Rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes are among the most powerful methods for C-C bond formation.For these transformations,subtle manipulation of ancillary ligands can lead to dramatic changes in ...Rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes are among the most powerful methods for C-C bond formation.For these transformations,subtle manipulation of ancillary ligands can lead to dramatic changes in reactivity and selectivity.However,detailed mechanistic studies concerning the ligand effects are rare.In this study,we investigated the origin of ligand-controlled product-selectivity in rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes,using a series of well-defined[CpXRhⅢ]complexes that feature electronically or sterically distinct Cp^(X)(Cp(η^(5)-C_(5)H_(5)),Cp^(CF3)(η^(5)-C_(5)Me_(4)CF_(3))and Cp^(∗)(η^(5)-C_(5)Me_(5)))ligands.A combination of experimental and theoretical investigations showed that(i)rhodium hydride species containing the electron rich Cp^(∗)ligand can undergo reinsertion of the alkene,thereby allowing rhodium-walking,(ii)rhodium hydride species involving the electron-deficient Cp or Cp^(CF3) ligands prefer reductive elimination rather than alkene insertion.These findings offer valuable insights on future rational catalyst design for selective arene-alkene cross coupling reactions.展开更多
Bacterial cellulose(BC)hydrogel spheroid plays a significant role in diverse fields due to its spatial 3D structure and properties.In the present work,a series of BC spheroids with controllable size and shape was obta...Bacterial cellulose(BC)hydrogel spheroid plays a significant role in diverse fields due to its spatial 3D structure and properties.In the present work,a series of BC spheroids with controllable size and shape was obtained via an in situ biosynthesis.Crucial factors for fabricating BC spheroid in-cluding inoculum concentration of 1.35×10^(3)CFU/mL,shaking speeds at 100 r/min,and 48-96 h incubation time during the biosynthetic process,were comprehensively established.An operable mechanism model for tuning the size of BC spheroids from 0.4 to 5.0 mm was proposed with a fresh feeding medium strategy of dynamic culture.The resulting BC spheroids exhibit an inter-active 3D network of nanofibers,a crystallinity index of 72.3%,a specific surface area of 91.2 m^(2)/g,and good cytocompatibility.This study reinforces the understanding of BC spheroid forma-tion and explores new horizons for the design of BC spheroids-derived functional matrix materials for medical care.展开更多
基金financial support from the National Natural Science Foundation of China(Nos.21772162,21772165,22171237,22071208)Youth Innovation foundation of Xiamen(No.3502Z20206058).
文摘Rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes are among the most powerful methods for C-C bond formation.For these transformations,subtle manipulation of ancillary ligands can lead to dramatic changes in reactivity and selectivity.However,detailed mechanistic studies concerning the ligand effects are rare.In this study,we investigated the origin of ligand-controlled product-selectivity in rhodium(Ⅲ)-catalyzed C-H couplings of arenes with alkenes,using a series of well-defined[CpXRhⅢ]complexes that feature electronically or sterically distinct Cp^(X)(Cp(η^(5)-C_(5)H_(5)),Cp^(CF3)(η^(5)-C_(5)Me_(4)CF_(3))and Cp^(∗)(η^(5)-C_(5)Me_(5)))ligands.A combination of experimental and theoretical investigations showed that(i)rhodium hydride species containing the electron rich Cp^(∗)ligand can undergo reinsertion of the alkene,thereby allowing rhodium-walking,(ii)rhodium hydride species involving the electron-deficient Cp or Cp^(CF3) ligands prefer reductive elimination rather than alkene insertion.These findings offer valuable insights on future rational catalyst design for selective arene-alkene cross coupling reactions.
基金support from National Natural Science Foundation of China (No.51803092,No.51873087)Fundamental Research Funds for the Central Universities (No.30920130121001)+1 种基金Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD,China)project funded by Jiangsu Funding Program for Excellent Postdoctoral Talent。
文摘Bacterial cellulose(BC)hydrogel spheroid plays a significant role in diverse fields due to its spatial 3D structure and properties.In the present work,a series of BC spheroids with controllable size and shape was obtained via an in situ biosynthesis.Crucial factors for fabricating BC spheroid in-cluding inoculum concentration of 1.35×10^(3)CFU/mL,shaking speeds at 100 r/min,and 48-96 h incubation time during the biosynthetic process,were comprehensively established.An operable mechanism model for tuning the size of BC spheroids from 0.4 to 5.0 mm was proposed with a fresh feeding medium strategy of dynamic culture.The resulting BC spheroids exhibit an inter-active 3D network of nanofibers,a crystallinity index of 72.3%,a specific surface area of 91.2 m^(2)/g,and good cytocompatibility.This study reinforces the understanding of BC spheroid forma-tion and explores new horizons for the design of BC spheroids-derived functional matrix materials for medical care.