The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study a...The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study aiming at the synthesis of multihydroxylated cephalostatin analogues, as for example cephalostatin 1Ⅰ, a potent anti-tumor natural product. Compound Ⅵ underwent chemo- and regioselective hydroboration reaction at only one of △14.15 double bonds furnishing compound Ⅸ as a major product in a fair yield.展开更多
In this work,an amino-modified cellulose nanofiber sponge was prepared and used as a support for polyoxometalate(POM)catalysts with a high loading efficiency.Fourier transform infrared spectroscopy,thermogravimetric a...In this work,an amino-modified cellulose nanofiber sponge was prepared and used as a support for polyoxometalate(POM)catalysts with a high loading efficiency.Fourier transform infrared spectroscopy,thermogravimetric analysis,and energy-dispersive X-ray spectroscopy revealed that an Anderson-type POM,(NH4)4[CuMo6O18(OH)6]·5H2O was successfully immobilized on the sponge based on electrostatic interactions.Morphological analysis indicated that the POM-loaded sponge retained its porous structure and that the POM was homogeneously distributed on the sponge walls.The POM-loaded sponge exhibited excellent mechanical properties by recovering 79.9%of its original thickness following a 60%compression strain.The POM-loaded sponge was found to effectively catalyze the hydroboration of phenylacetylenes,yielding excellent conversion and regioselectivity of up to 96%and 99%,respectively.Its catalytic activity remained unchanged after five reuse cycles.These findings represent a scalable strategy for immobilizing POMs on porous supports.展开更多
Selective reduction of readily available N-heteroarenes is important in both organic synthesis and chemical biology.Herein,we describe ligand-controlled regiodivergent hydroboration of quinolines using well-defined am...Selective reduction of readily available N-heteroarenes is important in both organic synthesis and chemical biology.Herein,we describe ligand-controlled regiodivergent hydroboration of quinolines using well-defined amido-manganese catalysts,with an emphasis on the rarely reported 1,4-regioselectivity.Mechanistic studies showed that 1,2-hydroboration of quinoline was kinetically favorable and reversible,whereas 1,4-hydroboration was under thermodynamic control.Using a 1-methyimidazolebased pincer amido-manganese complex as the catalyst,cooperative C-H…N andπ…πnoncovalent interactions between the 1-methyimidazole moiety and quinoline substrates enabled kinetic accessibility of 1,4-hydroboration,giving thermodynamically favored 1,4-hydroborated quinolines as the major products.On this basis,Mn-catalyzed 1,4-hydroboration of a series of substituted quinolines proceeded smoothly in high yields.A high turnover number of 2500 was achieved in this reaction with satisfying regioselectivity.This transformation could be further applied to the C3-selective functionalization of quinolines,highlighting the synthetic utility of this methodology.In contrast,using a pyridine-based pincer amido-manganese complex as the catalyst,which lacked the C-H…N interaction,the free-energy barrier for 1,4-hydroboration significantly increased through a N-B…N interaction between the“HMn-NB”species and quinoline,resulting in the kinetically favored 1,2-hydroboration product with excellent regioselectivity.展开更多
We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of ...We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds.Both 1 and 2 react with HBpin by adding the B-H bond across the Ni-X bond (X=O or N),giving rise to the 18-electron Ni(II)-H active species,[H1(Bpin)]and[H_(2)(Bpin)].Subtle tuning of the Ni-X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R_(2)PC_(6)H_(4)X).Unlike[H_(2)(Bpin)],the activation of HBpin in[H1(Bpin)]is reversible,which enables the Ni-O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes,and as well as ketones and imines.展开更多
