A synergistic rhodium（Ⅱ）/phosphoric acid catalyzed three component reaction of 3-diazooxindoles,alcohols and N-benzhydryl-α-imino ester is developed for the efficient construction of chiral β-alkoxy C-β-tetrasub...A synergistic rhodium（Ⅱ）/phosphoric acid catalyzed three component reaction of 3-diazooxindoles,alcohols and N-benzhydryl-α-imino ester is developed for the efficient construction of chiral β-alkoxy C-β-tetrasubstituted α-amino acid derivatives in good yields and with excellent diastereoselectivities and high enantioselectivities.The synthetic application of the resulting products was illustrated by reducing with Pd/C under H_2 atmosphere followed reacting with CSCl_2 at room temperature to rapid afford 3-spirocyclic oxindole in a good yield with a chirality retainment.The three-component reaction is proposed to proceed through an electrophilic trapping of the oxonium ylides by N-benzhydryl-α-imino ester.展开更多
Enantioenrichedγ-butenolides constitute the structural core of many natural products and biologically active molecules,but their direct and atom-economical asymmetric assembly from simple starting materials remains q...Enantioenrichedγ-butenolides constitute the structural core of many natural products and biologically active molecules,but their direct and atom-economical asymmetric assembly from simple starting materials remains quite limited.Here,we describe a facile and atom-efficient synthesis of enantioenrichedα-aryl-γ-butenolides from cyclopropenyl carboxylic acid and electrondeficient olefins or isatins.The reaction proceeds via carboxylic acid insertion of carbenoid initiated by an achiral rhodium salt,followed by chiral Lewis acid-mediated enantioselective trapping of the resulting carboxylic oxonium ylides with enones and isatins.Various enantioenrichedγ-butenolides were obtained in high yields(up to 99%)with excellent stereoselectivities(up to>19:1 dr and up to 96%ee)under mild conditions by low catalyst loading(S/C=200).The potential application of these methods was demonstrated by the gram-scale synthesis ofγ-butenolides and their further transformations into other bioactive molecules.展开更多
We herein reported a sustainable synthesis of 3,3-disubstituted oxindoles via a Michael-type reaction based on the CuBr-catalysed capture of carboxylic oxonium ylides with isatylidene malononitrile.The reaction is cha...We herein reported a sustainable synthesis of 3,3-disubstituted oxindoles via a Michael-type reaction based on the CuBr-catalysed capture of carboxylic oxonium ylides with isatylidene malononitrile.The reaction is characterized by a high atom economy and low economic constraints.The catalyst CuBr could be conveniently recyclized.The products of the reaction were found to be inhibitory against Na ion channels.We expect the reaction to shed the light on synthesis of biologically interesting molecules directed by principles of green chemistry.展开更多
A chiral dirhodium complex is an effective and robust catalyst for asymmetric carbene transformations.However,dirhodiumcatalyzed asymmetric ylide interception processes are rare,mainly because of the dissociation of t...A chiral dirhodium complex is an effective and robust catalyst for asymmetric carbene transformations.However,dirhodiumcatalyzed asymmetric ylide interception processes are rare,mainly because of the dissociation of the metal catalyst before the stereo-determining step.Herein,we report a chiral dirhodium(Ⅱ)-catalyzed asymmetric annulation of vinyl diazoesters withα-hydroxyl ketones,which provides an efficient way to form chiral 2,3-dihydropyrans in good yields with excellent diastereoselectivities and enantioselectivities.This article is the first example of the chiral dirhodium complex–controlled asymmetric aldol-type interception of an in situ–formed oxonium ylide.The origin of the high stereoselectivity is well expounded via experimental and computational studies.These generated chiral products exhibit potent antiproliferation activity in three tested cancer cell lines,namely HCT116(colon cancer),A549(lung adenocarcinoma),and SJSA-1(osteosarcoma cancer).展开更多
