An efficient magnesium bistrifluoromethanesulfonimide[Mg（NTf_2）_2]catalyzed hydroalkylation of aromatic olefins with 1,3- diketones under solvent-free conditions has been developed.The reactions proceed smoothly to ...An efficient magnesium bistrifluoromethanesulfonimide[Mg（NTf_2）_2]catalyzed hydroalkylation of aromatic olefins with 1,3- diketones under solvent-free conditions has been developed.The reactions proceed smoothly to give the desired products in good yields in short reaction times.展开更多
Pyridinium bromochromate has been found to be a highly efficient and selective reagent for the α-monobromination of 1,3- diketones and β-keto-esters in the absence of base, Lewis acid, or other catalyst. The product...Pyridinium bromochromate has been found to be a highly efficient and selective reagent for the α-monobromination of 1,3- diketones and β-keto-esters in the absence of base, Lewis acid, or other catalyst. The products were formed in high to excellent yields under mild reaction conditions and in short reaction times.展开更多
For the metal-catalyzed asymmetric hydrogenation of α-substituted ketones,cis reductive products are generally obtained due to steric hindrance of substituents.Herein,an unprecedented trans reductive products were ob...For the metal-catalyzed asymmetric hydrogenation of α-substituted ketones,cis reductive products are generally obtained due to steric hindrance of substituents.Herein,an unprecedented trans reductive products were observed in palladium-catalyzed hydrogenative desymmetrization of cyclic and acyclic 1,3-diketones,providing the chiral trans β-hydroxy ketones with two adjacent stereocenters including one α-tertiary or quaternary stereocenter with high enantioselectivity and diastereoselectivity.Mechanistic studies and DFT calculations suggested that the rarely observed diastereoselectivity reversal is ascribed to the charge-charge interaction between the palladium and aromatic ring of the substrate,which could not only result in the reversal of the diastereoselectivity,but also improve the reactivity.展开更多
Ethyl 4,4,4-trifluoro-3-oxo-butyrate reacted with 2,6-dimethyl-3,5-diacetyl-pyridine 1 in the presence of NaOC2H5 at 0 ℃ to give 2,6-dimethyl-3,5-bis（4,4,4-trifluoro-1,3-oxo-butyl）-pyridine （2a） in good yield. Cy...Ethyl 4,4,4-trifluoro-3-oxo-butyrate reacted with 2,6-dimethyl-3,5-diacetyl-pyridine 1 in the presence of NaOC2H5 at 0 ℃ to give 2,6-dimethyl-3,5-bis（4,4,4-trifluoro-1,3-oxo-butyl）-pyridine （2a） in good yield. Cyclization reaction of 2a and aryl imidoyl chlorides 5a--5i, obtained from chlorination of aryl oximes with N-chlorosuccimide, afforded 2,6-dimethyl-3,5-bis[（3-aryl-5-trifluoromethyl）-isoxazol-4-carbonyl]-pyridine derivatives 6a=6i.展开更多
An efficient protocol for the synthesis of asymmetric 1,3-diketones was reported through diacylation of1,1-diborylalkanes using two different acyl sources.In this transfo rmation,an enolate boron species was initially...An efficient protocol for the synthesis of asymmetric 1,3-diketones was reported through diacylation of1,1-diborylalkanes using two different acyl sources.In this transfo rmation,an enolate boron species was initially formed by introducing an acyl group,then it was trapped by another acyl group to form 1,3-diketone.This method not only provided the gateway to obtain a series of 1,3-diketones,but also afforded an operationally simple and efficient access to pyrazoles and isoxazoles.展开更多
The clarification of the critical operating conditions and the failure mechanism of superlubricity systems is of great significance for seeking appropriate applications in industry.In this work,the superlubricity regi...The clarification of the critical operating conditions and the failure mechanism of superlubricity systems is of great significance for seeking appropriate applications in industry.In this work,the superlubricity region of 1,3-diketone oil EPND(1-(4-ethyl phenyl)nonane-1,3-dione)on steel surfaces was identified by performing a series of ball-on-disk rotation friction tests under various normal loads(3.5–64 N)and sliding velocities(100–600 mm/s).The result shows that beyond