The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and...The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and ten transition states,corresponding to different approach geometries have been located and characterized,The regioselectivity and stereoselectivity of the reactions are correctly predicted by the calculations and the reaction mechanisms are analyzed in terms of electronic and steric effects of the substitutents on the reacting ketene and cyc-lopentadiene.展开更多
An unexpected tricyclic compound 2,3,3a,4,5,9b-hexahydrophenylfuro[3.2-c] quinoline 4 and its aromatized product 6 were obtained when the cycloaddtion of imine 1 and substituted norbornene 2 was carried out in THF wit...An unexpected tricyclic compound 2,3,3a,4,5,9b-hexahydrophenylfuro[3.2-c] quinoline 4 and its aromatized product 6 were obtained when the cycloaddtion of imine 1 and substituted norbornene 2 was carried out in THF with a catalytic amount of boron trifluoride. The structures of the products were determined by spectral data and the mechanism of reaction was substantiated by the imitation reaction.展开更多
The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochem...The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochemical reactions have been investigated. The thermocycloadditions of 1a-1h are regiospecific in forming a novel heterobicyclic ring system. Exo-aryl-1-aza-7-oxabicyclo- [2.2.1]heptane.展开更多
Given the widespread applications of fluorinated substances in pharmaceuticals,biology,and materials,the development of fluorine-containing building blocks remains an important topic in organic chemistry.In the repert...Given the widespread applications of fluorinated substances in pharmaceuticals,biology,and materials,the development of fluorine-containing building blocks remains an important topic in organic chemistry.In the repertoire of fluorinated diazo compounds,research on tri-and difluorodiazoethane is well-established,but the lack of synthetic methods has left studies related to monofluorodiazoethane as an unexplored territory.In our current work,the taming of the smallest monofluorodiazoethane reagent was realized using two phenylsulfonyl mask groups.This newly synthesized diazo reagent displayed intriguing reactivity patterns:the reaction with aryldiazonium salts gave monofluoromethyl tetrazoles,whereas its reactivity with alkynes and alkenes furnished monofluoromethyl isoxazoles and dihydro-isoxazoles.Furthermore,the removal of the masking groups provided access to a wide range of monofluoromethyl-functionalized heterocycles.展开更多
The base mediated cycloaddition reactions of 4-dimethylamino-l-phenacylpyridinium bromides with two mo- lecular 3-phenaeylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl-3,3＇-bisoxin...The base mediated cycloaddition reactions of 4-dimethylamino-l-phenacylpyridinium bromides with two mo- lecular 3-phenaeylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl-3,3＇-bisoxin- doles in good yields and with high diastereoselectivity. The similar cycloaddition reactions of 1-（N,N-dialkylcarba- moylmethyl） and 1-cyanomethyl 4-dimethylamino-pyridinium bromide in refluxing ethanol in the presence of triethylamine a/so resulted in dispirocyclopentyl-3,3＇-bisoxindoles with high diastereoselectivity. The stereochemis- try of dispirocyclopentyl-3,3＇-bisoxindoles was elucidated on the basis of ^1H NMR data and single crystal struc- tures.展开更多
Mechanism of the cycloadditional formaldehyde has been investigated reaction between singlet with MP2/6-31G^＊ method, dichloro-germylidene and including geometry optimization, vibrational analysis and energies for t...Mechanism of the cycloadditional formaldehyde has been investigated reaction between singlet with MP2/6-31G^＊ method, dichloro-germylidene and including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cyeloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dominant reaction pathways, going with the formation of two side products （INT3 and INT4）, simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-traasfer product P2 via transition state TS2, with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.展开更多
Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two com...Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and inserted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation.The calculation results reveal that:(i)the insertion process of alkyne or carbon monoxide is the key step of the reaction;(ii)for the(5+2)cycloaddition reaction of acetylene,higher energy is required to break the Rh−O bond of the reactant,and the reaction tends to complete the insertion from the side of the Rh−C bond;(iii)for the(5+1)cycloaddition of carbon monoxide,both reaction paths have lower activation free energy,and the two will generate a competition mechanism.展开更多
The 1,3-dipolar cycloaddition reaction of dimethyl hex-2-en-4-ynedioate with azomethine ylides derived from reaction of L-proline with various isatins in methanol selectively resulted in the formation of functionalize...The 1,3-dipolar cycloaddition reaction of dimethyl hex-2-en-4-ynedioate with azomethine ylides derived from reaction of L-proline with various isatins in methanol selectively resulted in the formation of functionalized spiro[indoline-3,3’-pyrrolizine]acrylates as main products and spiro[indoline-3,3’-pyrrolizine]propiolates as minor products.This result indicated that the electron-deficient alkyne has higher reactivity than that of electron-deficient alkene in 1,3-dipolar cycloaddition reaction.展开更多
5-(1-Menthyloxy)-2(5-H)-furanone is used as s chiral dipolarophile for thermal asymmetric 1,3-dipolar cycloaddition reaction with C-phenyl-N-phenyl nitrone to give the diastereomerically pure cycloaddition product.
Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, ...Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, however, high temperature, high pressure, and high-purity CO_(2) are still required for the reaction.Here, we report two new Zn(Ⅱ) imidazolate frameworks incoporating MoO_(4)^(2–)or WO_(4)^(2–)units, which can catalyse cycloaddition of CO_(2) and epichlorohydrin at room temperature and atomospheric pressure, giving 95% yield after 24 h in pure CO_(2) and 98% yield after 48 h in simulated flue gas(15% CO_(2)+ 85% N_(2)),respectively. For comparison, the analogic Zn(Ⅱ) imidazolate framework MAF-6 without non-3d metal oxide units showed 71% and 33% yields under the same conditions, respectively. The insightful modulation mechanisms of the MoO_(4)^(2–)unit in optimizing the electronic structure of Zn(Ⅱ) centre, facilitating the rate-determined ring opening process, and minimizing the reaction activation energy, were revealed by X-ray photoelectron spectroscopy, temperature programmed desorption and computational calculations.展开更多
The cycloaddition reactions of methane and ethylene mediated by Ir^(+) have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations.Studies have shown that Ir^(+) ...The cycloaddition reactions of methane and ethylene mediated by Ir^(+) have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations.Studies have shown that Ir^(+) can mediate the cycloaddition reaction of CH4and two C_(2)H_(4) to generate a half-sandwich structure IrHCp^(+)(Cp=η^(5)-C_(5)H_(5))including pentamethylcyclopentadienyl ligand by continuous dehydrogenation reaction with the forming of three C-C bonds and seven C-H bonds.The orbital analysis indicates the mechanism of the cyclization reaction to generation of pentamethylcyclopentadienyl ligand with odd number carbon atom depends on the overlap ofπorbitals in-C_(2)H_(2) and carbene,which is more difficult than the forming of cyclobutadiene ligand and benzene.This study may help to understand the reaction mechanism in the cycloaddition reactions of organic compounds,which will be useful to guide the rational design of new catalysts with tailored selectivity and increased efficiency.展开更多
The 1.3-dipolar cycloaddition reaction of 2-trifluoromethyl- oxazolone and the activated carbon-carbon multiple bond was studied and gave a convenient way to synthesize 2-trifluoromethylpyrrole derivatives.
