文摘This study presents a novel self-sensing steel fiber-reinforced polymer composite bar(SFCB).The SFCB combines damage control,self-sensing,and structural reinforcement functions using distributed fiber optic sensing(DFOS)technology.By combining DFOS strains with theoretical and numerical models,a multilevel performance method for damage assessment is proposed from the perspectives of safety,suitability,and durability.Stiffness is a metric used to assess the complete service history of the reinforced concrete(RC)structure,which was used to define the damage variables.Initially,a basic correlation is created between the SFCB strain and several performance characteristics,such as moment,curvature,load,deflection,stiffness,and crack breadth,at characteristic points.The threshold values of damage variables for safety,serviceability,and durability were determined based on loading peak,mid-span deflection limits,and crack width limits corresponding to the damage variables.Then,a modified fiber damage model based on DFOS strain data is proposed to improve identification,quantification,and tracking for fiber damage.Finally,the reliability of the proposed theoretical and numerical models was verified by three-point flexural tests of SFCB–RC beams,and the test beams were analyzed using the proposed method.The results show that increasing the reinforcement ratio can lower the threshold at all levels and improve the ability of the flexural beams to control damage.This study contributes to advancing the intelligence of RC structures and offers valuable insights for the design of intelligent RC structures.
基金the National Natural Science Foundation of China(Grant No.21871234)Zhejiang Provincial Natural Science Foundation of China for Distinguished Young Scholars(Grant No.LR15H300001)+1 种基金the Zhejiang Provincial Thousand-Talent ProgramZhejiang University of Technology for financial support.
文摘In considerati on of the imports nee of n itrogen-contai ning heterocycles in both medicinal and material chemistry, herein, we intend to summarize the most recent advances about their synthesis by electrochemical dehydrogenation.