An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis(pinacolato)diboron was developed, affording b-vinylboronates as the only products in high yields. Extra hydrogen sources ...An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis(pinacolato)diboron was developed, affording b-vinylboronates as the only products in high yields. Extra hydrogen sources such as methanol are not needed in this catalytic system. This reaction could be performed successfully under ligand- and base-free conditions. It demonstrated that phenylpropiolic acids can be employed as alkyne synthons in the hydroboration reaction and exhibited good reactivity and higher selectivity than terminal alkynes.展开更多
The synthesis of bo rylated orga nofluorines is of great interest due to their potential values as synthons in modular construction of fluorine-containing molecules.Reported herein is a rhodium-catalyzed hydrobo ratio...The synthesis of bo rylated orga nofluorines is of great interest due to their potential values as synthons in modular construction of fluorine-containing molecules.Reported herein is a rhodium-catalyzed hydrobo ration of arylgem-difluoroalkenes leading to a series of α-difluoromethylated benzylborons.The use of cationic rhodium catalyst and a biphosphine ligand with large bite angle was crucial for reactivity by offering good regioselectivity and diminishing the undesired β-F elimination.Preliminary derivatizations of the products were conducted to showcase the utility of this protocol.展开更多
Regiodivergent 1,2-hydroboration of 1,3-dienes with pinacolborane has been accomplished by well-defined cobalt complexes of different bidentate ligands. The iminopyridine-cobalt system is selective for Markovnikov 1,2...Regiodivergent 1,2-hydroboration of 1,3-dienes with pinacolborane has been accomplished by well-defined cobalt complexes of different bidentate ligands. The iminopyridine-cobalt system is selective for Markovnikov 1,2-hydroboration to form allylboronates, while the FOXAP-cobalt(FOXAP=(S)-1-(diphenylphosphino)-2-[(S)-4-isopropyloxazolin-2-yl]ferrocene) catalyst effects the complementary anti-Markonikv 1,2-hydroboration to afford homoallyboronates with high regioselectivity.展开更多
We have previously reported that the Ti complex generated from Cp2TiCl2 and LiBH4 serves as a catalyst for hydroboration of alkenes. Sodium borohydride can also be utilized as a reagent for hydroboration if reaction i...We have previously reported that the Ti complex generated from Cp2TiCl2 and LiBH4 serves as a catalyst for hydroboration of alkenes. Sodium borohydride can also be utilized as a reagent for hydroboration if reaction is carried out in the pre-展开更多
The strong oxophilicity of actinide complexes prevents their applications in the transformation of oxygen-containing substrates.Herein,we report the use of a uranium(Ⅳ)alkyl complex as a catalyst for the hydroboratio...The strong oxophilicity of actinide complexes prevents their applications in the transformation of oxygen-containing substrates.Herein,we report the use of a uranium(Ⅳ)alkyl complex as a catalyst for the hydroboration of carbonyl compounds.This reaction has good functional group tolerance and chemo-selectivity under mild conditions.This study represents the rare example of catalytic reaction promoted by a uranium alkyl complex and highlights the potential of uranium complexes in synthetic chemistry.展开更多
The trans-hydroboration of alkyne represents a challenging task in organic synthesis.Reported herein is an Et2 Zn promotedβ-trans hydroboration of ynamides by using N-heterocyclic carbene(NHC)-ligated borane as boryl...The trans-hydroboration of alkyne represents a challenging task in organic synthesis.Reported herein is an Et2 Zn promotedβ-trans hydroboration of ynamides by using N-heterocyclic carbene(NHC)-ligated borane as boryl source.The reaction leads to a stereoselective construction of enamides bearing a valuable boryl substituent.Both aromatic and aliphatic ynamides were applicable to the reaction.Synthetic transformation of the C-B bond in the product via Suzuki-Miyaura coupling provides a simple and stereospecific route to multi-substituted enamides.Mechanistic studies were conducted and the possible mechanism was discussed.展开更多
Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction...Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C_(6)F_(5))_(3) in an frustrated Lewis pairs manner.A broad range of alkenes including stilbenes,β-methylstyrenes,styrenes,and alkyl-alkenes were suitable substrates for the B(C_(6)F_(5))_(3)-catalyzed hydroboration to furnish the desired products in good to high yields.Significantly,excellent regioselectivities were obtained in some cases.Mechanistic studies indicate that the B-H bond cleavage is likely involved in the rate-determining step.In addition,an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated.The current work provides a promising method for the activation of stable borane adducts,which might lead to some interesting transformations in the future.展开更多
The sustainable development of synthetic reactions catalyzed by earth-abundant metals is one of the principal goals in homogeneous catalysis.However,so far most of the protocols are still plagued by sophisticated liga...The sustainable development of synthetic reactions catalyzed by earth-abundant metals is one of the principal goals in homogeneous catalysis.However,so far most of the protocols are still plagued by sophisticated ligands,hazardous activators,high catalyst loading(1—10 mol%)and/or multistep synthesis of the metal complexes in the process development.Consequently,the development of earth-abundant metal catalysts with high activity from commercially available metal salts is highly desirable for practical utilization of base metal catalyzed synthetic methodology.Herein,we report the catalyst generated in situ from a mixture of catalytic amounts of Ni(acac)_(2)(as low as 0.005 mol%)and CsF,which is found highly active for Markovnikov-selective hydroboration of vinylarenes,including 1,1-disubstituted vinylarenes and internal olefins,affording a wide range of secondary and tertiary alkyl boronates in excellent yields.Mechanistic experiments indicate that the key to the success of this catalysis is the use of CsF,which in combination with pinacolborane acts as an effective activator for Ni(acac)_(2),probably generating metastable Ni nanoparticles in situ that demonstrate high activity in the catalytic hydroboration(TON up to 18800).展开更多
Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical struc...Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.展开更多
It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/s...It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/soft acid/base(HSAB)theory to selective reduction of quinoline and achieve a series of C3-functionalized tetrahydroquinoline in high to excellent yields(up to 99%)under mild conditions with the catalysis of B(C_(6)F_(5))_(3).A series of in situ NMR reactions are also performed to investigate this cascade reaction.Moreover,AB type monomer 6-(dimethylsilyl)quinoline and AA/BB type monomer 6,6'-biquinoline are synthesized for polymer synthesis,which represents the first example of silicon bridged polytetrahydroquinoline.展开更多
A new class of iron(II) hydrides based on a tetradentate PSNP ligand were synthesized and fully characterized. All the iron(II) complexes feature a folded PSNP ligand with cis reactive sites. The hydrido iron comp...A new class of iron(II) hydrides based on a tetradentate PSNP ligand were synthesized and fully characterized. All the iron(II) complexes feature a folded PSNP ligand with cis reactive sites. The hydrido iron complex [2 H(NCMe[2_TD$IF]1)](BF4) is capable of catalyzing aldehyde hydroboration by pinacolborane(HBpin) and with extremely high efficiency at room temperature. Aldehydes with various functional groups are compatible.展开更多