certain loads or velocities superlubricity failed to be reached due to the following negative effects:(1)Under low load(≤3.5 N),insufficient running-in could not ensure good asperity level conformity between the upper and lower surfaces;(2)the high load(≥64 N)produced excessive wear and big debris;(3)at low velocity(≤100 mm/s),the weak hydrodynamic effect and the generated debris deteriorated the lubrication performance;(4)at high velocity(≥500 mm/s),oil migration occurred and resulted in oil starvation.In order to expand the load and velocity boundaries of the superlubricity region,an optimized running-in method was proposed to avoid the above negative effects.By initially operating a running-in process under a suitable combination of load and velocity(e.g.16 N and 300 mm/s)and then switching to the target certain higher or lower load/velocity(e.g.100 N),the superlubricity region could break through its original boundaries.The result of this work suggests that oil-based superlubricity of 1,3-diketone is a promising solution to friction reduction under suitable operating conditions especially using a well-designed running-in strategy.展开更多
A novel anionic trinuclear linear copper（II） complex {[Et3NH][Cul.5（CH3COO）- （TTA）3] } 2 （1, TTA = 2-thenoyltrifluoroacetonate） has been synthesized in a direct reaction involving copper（]l） acetate monohydr...A novel anionic trinuclear linear copper（II） complex {[Et3NH][Cul.5（CH3COO）- （TTA）3] } 2 （1, TTA = 2-thenoyltrifluoroacetonate） has been synthesized in a direct reaction involving copper（]l） acetate monohydrate, TTA and excess triethylamine base in dichloromethane solvent. Green colored X-ray quality crystals of 1 were grown from n-hexane solvent at room temperature. The data were collected at 100 K. Compound I crystallizes in the monoclinic P21/n space group （a = 11.2141（8）, b = 19.0965（13）, c = 17.3680（14） A, β = 90.225（2）°, V= 3719.3（5） A3, Mr = 1840.14, Dc = 1.643 Mg/m3, F（000） = 1866, μ = 1.129 mm^-1 and Z = 2）. The asymmetric unit of 1 contains two copper atoms, one of which lies on a crystallographic inversion center with 50% occupancy.展开更多
基金financially supported by the Special Scientific Research Project of Shaanxi Education Commission (Nos.09JK332,2010JS069)the Science Research Foundation of Baoji University of Arts and Sciences(No. ZK1053)
文摘An efficient magnesium bistrifluoromethanesulfonimide[Mg（NTf_2）_2]catalyzed hydroalkylation of aromatic olefins with 1,3- diketones under solvent-free conditions has been developed.The reactions proceed smoothly to give the desired products in good yields in short reaction times.
基金support from the Research Council of Mazandaran University
文摘Pyridinium bromochromate has been found to be a highly efficient and selective reagent for the α-monobromination of 1,3- diketones and β-keto-esters in the absence of base, Lewis acid, or other catalyst. The products were formed in high to excellent yields under mild reaction conditions and in short reaction times.
基金supported by the National Natural Science Foundation of China(21871255,21532006,21873096)Chinese Academy of Sciences(XDB17020300,XDB17010200)
文摘For the metal-catalyzed asymmetric hydrogenation of α-substituted ketones,cis reductive products are generally obtained due to steric hindrance of substituents.Herein,an unprecedented trans reductive products were observed in palladium-catalyzed hydrogenative desymmetrization of cyclic and acyclic 1,3-diketones,providing the chiral trans β-hydroxy ketones with two adjacent stereocenters including one α-tertiary or quaternary stereocenter with high enantioselectivity and diastereoselectivity.Mechanistic studies and DFT calculations suggested that the rarely observed diastereoselectivity reversal is ascribed to the charge-charge interaction between the palladium and aromatic ring of the substrate,which could not only result in the reversal of the diastereoselectivity,but also improve the reactivity.
基金Acknowledgement The authors thank the National Natural Science Foundation of China （NNSFC） （Nos. 21072128, 21272153）, the Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry for financial support.