Lewis acid catalyzed cycloaddition reactions of N-arylideneaniline Ⅰ with 2,3-dihydrofuran Ⅱ gave a pair of epimers d1-2, 3, 3a, 4, 5, 9b-hexahydro-4-arylfuro [3,2-c]quinolines Ⅲ and Ⅲ) and a few of their correspo...Lewis acid catalyzed cycloaddition reactions of N-arylideneaniline Ⅰ with 2,3-dihydrofuran Ⅱ gave a pair of epimers d1-2, 3, 3a, 4, 5, 9b-hexahydro-4-arylfuro [3,2-c]quinolines Ⅲ and Ⅲ) and a few of their corresponding aromatized compounds Ⅳ.展开更多
Among the many strategies for CO_(2)resource utilization,the synthetic technology of cyclic carbonates with 100%atom economy through CO_(2)and epoxide is one of the most industrially viable routes,but its efficiency h...Among the many strategies for CO_(2)resource utilization,the synthetic technology of cyclic carbonates with 100%atom economy through CO_(2)and epoxide is one of the most industrially viable routes,but its efficiency has been severely hampered by the lack of highly active catalytic sites.Moreover,due to the intrinsic thermodynamic stability and kinetic inertia of CO_(2)and the higher energy barrier of the ring-opening reaction of epoxides,the heterogeneous catalytic conversion of CO_(2)highly depends on harsh operating conditions,high temperatures and pressures,and the incorporation of cocatalysts.The devel-opment of efficient heterogeneous catalysts for CO_(2)conversion under cocatalyst-free and mild conditions has always been a challenge.Herein,we have proposed a synergetic strategy of facet and vacancy engi-neering for the construction of highly efficient heterogeneous catalyst BiO1-x Br1-y-(010)for CO_(2)cycload-dition,where introducing the OVs-BrVs pairs into typical(010)facets BiOBr with simultaneous surface Lewis acid sites Bi^(3+)and nucleophilic sites Br^(−).By combining theoretical calculations and a series of systematic experiments,such as CO_(2)temperature-programmed desorption,electron paramagnetic res-onance and fluorescence probe analysis experiments,the introduced OVs-BrVs pair can not only form Bi^(3+)-Bi^(3-x)+dual active sites on the surface,which activate PO and CO_(2)respectively to reduce the energy barrier of CO_(2)insertion,but also activate Br^(−)near BrVs to enhance their nucleophilic attacking ability and reduce the energy barrier of epoxides ring-opening.As a result,the BiO1-x Br1-y-(010)with abundant surface OVs-BrVs pairs showed a high cyclic carbonates conversion of 99%with 100%selectivity un-der cocatalyst-free and mild conditions,far surpassing most heterogeneous catalytic systems.This work provides a completely new strategy to construct high-performance heterogeneous CO_(2)cycloaddition cata-lysts through a simple facet and vacancy engineering strategy to overcome the harsh operating conditions limitation and the use of cocatalysts.展开更多
The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a tw...The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a twisted four membered ring transition state.Two types of frontier orbital interactions are involved in this reaction.The activation barrier is calculated to be 123.1KJ/mol (MP2/3-21G result).展开更多
Nucleophilic chiral phosphine catalysis has been prosperous in asymmetric synthesis over the past two decades. Various tunable chiral phosphines display excellent activity and selectivity in asymmetric transformations...Nucleophilic chiral phosphine catalysis has been prosperous in asymmetric synthesis over the past two decades. Various tunable chiral phosphines display excellent activity and selectivity in asymmetric transformations including acycloaddition reactions and cycloaddition reactions. Enantiomerically enriched cyclic compounds are ubiquitous in natural products and drug molecules. These phosphinecatalyzed reactions provide effective and extensive strategies for the synthesis of a series of complex cyclic compounds as well as the synthesis of chiral compounds which could be easily transformed to carbocycles and heterocycles. This minireview summarizes recent developments in this area and highlights meaningful breakthroughs.展开更多
The crystal of the title compound C, C 30 H 30 N 2O 3S has been prepared by reaction of 1,5 benzothiazepine with N protected glycine and determined by X ray single crystal diffraction. Crystal data:...The crystal of the title compound C, C 30 H 30 N 2O 3S has been prepared by reaction of 1,5 benzothiazepine with N protected glycine and determined by X ray single crystal diffraction. Crystal data: M r =498.62, triclinic with P 1 space group, a=10.880(2), b=13.955(3), c=9.537(2), α=99.34(3)°, β=110.43(3)°, γ=88 56(3)°, V=1338.2(5) 3, F(000)=528, λ (Mo Kα)=0.71073, Z=2, D c =1 237g/cm 3, μ =0.154mm -1 . Final R=0.0453, wR =0.1256 for 3491 observed reflections 〔 I>2σ(I) 〕. Structure analysis reveals that the substituents at C(23) and C(7) in four membered ring are located on the same side. The conformation of seven membered ring is chair like.展开更多
文摘The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and ten transition states,corresponding to different approach geometries have been located and characterized,The regioselectivity and stereoselectivity of the reactions are correctly predicted by the calculations and the reaction mechanisms are analyzed in terms of electronic and steric effects of the substitutents on the reacting ketene and cyc-lopentadiene.