Production o f aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for de...Production o f aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone （2-PAP）, was investigated over several ce-sium-exchanged polyoxometalate （Cs-POM） catalysts. Decomposition of 2-PAP can follow two dif-ferent mechanisms： an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox proper-ties of the catalysts. The catalysts of POMs perform the following functions： promoting active hy-drogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen libera-tion and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP （〉99%） with excellent selectivities to the desired products （98.6% for phenol and 91.1% for acetophenone） can be achieved.展开更多
The homogeneous system of 12-tungstophosphoric acid and diethylene glycol was studied using IR and NMR spectra. It was found that the protons in 12-tungstophosphoric acid formed proton oxonium ions with the hydroxyl o...The homogeneous system of 12-tungstophosphoric acid and diethylene glycol was studied using IR and NMR spectra. It was found that the protons in 12-tungstophosphoric acid formed proton oxonium ions with the hydroxyl oxygen in diethylene glycol by hydrogen-bonds, and the formed proton oxonium ions could react with the terminal oxygens of heteropoly anions. The dehydration-cyclization mechanism of diethylene glycol in the presence of heteropoly acid was also proposed.展开更多
The mechanisms of insertion of O-H bond of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2 C12. The formation of free alcoholic oxonium ylides...The mechanisms of insertion of O-H bond of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2 C12. The formation of free alcoholic oxonium ylides is found to be impossible. Alcoholic oxonium ylide are formed as the intermediates before beth the stepwise and the concerted transition states of insertion of O-H bend of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol. With re- gard to the mechanisms of insertion of O-H of Rh（ Ⅱ ） -methylene carbene into alcohols, analysis of the energy bartiers of the two mechanisms indicate that the stepwise mechanism is more plausible than the concerted mechanism.展开更多
基金NSFC (No. 21332003)STCSM (No. 15ZR1411000)Stake Key Laboratory of Advanced Technology for Materials Synthesis and Processing (2015-KF-11) for financial support
文摘A synergistic rhodium（Ⅱ）/phosphoric acid catalyzed three component reaction of 3-diazooxindoles,alcohols and N-benzhydryl-α-imino ester is developed for the efficient construction of chiral β-alkoxy C-β-tetrasubstituted α-amino acid derivatives in good yields and with excellent diastereoselectivities and high enantioselectivities.The synthetic application of the resulting products was illustrated by reducing with Pd/C under H_2 atmosphere followed reacting with CSCl_2 at room temperature to rapid afford 3-spirocyclic oxindole in a good yield with a chirality retainment.The three-component reaction is proposed to proceed through an electrophilic trapping of the oxonium ylides by N-benzhydryl-α-imino ester.
基金supported by the National Key R&D Program of China(2023YFA1506700)the National Natural Science Foundation of China(22271199,92256303)+1 种基金the Sichuan Science and Technology Program(2023YFSY0063)the Sichuan University(2020SCUNL204)。
文摘Enantioenrichedγ-butenolides constitute the structural core of many natural products and biologically active molecules,but their direct and atom-economical asymmetric assembly from simple starting materials remains quite limited.Here,we describe a facile and atom-efficient synthesis of enantioenrichedα-aryl-γ-butenolides from cyclopropenyl carboxylic acid and electrondeficient olefins or isatins.The reaction proceeds via carboxylic acid insertion of carbenoid initiated by an achiral rhodium salt,followed by chiral Lewis acid-mediated enantioselective trapping of the resulting carboxylic oxonium ylides with enones and isatins.Various enantioenrichedγ-butenolides were obtained in high yields(up to 99%)with excellent stereoselectivities(up to>19:1 dr and up to 96%ee)under mild conditions by low catalyst loading(S/C=200).The potential application of these methods was demonstrated by the gram-scale synthesis ofγ-butenolides and their further transformations into other bioactive molecules.
基金the National Natural Science Foundation of China(Nos.82003592(TS),92056201(WH)and 82201376(SC))Key-Area Research and Development Program of Guangdong Province(No.2022B1111050003)(WH)+1 种基金Shenzhen Science and Technology Innovation Project(No.20200812143116001)(SC)Basic Research Foundation of Guangdong province(No.2021A1515011129)(SC).