文摘Ethyl 4,4,4-trifluoro-3-oxo-butyrate reacted with 2,6-dimethyl-3,5-diacetyl-pyridine 1 in the presence of NaOC2H5 at 0 ℃ to give 2,6-dimethyl-3,5-bis（4,4,4-trifluoro-1,3-oxo-butyl）-pyridine （2a） in good yield. Cyclization reaction of 2a and aryl imidoyl chlorides 5a--5i, obtained from chlorination of aryl oximes with N-chlorosuccimide, afforded 2,6-dimethyl-3,5-bis[（3-aryl-5-trifluoromethyl）-isoxazol-4-carbonyl]-pyridine derivatives 6a=6i.
基金the National Natural Science Foundation of China(Nos.91745110,21673261,21603245,21703265,21872156,21802150,21773210 and 21603190)Natural Science Foundation of Jiangsu Province(Nos.BK20190002,BK20181194 and BK20180247)+1 种基金Support from the Young Elite Scientist Sponsorship Program by CAST(No.YESS20170217)the Youth Innovation Promotion Association CAS(No.2018458)。
文摘An efficient protocol for the synthesis of asymmetric 1,3-diketones was reported through diacylation of1,1-diborylalkanes using two different acyl sources.In this transfo rmation,an enolate boron species was initially formed by introducing an acyl group,then it was trapped by another acyl group to form 1,3-diketone.This method not only provided the gateway to obtain a series of 1,3-diketones,but also afforded an operationally simple and efficient access to pyrazoles and isoxazoles.
基金supported by the National Natural Science Foundation of China(No.51975437)the Sino-German Center for Research Promotion(SGC)(GZ 1576).
文摘The clarification of the critical operating conditions and the failure mechanism of superlubricity systems is of great significance for seeking appropriate applications in industry.In this work,the superlubricity region of 1,3-diketone oil EPND(1-(4-ethyl phenyl)nonane-1,3-dione)on steel surfaces was identified by performing a series of ball-on-disk rotation friction tests under various normal loads(3.5–64 N)and sliding velocities(100–600 mm/s).The result shows that beyond certain loads or velocities superlubricity failed to be reached due to the following negative effects:(1)Under low load(≤3.5 N),insufficient running-in could not ensure good asperity level conformity between the upper and lower surfaces;(2)the high load(≥64 N)produced excessive wear and big debris;(3)at low velocity(≤100 mm/s),the weak hydrodynamic effect and the generated debris deteriorated the lubrication performance;(4)at high velocity(≥500 mm/s),oil migration occurred and resulted in oil starvation.In order to expand the load and velocity boundaries of the superlubricity region,an optimized running-in method was proposed to avoid the above negative effects.By initially operating a running-in process under a suitable combination of load and velocity(e.g.16 N and 300 mm/s)and then switching to the target certain higher or lower load/velocity(e.g.100 N),the superlubricity region could break through its original boundaries.The result of this work suggests that oil-based superlubricity of 1,3-diketone is a promising solution to friction reduction under suitable operating conditions especially using a well-designed running-in strategy.
基金Financial support:South African National Research Foundation,(SA-NRF/THRIP),University of the Free State Materials and Nanoscience Research Cluster,SASOL and PETLABS pharmaceuticals
文摘A novel anionic trinuclear linear copper（II） complex {[Et3NH][Cul.5（CH3COO）- （TTA）3] } 2 （1, TTA = 2-thenoyltrifluoroacetonate） has been synthesized in a direct reaction involving copper（]l） acetate monohydrate, TTA and excess triethylamine base in dichloromethane solvent. Green colored X-ray quality crystals of 1 were grown from n-hexane solvent at room temperature. The data were collected at 100 K. Compound I crystallizes in the monoclinic P21/n space group （a = 11.2141（8）, b = 19.0965（13）, c = 17.3680（14） A, β = 90.225（2）°, V= 3719.3（5） A3, Mr = 1840.14, Dc = 1.643 Mg/m3, F（000） = 1866, μ = 1.129 mm^-1 and Z = 2）. The asymmetric unit of 1 contains two copper atoms, one of which lies on a crystallographic inversion center with 50% occupancy.