Development of low-resistance electrode/electrolyte interfaces is key for enabling all-solid-state batteries with fast-charging capabilities.Low interfacial resistance and high current density were demonstrated for Na...Development of low-resistance electrode/electrolyte interfaces is key for enabling all-solid-state batteries with fast-charging capabilities.Low interfacial resistance and high current density were demonstrated for Na-β″-alumina/sodium metal interfaces,making Na-β″-alumina a promising solid electrolyte for high-energy all-solid-state batteries.However,integration of Na-β″-alumina with a high-energy sodium-ion intercalation cathode remains challenging.Here,we report a proof-of-concept study that targets the implementation of a Na-β″-alumina ceramic electrolyte with a slurry-casted porous NaCrO_(2) cathode with infiltrated sodium hydroborates as secondary electrolyte.The hydroborate Na4(B_(12)H_(12))(B_(10)H_(10))possesses similar sodium-ion conductivity of 1 mS cm^(-1) at room temperature as Na-β″-alumina and can be fully densified by cold pressing.Using the Na4(B_(12)H_(12))(B_(10)H_(10))secondary electrolyte as interlayer between Na-β″-alumina and NaCrO_(2),we obtain a cathode-electrolyte interfacial resistance of only 25Ωcm^(2) after cold pressing at 70 MPa.Proof-of-concept cells with a sodium metal anode and a NaCrO_(2) cathode feature an initial discharge capacity of 103 mAh g^(-1) at C/10 and 42 mAh g^(-1) at 1 C with an excellent capacity retention of 88%after 100 cycles at 1 C at room temperature.Ion-milled cross-sections of the cathode/electrolyte interface demonstrate that intimate contact is maintained during cycling,proving that the use of hydroborates as secondary electrolyte and as an interlayer is a promising approach for the development of all-solid-state batteries with ceramic electrolytes.展开更多
The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framewor...The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framework and has been utilized as an important toolbox due to their structural stability.Herein,we design and synthesize[2.2]paracyclophane-derived oxazole-pyrimidine ligands(abberviated as PYMCOX).These N,N-ligands with stable properties,rigid structure and large steric hindrance performed successfully in nickel-catalyzed asymmetric 1,2-reduction ofα,β-unsaturated ketones,affording the chiral allylic alcohols with up to 99%yield and 99%ee.Meanwhile,this reduction reaction could be conducted on gram-scale without loss of activity and enantioselectivity,and the chiral ligand could be conveniently recovered with high yield.展开更多
文摘The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study aiming at the synthesis of multihydroxylated cephalostatin analogues, as for example cephalostatin 1Ⅰ, a potent anti-tumor natural product. Compound Ⅵ underwent chemo- and regioselective hydroboration reaction at only one of △14.15 double bonds furnishing compound Ⅸ as a major product in a fair yield.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.2232018A3-04,No.2232018-02,and No.2232018G-043)the Program of Introducing Talents of Discipline to Universities(No.105-07-005735)
文摘In this work,an amino-modified cellulose nanofiber sponge was prepared and used as a support for polyoxometalate(POM)catalysts with a high loading efficiency.Fourier transform infrared spectroscopy,thermogravimetric analysis,and energy-dispersive X-ray spectroscopy revealed that an Anderson-type POM,(NH4)4[CuMo6O18(OH)6]·5H2O was successfully immobilized on the sponge based on electrostatic interactions.Morphological analysis indicated that the POM-loaded sponge retained its porous structure and that the POM was homogeneously distributed on the sponge walls.The POM-loaded sponge exhibited excellent mechanical properties by recovering 79.9%of its original thickness following a 60%compression strain.The POM-loaded sponge was found to effectively catalyze the hydroboration of phenylacetylenes,yielding excellent conversion and regioselectivity of up to 96%and 99%,respectively.Its catalytic activity remained unchanged after five reuse cycles.These findings represent a scalable strategy for immobilizing POMs on porous supports.
基金the National Key R&D Program of China(grant no.2021YFF0701600)the National Natural Science Foundation of China(grant no.22225103)Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs,Shanghai Jiao Tong University,and the China Postdoctoral Science Foundation(grant nos.2020M680021 and 2021T140366),which was greatly appreciated.
