Sensory evaluation is an important way for evaluating the quality of tea.By sensory evaluation,we can judge and identify the quality,distinguish the types,and characterize unique qualities of dark tea,in order to offe...Sensory evaluation is an important way for evaluating the quality of tea.By sensory evaluation,we can judge and identify the quality,distinguish the types,and characterize unique qualities of dark tea,in order to offer technical guidance for producers and give references to consumers.In this paper,we mainly summarized the requirements and methods of dark tea evaluation,expounded the characteristics in main producing areas,and analyzed the key process characteristics and the main technology that affecting the quality formation of dark tea.展开更多
Palladium-catalyzed Mizoroki-Heck reaction is a powerful and efficient method for construction of Csp2–Csp2 bonds.Herein,four palladium complexes(I—IV)with N,O-bidentate ligands(L1—L4)based on N-oxide units from cy...Palladium-catalyzed Mizoroki-Heck reaction is a powerful and efficient method for construction of Csp2–Csp2 bonds.Herein,four palladium complexes(I—IV)with N,O-bidentate ligands(L1—L4)based on N-oxide units from cyclic secondary amines were easily synthesized and successfully applied in Mizoroki-Heck reaction of aryl bromides with electron-deficient olefins.X-ray diffraction analyses indicated the palladium(II)atom of II took the distorted square planar geometry and was four-coordinated by nitrogen and oxygen atoms from two ligands(L2).Two free chloride ions were presented as counter anions in complex II.But the palladium(II)center of IV was coordinated by nitrogen and oxygen atoms from one ligand(L4)as well as two chlorine atoms,which exhibited the nearly square-planar geometry.The study on catalytic properties of palladium complexes revealed that complex II exhibited high activity superior to the other complexes.The coupling reactions of a series of aryl bromides and olefin derivatives proceeded in the presence of 2—5 mol%palladium complex II,giving the desired products in good to excellent yields.The advantages of this method such as good compatibility of functional groups,high yields,and short reaction times made it more attractive for constructing Csp2–Csp2 bonds in the synthesis of functional molecules and materials.展开更多
文摘Sensory evaluation is an important way for evaluating the quality of tea.By sensory evaluation,we can judge and identify the quality,distinguish the types,and characterize unique qualities of dark tea,in order to offer technical guidance for producers and give references to consumers.In this paper,we mainly summarized the requirements and methods of dark tea evaluation,expounded the characteristics in main producing areas,and analyzed the key process characteristics and the main technology that affecting the quality formation of dark tea.
基金the Natural Science Foundation of Shanxi Province(No.201901D111276)Innovative Program of Graduate Education in Shanxi Province(No.2023KY464)for financial support ofthis work.
文摘Palladium-catalyzed Mizoroki-Heck reaction is a powerful and efficient method for construction of Csp2–Csp2 bonds.Herein,four palladium complexes(I—IV)with N,O-bidentate ligands(L1—L4)based on N-oxide units from cyclic secondary amines were easily synthesized and successfully applied in Mizoroki-Heck reaction of aryl bromides with electron-deficient olefins.X-ray diffraction analyses indicated the palladium(II)atom of II took the distorted square planar geometry and was four-coordinated by nitrogen and oxygen atoms from two ligands(L2).Two free chloride ions were presented as counter anions in complex II.But the palladium(II)center of IV was coordinated by nitrogen and oxygen atoms from one ligand(L4)as well as two chlorine atoms,which exhibited the nearly square-planar geometry.The study on catalytic properties of palladium complexes revealed that complex II exhibited high activity superior to the other complexes.The coupling reactions of a series of aryl bromides and olefin derivatives proceeded in the presence of 2—5 mol%palladium complex II,giving the desired products in good to excellent yields.The advantages of this method such as good compatibility of functional groups,high yields,and short reaction times made it more attractive for constructing Csp2–Csp2 bonds in the synthesis of functional molecules and materials.
