Allylic ethers are important functional motifs widespread in bioactive molecules and natural products and serve as versatile synthetic intermediates for value-added target molecules.Therefore,developing general and di...Allylic ethers are important functional motifs widespread in bioactive molecules and natural products and serve as versatile synthetic intermediates for value-added target molecules.Therefore,developing general and direct methods to allylic ethers from feedstocks is highly desirable.Direct cross-coupling of alkenes with free alcohols by allylic C-H functionalization under mild conditions represents the most ideal way for the synthesis of branched allylic ethers.Moreover,branch-selective allylic C-H oxygenation imposes additional challenge due to the increased steric hindrance.Herein,a dual catalysis of visible-light and cobaloxime enables allylic C-H direct oxygenation of styrenes with alcohols to afford branched allylic ethers has been developed.Notably,exclusive regio-and chemoselective mono-etherification of C-H bond to give branched allylic ethers with primary,secondary,and tertiary free alcohols.Moreover,other oxygen-based nucleophiles,such as carboxylate and cyclic 1,3-diketones,are also compatible in the reaction,providing a mild and robust allylic oxygenation of more steric hindered C-H from easily available alkenes.展开更多
Due to the complexity of compressible flows,nonlinear hydrodynamic stability theories in supersonic boundary layers are not sufficient.In order to reveal the nonlinear interaction mechanisms of the rapidly amplified 3...Due to the complexity of compressible flows,nonlinear hydrodynamic stability theories in supersonic boundary layers are not sufficient.In order to reveal the nonlinear interaction mechanisms of the rapidly amplified 3-D disturbances in supersonic boundary layers at high Mach numbers,the nonlinear evolutions of different disturbances in flat-plate boundary layers at Mach number 4.5,6 and 8 are analyzed by numerical simulations.It can be concluded that the 3-D disturbances are amplified rapidly when the amplitude of the 2-D disturbance reaches a certain level.The most rapidly amplified 3-D disturbances are Klebanoff type(K-type)disturbances which have the same frequency as the 2-D disturbance.Among these K-type 3-D disturbances,the disturbances located at the junction of upper branch and lower branch of the neutral curve are amplified higher.Through analyzing the relationship between the amplification rate and the spanwise wavenumber of the 3-D disturbances at different evolution stages,the mechanism of the spanwise wavenumber selectivity of K-type 3-D disturbances in the presence of a finite amplitude 2-D disturbance is explained.展开更多
基金Financial support from the National Natural Science Foundation of China(22171127,22371115,22401139)the Sichuan Science and Technology Program(2024ZYD0017)+4 种基金the Natural Science Foundation of Sichuan Province(2025ZNSFSC0128)the Shenzhen Science and Technology Innovation Committee(JCYJ20230807093522044,JCYJ20240813094226034)the Pearl River Talent Recruitment Program(2019QN01Y261)the Guangdong Provincial Key Laboratory of Catalysis(2020B121201002)is sincerely acknowledgedsupported by the SUSTech-NUS Joint Research Program。
文摘Allylic ethers are important functional motifs widespread in bioactive molecules and natural products and serve as versatile synthetic intermediates for value-added target molecules.Therefore,developing general and direct methods to allylic ethers from feedstocks is highly desirable.Direct cross-coupling of alkenes with free alcohols by allylic C-H functionalization under mild conditions represents the most ideal way for the synthesis of branched allylic ethers.Moreover,branch-selective allylic C-H oxygenation imposes additional challenge due to the increased steric hindrance.Herein,a dual catalysis of visible-light and cobaloxime enables allylic C-H direct oxygenation of styrenes with alcohols to afford branched allylic ethers has been developed.Notably,exclusive regio-and chemoselective mono-etherification of C-H bond to give branched allylic ethers with primary,secondary,and tertiary free alcohols.Moreover,other oxygen-based nucleophiles,such as carboxylate and cyclic 1,3-diketones,are also compatible in the reaction,providing a mild and robust allylic oxygenation of more steric hindered C-H from easily available alkenes.
基金supported by the State Key Program of National Natural Science Foundation of China(Grant No.11332007)
文摘Due to the complexity of compressible flows,nonlinear hydrodynamic stability theories in supersonic boundary layers are not sufficient.In order to reveal the nonlinear interaction mechanisms of the rapidly amplified 3-D disturbances in supersonic boundary layers at high Mach numbers,the nonlinear evolutions of different disturbances in flat-plate boundary layers at Mach number 4.5,6 and 8 are analyzed by numerical simulations.It can be concluded that the 3-D disturbances are amplified rapidly when the amplitude of the 2-D disturbance reaches a certain level.The most rapidly amplified 3-D disturbances are Klebanoff type(K-type)disturbances which have the same frequency as the 2-D disturbance.Among these K-type 3-D disturbances,the disturbances located at the junction of upper branch and lower branch of the neutral curve are amplified higher.Through analyzing the relationship between the amplification rate and the spanwise wavenumber of the 3-D disturbances at different evolution stages,the mechanism of the spanwise wavenumber selectivity of K-type 3-D disturbances in the presence of a finite amplitude 2-D disturbance is explained.