文摘An unexpected tricyclic compound 2,3,3a,4,5,9b-hexahydrophenylfuro[3.2-c] quinoline 4 and its aromatized product 6 were obtained when the cycloaddtion of imine 1 and substituted norbornene 2 was carried out in THF with a catalytic amount of boron trifluoride. The structures of the products were determined by spectral data and the mechanism of reaction was substantiated by the imitation reaction.
文摘The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochemical reactions have been investigated. The thermocycloadditions of 1a-1h are regiospecific in forming a novel heterobicyclic ring system. Exo-aryl-1-aza-7-oxabicyclo- [2.2.1]heptane.
基金financial support provided by the National Natural Science Foundation of China(NSFC,grant nos.92156025 and 22271212)the National Key Research and Development Program of China(grant nos.2019YFA0905100 and 2021YFF0701700)X.T.thanks the China Postdoctoral Science Foundation(grant no.2022M712350).
文摘Given the widespread applications of fluorinated substances in pharmaceuticals,biology,and materials,the development of fluorine-containing building blocks remains an important topic in organic chemistry.In the repertoire of fluorinated diazo compounds,research on tri-and difluorodiazoethane is well-established,but the lack of synthetic methods has left studies related to monofluorodiazoethane as an unexplored territory.In our current work,the taming of the smallest monofluorodiazoethane reagent was realized using two phenylsulfonyl mask groups.This newly synthesized diazo reagent displayed intriguing reactivity patterns:the reaction with aryldiazonium salts gave monofluoromethyl tetrazoles,whereas its reactivity with alkynes and alkenes furnished monofluoromethyl isoxazoles and dihydro-isoxazoles.Furthermore,the removal of the masking groups provided access to a wide range of monofluoromethyl-functionalized heterocycles.
文摘The base mediated cycloaddition reactions of 4-dimethylamino-l-phenacylpyridinium bromides with two mo- lecular 3-phenaeylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl-3,3＇-bisoxin- doles in good yields and with high diastereoselectivity. The similar cycloaddition reactions of 1-（N,N-dialkylcarba- moylmethyl） and 1-cyanomethyl 4-dimethylamino-pyridinium bromide in refluxing ethanol in the presence of triethylamine a/so resulted in dispirocyclopentyl-3,3＇-bisoxindoles with high diastereoselectivity. The stereochemis- try of dispirocyclopentyl-3,3＇-bisoxindoles was elucidated on the basis of ^1H NMR data and single crystal struc- tures.
文摘Mechanism of the cycloadditional formaldehyde has been investigated reaction between singlet with MP2/6-31G^＊ method, dichloro-germylidene and including geometry optimization, vibrational analysis and energies for the involved stationary points on the potential energy surface. From the potential energy profile, we predict that the cyeloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dominant reaction pathways, going with the formation of two side products （INT3 and INT4）, simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-traasfer product P2 via transition state TS2, with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.
基金This work was supported by the Natural Science Foundation of Gansu Province(20JR5RA479)the Outstanding Youth Research Program of Lanzhou University of Arts and Sciences(2018JCQN008).
文摘Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and inserted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation.The calculation results reveal that:(i)the insertion process of alkyne or carbon monoxide is the key step of the reaction;(ii)for the(5+2)cycloaddition reaction of acetylene,higher energy is required to break the Rh−O bond of the reactant,and the reaction tends to complete the insertion from the side of the Rh−C bond;(iii)for the(5+1)cycloaddition of carbon monoxide,both reaction paths have lower activation free energy,and the two will generate a competition mechanism.