文摘Selective reduction of readily available N-heteroarenes is important in both organic synthesis and chemical biology.Herein,we describe ligand-controlled regiodivergent hydroboration of quinolines using well-defined amido-manganese catalysts,with an emphasis on the rarely reported 1,4-regioselectivity.Mechanistic studies showed that 1,2-hydroboration of quinoline was kinetically favorable and reversible,whereas 1,4-hydroboration was under thermodynamic control.Using a 1-methyimidazolebased pincer amido-manganese complex as the catalyst,cooperative C-H…N andπ…πnoncovalent interactions between the 1-methyimidazole moiety and quinoline substrates enabled kinetic accessibility of 1,4-hydroboration,giving thermodynamically favored 1,4-hydroborated quinolines as the major products.On this basis,Mn-catalyzed 1,4-hydroboration of a series of substituted quinolines proceeded smoothly in high yields.A high turnover number of 2500 was achieved in this reaction with satisfying regioselectivity.This transformation could be further applied to the C3-selective functionalization of quinolines,highlighting the synthetic utility of this methodology.In contrast,using a pyridine-based pincer amido-manganese complex as the catalyst,which lacked the C-H…N interaction,the free-energy barrier for 1,4-hydroboration significantly increased through a N-B…N interaction between the“HMn-NB”species and quinoline,resulting in the kinetically favored 1,2-hydroboration product with excellent regioselectivity.
基金the financial support from the National Natural Science Foundation of China (Nos. 22022102 and 22071010)the financial support from China Postdoctoral Science Foundation (No. 2021M700462)。
文摘We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds.Both 1 and 2 react with HBpin by adding the B-H bond across the Ni-X bond (X=O or N),giving rise to the 18-electron Ni(II)-H active species,[H1(Bpin)]and[H_(2)(Bpin)].Subtle tuning of the Ni-X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R_(2)PC_(6)H_(4)X).Unlike[H_(2)(Bpin)],the activation of HBpin in[H1(Bpin)]is reversible,which enables the Ni-O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes,and as well as ketones and imines.
基金Financial support from the National Science Foundation of China (No. 21202049)the Recruitment Program of Global Experts (1000 Talents Plan)+2 种基金Fujian Hundred Talents PlanProgram of Innovative Research Team of Huaqiao UniversityInstrumental Analysis Center of Huaqiao University for analysis support
文摘An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis(pinacolato)diboron was developed, affording b-vinylboronates as the only products in high yields. Extra hydrogen sources such as methanol are not needed in this catalytic system. This reaction could be performed successfully under ligand- and base-free conditions. It demonstrated that phenylpropiolic acids can be employed as alkyne synthons in the hydroboration reaction and exhibited good reactivity and higher selectivity than terminal alkynes.
基金financial support from the National Natural Science Foundation of China(No.21971261)Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery(No.2019B030301005)+1 种基金Key Project of Chinese National Programs for Fundamental Research and Development(No.2016YFA0602900)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01Y093)is gratefully acknowledged。
文摘The synthesis of bo rylated orga nofluorines is of great interest due to their potential values as synthons in modular construction of fluorine-containing molecules.Reported herein is a rhodium-catalyzed hydrobo ration of arylgem-difluoroalkenes leading to a series of α-difluoromethylated benzylborons.The use of cationic rhodium catalyst and a biphosphine ligand with large bite angle was crucial for reactivity by offering good regioselectivity and diminishing the undesired β-F elimination.Preliminary derivatizations of the products were conducted to showcase the utility of this protocol.
基金supported by the National Key R&D Program of China (2016YFA0202900, 2015CB856600)the National Natural Science Foundation of China (21825109, 21432011, 21572255, 21732006)+1 种基金Chinese Academy of Sciences (XDB20000000, QYZDB-SSWSLH016)Science and Technology Commission Shanghai Municipality (17JC1401200)
文摘Regiodivergent 1,2-hydroboration of 1,3-dienes with pinacolborane has been accomplished by well-defined cobalt complexes of different bidentate ligands. The iminopyridine-cobalt system is selective for Markovnikov 1,2-hydroboration to form allylboronates, while the FOXAP-cobalt(FOXAP=(S)-1-(diphenylphosphino)-2-[(S)-4-isopropyloxazolin-2-yl]ferrocene) catalyst effects the complementary anti-Markonikv 1,2-hydroboration to afford homoallyboronates with high regioselectivity.