基金financially supported by the National Natural Science Foundation of China(No.21572196)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘The 1,3-dipolar cycloaddition reaction of dimethyl hex-2-en-4-ynedioate with azomethine ylides derived from reaction of L-proline with various isatins in methanol selectively resulted in the formation of functionalized spiro[indoline-3,3’-pyrrolizine]acrylates as main products and spiro[indoline-3,3’-pyrrolizine]propiolates as minor products.This result indicated that the electron-deficient alkyne has higher reactivity than that of electron-deficient alkene in 1,3-dipolar cycloaddition reaction.
文摘5-(1-Menthyloxy)-2(5-H)-furanone is used as s chiral dipolarophile for thermal asymmetric 1,3-dipolar cycloaddition reaction with C-phenyl-N-phenyl nitrone to give the diastereomerically pure cycloaddition product.
基金supported by the National Natural Science Foundation of China (Nos. 22090061, 21731007, 21890380 and 22161021)the Guangdong Pearl River Talents Program (No. 2017BT01C161)the support of Jiangxi Province (No. jxsq2018106041)。
文摘Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, however, high temperature, high pressure, and high-purity CO_(2) are still required for the reaction.Here, we report two new Zn(Ⅱ) imidazolate frameworks incoporating MoO_(4)^(2–)or WO_(4)^(2–)units, which can catalyse cycloaddition of CO_(2) and epichlorohydrin at room temperature and atomospheric pressure, giving 95% yield after 24 h in pure CO_(2) and 98% yield after 48 h in simulated flue gas(15% CO_(2)+ 85% N_(2)),respectively. For comparison, the analogic Zn(Ⅱ) imidazolate framework MAF-6 without non-3d metal oxide units showed 71% and 33% yields under the same conditions, respectively. The insightful modulation mechanisms of the MoO_(4)^(2–)unit in optimizing the electronic structure of Zn(Ⅱ) centre, facilitating the rate-determined ring opening process, and minimizing the reaction activation energy, were revealed by X-ray photoelectron spectroscopy, temperature programmed desorption and computational calculations.
基金supported by Beijing Natural Science Foundation(No.2214064)the National Natural Science Foundation of China(Nos.21603037,21688102,92161115,21973016,91545122)the Fundamental Research Funds for the Central Universities(Nos.JB2015RCY03,JB2019MS052)supported by the fund of North China Electric Power University。
文摘The cycloaddition reactions of methane and ethylene mediated by Ir^(+) have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations.Studies have shown that Ir^(+) can mediate the cycloaddition reaction of CH4and two C_(2)H_(4) to generate a half-sandwich structure IrHCp^(+)(Cp=η^(5)-C_(5)H_(5))including pentamethylcyclopentadienyl ligand by continuous dehydrogenation reaction with the forming of three C-C bonds and seven C-H bonds.The orbital analysis indicates the mechanism of the cyclization reaction to generation of pentamethylcyclopentadienyl ligand with odd number carbon atom depends on the overlap ofπorbitals in-C_(2)H_(2) and carbene,which is more difficult than the forming of cyclobutadiene ligand and benzene.This study may help to understand the reaction mechanism in the cycloaddition reactions of organic compounds,which will be useful to guide the rational design of new catalysts with tailored selectivity and increased efficiency.
文摘The 1.3-dipolar cycloaddition reaction of 2-trifluoromethyl- oxazolone and the activated carbon-carbon multiple bond was studied and gave a convenient way to synthesize 2-trifluoromethylpyrrole derivatives.
文摘Lewis acid catalyzed cycloaddition reactions of N-arylideneaniline Ⅰ with 2,3-dihydrofuran Ⅱ gave a pair of epimers d1-2, 3, 3a, 4, 5, 9b-hexahydro-4-arylfuro [3,2-c]quinolines Ⅲ and Ⅲ) and a few of their corresponding aromatized compounds Ⅳ.
基金supported by the National Science Basic Research Program of Shaanxi(Nos.2024JC-YBQN-0103,2024JC-YBMS-127,2022JQ-102)the National Natural Science Foundation of China(No.52073228)the Xi’an Shiyou University Postgraduate Innovation and Practical Ability Training Project(No.YCS23213089).