文摘We have previously reported that the Ti complex generated from Cp2TiCl2 and LiBH4 serves as a catalyst for hydroboration of alkenes. Sodium borohydride can also be utilized as a reagent for hydroboration if reaction is carried out in the pre-
基金supported by the National Natural Science Foundation of China(Grant No.91961116)the Fundamental Research Funds for the Central Universities,and Programs for high-level entrepreneurial and innovative talents introduction of Jiangsu Province。
文摘The strong oxophilicity of actinide complexes prevents their applications in the transformation of oxygen-containing substrates.Herein,we report the use of a uranium(Ⅳ)alkyl complex as a catalyst for the hydroboration of carbonyl compounds.This reaction has good functional group tolerance and chemo-selectivity under mild conditions.This study represents the rare example of catalytic reaction promoted by a uranium alkyl complex and highlights the potential of uranium complexes in synthetic chemistry.
基金Financial supports from the Key Project of Chinese National Programs for Fundamental Research and Development(No.2016YFA0602900)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01Y093)+1 种基金the Natural Science Foundation of China(No.81873071)the Pearl River S&T Nova Program of Guangzhou(No.201906010059)are gratefully acknowledged。
文摘The trans-hydroboration of alkyne represents a challenging task in organic synthesis.Reported herein is an Et2 Zn promotedβ-trans hydroboration of ynamides by using N-heterocyclic carbene(NHC)-ligated borane as boryl source.The reaction leads to a stereoselective construction of enamides bearing a valuable boryl substituent.Both aromatic and aliphatic ynamides were applicable to the reaction.Synthetic transformation of the C-B bond in the product via Suzuki-Miyaura coupling provides a simple and stereospecific route to multi-substituted enamides.Mechanistic studies were conducted and the possible mechanism was discussed.
基金the financial support from the National Natural Science Foundation of China(Nos.21871269 and 21521002).
文摘Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C_(6)F_(5))_(3) in an frustrated Lewis pairs manner.A broad range of alkenes including stilbenes,β-methylstyrenes,styrenes,and alkyl-alkenes were suitable substrates for the B(C_(6)F_(5))_(3)-catalyzed hydroboration to furnish the desired products in good to high yields.Significantly,excellent regioselectivities were obtained in some cases.Mechanistic studies indicate that the B-H bond cleavage is likely involved in the rate-determining step.In addition,an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated.The current work provides a promising method for the activation of stable borane adducts,which might lead to some interesting transformations in the future.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(No.21821002).
文摘The sustainable development of synthetic reactions catalyzed by earth-abundant metals is one of the principal goals in homogeneous catalysis.However,so far most of the protocols are still plagued by sophisticated ligands,hazardous activators,high catalyst loading(1—10 mol%)and/or multistep synthesis of the metal complexes in the process development.Consequently,the development of earth-abundant metal catalysts with high activity from commercially available metal salts is highly desirable for practical utilization of base metal catalyzed synthetic methodology.Herein,we report the catalyst generated in situ from a mixture of catalytic amounts of Ni(acac)_(2)(as low as 0.005 mol%)and CsF,which is found highly active for Markovnikov-selective hydroboration of vinylarenes,including 1,1-disubstituted vinylarenes and internal olefins,affording a wide range of secondary and tertiary alkyl boronates in excellent yields.Mechanistic experiments indicate that the key to the success of this catalysis is the use of CsF,which in combination with pinacolborane acts as an effective activator for Ni(acac)_(2),probably generating metastable Ni nanoparticles in situ that demonstrate high activity in the catalytic hydroboration(TON up to 18800).
基金support obtained from the Chinese Academy of Sciences(QYZDY-SSWSLH026 and XDB20020000)and the Drug Innovation Major Project(2018ZX09711001-005)is highly appreciated.The authors thank Zuming Lin for assisting with the experiments and Dr.Xiaoli Bao(SJTU)and Jie Sun(SIOC)for performing the X-ray analysis.
文摘Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.
基金supported by the National Natural Science Foundation of China(Grant Nos.21871107,22225104,21975102,22071077).