文摘Among the many strategies for CO_(2)resource utilization,the synthetic technology of cyclic carbonates with 100%atom economy through CO_(2)and epoxide is one of the most industrially viable routes,but its efficiency has been severely hampered by the lack of highly active catalytic sites.Moreover,due to the intrinsic thermodynamic stability and kinetic inertia of CO_(2)and the higher energy barrier of the ring-opening reaction of epoxides,the heterogeneous catalytic conversion of CO_(2)highly depends on harsh operating conditions,high temperatures and pressures,and the incorporation of cocatalysts.The devel-opment of efficient heterogeneous catalysts for CO_(2)conversion under cocatalyst-free and mild conditions has always been a challenge.Herein,we have proposed a synergetic strategy of facet and vacancy engi-neering for the construction of highly efficient heterogeneous catalyst BiO1-x Br1-y-(010)for CO_(2)cycload-dition,where introducing the OVs-BrVs pairs into typical(010)facets BiOBr with simultaneous surface Lewis acid sites Bi^(3+)and nucleophilic sites Br^(−).By combining theoretical calculations and a series of systematic experiments,such as CO_(2)temperature-programmed desorption,electron paramagnetic res-onance and fluorescence probe analysis experiments,the introduced OVs-BrVs pair can not only form Bi^(3+)-Bi^(3-x)+dual active sites on the surface,which activate PO and CO_(2)respectively to reduce the energy barrier of CO_(2)insertion,but also activate Br^(−)near BrVs to enhance their nucleophilic attacking ability and reduce the energy barrier of epoxides ring-opening.As a result,the BiO1-x Br1-y-(010)with abundant surface OVs-BrVs pairs showed a high cyclic carbonates conversion of 99%with 100%selectivity un-der cocatalyst-free and mild conditions,far surpassing most heterogeneous catalytic systems.This work provides a completely new strategy to construct high-performance heterogeneous CO_(2)cycloaddition cata-lysts through a simple facet and vacancy engineering strategy to overcome the harsh operating conditions limitation and the use of cocatalysts.
基金This project is supported by Foundation of National Education Committee and Natural Science Fund of China
文摘The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a twisted four membered ring transition state.Two types of frontier orbital interactions are involved in this reaction.The activation barrier is calculated to be 123.1KJ/mol (MP2/3-21G result).
基金financial support from the National Basic Research Program of China(973 Project,No.2015CB856603)the National Natural Science Foundation of China(Nos.20472096,21372241,21361140350,20672127,21421091,21372250,21121062,21302203,20732008 and 21572052)
文摘Nucleophilic chiral phosphine catalysis has been prosperous in asymmetric synthesis over the past two decades. Various tunable chiral phosphines display excellent activity and selectivity in asymmetric transformations including acycloaddition reactions and cycloaddition reactions. Enantiomerically enriched cyclic compounds are ubiquitous in natural products and drug molecules. These phosphinecatalyzed reactions provide effective and extensive strategies for the synthesis of a series of complex cyclic compounds as well as the synthesis of chiral compounds which could be easily transformed to carbocycles and heterocycles. This minireview summarizes recent developments in this area and highlights meaningful breakthroughs.
文摘The crystal of the title compound C, C 30 H 30 N 2O 3S has been prepared by reaction of 1,5 benzothiazepine with N protected glycine and determined by X ray single crystal diffraction. Crystal data: M r =498.62, triclinic with P 1 space group, a=10.880(2), b=13.955(3), c=9.537(2), α=99.34(3)°, β=110.43(3)°, γ=88 56(3)°, V=1338.2(5) 3, F(000)=528, λ (Mo Kα)=0.71073, Z=2, D c =1 237g/cm 3, μ =0.154mm -1 . Final R=0.0453, wR =0.1256 for 3491 observed reflections 〔 I>2σ(I) 〕. Structure analysis reveals that the substituents at C(23) and C(7) in four membered ring are located on the same side. The conformation of seven membered ring is chair like.