文摘It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/soft acid/base(HSAB)theory to selective reduction of quinoline and achieve a series of C3-functionalized tetrahydroquinoline in high to excellent yields(up to 99%)under mild conditions with the catalysis of B(C_(6)F_(5))_(3).A series of in situ NMR reactions are also performed to investigate this cascade reaction.Moreover,AB type monomer 6-(dimethylsilyl)quinoline and AA/BB type monomer 6,6'-biquinoline are synthesized for polymer synthesis,which represents the first example of silicon bridged polytetrahydroquinoline.
基金This work was supported by the National Key R&D Program of China(2018YFA0702003)the National Natural Science Foundation of China(21890383,21671117,21871159 and 21901135).
基金financial support from the "1000 Youth Talents Plan"the National Natural Science Foundation of China (Nos. 21402107, 91427303)the Natural Science Foundation of Shandong Province (Nos. ZR2014M011)
文摘A new class of iron(II) hydrides based on a tetradentate PSNP ligand were synthesized and fully characterized. All the iron(II) complexes feature a folded PSNP ligand with cis reactive sites. The hydrido iron complex [2 H(NCMe[2_TD$IF]1)](BF4) is capable of catalyzing aldehyde hydroboration by pinacolborane(HBpin) and with extremely high efficiency at room temperature. Aldehydes with various functional groups are compatible.
基金support from the BRIDGE Proof-of-Concept program under contract number 40B1-0_198678/2.
文摘Development of low-resistance electrode/electrolyte interfaces is key for enabling all-solid-state batteries with fast-charging capabilities.Low interfacial resistance and high current density were demonstrated for Na-β″-alumina/sodium metal interfaces,making Na-β″-alumina a promising solid electrolyte for high-energy all-solid-state batteries.However,integration of Na-β″-alumina with a high-energy sodium-ion intercalation cathode remains challenging.Here,we report a proof-of-concept study that targets the implementation of a Na-β″-alumina ceramic electrolyte with a slurry-casted porous NaCrO_(2) cathode with infiltrated sodium hydroborates as secondary electrolyte.The hydroborate Na4(B_(12)H_(12))(B_(10)H_(10))possesses similar sodium-ion conductivity of 1 mS cm^(-1) at room temperature as Na-β″-alumina and can be fully densified by cold pressing.Using the Na4(B_(12)H_(12))(B_(10)H_(10))secondary electrolyte as interlayer between Na-β″-alumina and NaCrO_(2),we obtain a cathode-electrolyte interfacial resistance of only 25Ωcm^(2) after cold pressing at 70 MPa.Proof-of-concept cells with a sodium metal anode and a NaCrO_(2) cathode feature an initial discharge capacity of 103 mAh g^(-1) at C/10 and 42 mAh g^(-1) at 1 C with an excellent capacity retention of 88%after 100 cycles at 1 C at room temperature.Ion-milled cross-sections of the cathode/electrolyte interface demonstrate that intimate contact is maintained during cycling,proving that the use of hydroborates as secondary electrolyte and as an interlayer is a promising approach for the development of all-solid-state batteries with ceramic electrolytes.
基金Financial support from National Natural Science Foundation of China (22171260)K.C.Wong Education Foundation of CAS (GJTD-2020-08)is acknowledged.
文摘The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framework and has been utilized as an important toolbox due to their structural stability.Herein,we design and synthesize[2.2]paracyclophane-derived oxazole-pyrimidine ligands(abberviated as PYMCOX).These N,N-ligands with stable properties,rigid structure and large steric hindrance performed successfully in nickel-catalyzed asymmetric 1,2-reduction ofα,β-unsaturated ketones,affording the chiral allylic alcohols with up to 99%yield and 99%ee.Meanwhile,this reduction reaction could be conducted on gram-scale without loss of activity and enantioselectivity,and the chiral ligand could be conveniently recovered with high yield.