文摘We herein reported a sustainable synthesis of 3,3-disubstituted oxindoles via a Michael-type reaction based on the CuBr-catalysed capture of carboxylic oxonium ylides with isatylidene malononitrile.The reaction is characterized by a high atom economy and low economic constraints.The catalyst CuBr could be conveniently recyclized.The products of the reaction were found to be inhibitory against Na ion channels.We expect the reaction to shed the light on synthesis of biologically interesting molecules directed by principles of green chemistry.
基金supported by the National Natural Science Foundation of China(22001268,21973113,81973176)the Guangdong Provincial Key Laboratory of Chiral Molecule and Drug Discovery(2019B030301005)+2 种基金the Program for Guangdong Introducing Innovative and Entrepreneurial Teams(2016ZT06Y337)the Guangdong Natural Science Fund(2020A1515010614)Key-Area Research and Development Program of Guangdong Province(2022B1111050003)。
文摘A chiral dirhodium complex is an effective and robust catalyst for asymmetric carbene transformations.However,dirhodiumcatalyzed asymmetric ylide interception processes are rare,mainly because of the dissociation of the metal catalyst before the stereo-determining step.Herein,we report a chiral dirhodium(Ⅱ)-catalyzed asymmetric annulation of vinyl diazoesters withα-hydroxyl ketones,which provides an efficient way to form chiral 2,3-dihydropyrans in good yields with excellent diastereoselectivities and enantioselectivities.This article is the first example of the chiral dirhodium complex–controlled asymmetric aldol-type interception of an in situ–formed oxonium ylide.The origin of the high stereoselectivity is well expounded via experimental and computational studies.These generated chiral products exhibit potent antiproliferation activity in three tested cancer cell lines,namely HCT116(colon cancer),A549(lung adenocarcinoma),and SJSA-1(osteosarcoma cancer).
基金supported by the National Key Basic Research Program of China(973 program,2013CB934101)National Natural Science Foundation of China(21433002,21573046)+1 种基金China Postdoctoral Science Foundation(2016M601492)International Science and Technology Cooperation Projects of Guangxi(15104001-5)~~
文摘Production o f aromatics from lignin has attracted much attention. Because of the coexistence of C-O and C-C bonds and their complex combinations in the lignin macromolecular network, a plausible roadmap for developing a lignin catalytic decomposition process could be developed by exploring the transformation mechanisms of various model compounds. Herein, decomposition of a lignin model compound, 2-phenoxyacetophenone （2-PAP）, was investigated over several ce-sium-exchanged polyoxometalate （Cs-POM） catalysts. Decomposition of 2-PAP can follow two dif-ferent mechanisms： an active hydrogen transfer mechanism or an oxonium cation mechanism. The mechanism for most reactions depends on the competition between the acidity and redox proper-ties of the catalysts. The catalysts of POMs perform the following functions： promoting active hy-drogen liberated from ethanol and causing formation of and then temporarily stabilizing oxonium cations from 2-PAP. The use of Cs-PMo, which with strong redox ability, enhances hydrogen libera-tion and promotes liberated hydrogen transfer to the reaction intermediates. As a consequence, complete conversion of 2-PAP （〉99%） with excellent selectivities to the desired products （98.6% for phenol and 91.1% for acetophenone） can be achieved.
基金Supported by the National Natural Science Foundation of China
文摘The homogeneous system of 12-tungstophosphoric acid and diethylene glycol was studied using IR and NMR spectra. It was found that the protons in 12-tungstophosphoric acid formed proton oxonium ions with the hydroxyl oxygen in diethylene glycol by hydrogen-bonds, and the formed proton oxonium ions could react with the terminal oxygens of heteropoly anions. The dehydration-cyclization mechanism of diethylene glycol in the presence of heteropoly acid was also proposed.
文摘The mechanisms of insertion of O-H bond of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2 C12. The formation of free alcoholic oxonium ylides is found to be impossible. Alcoholic oxonium ylide are formed as the intermediates before beth the stepwise and the concerted transition states of insertion of O-H bend of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol. With re- gard to the mechanisms of insertion of O-H of Rh（ Ⅱ ） -methylene carbene into alcohols, analysis of the energy bartiers of the two mechanisms indicate that the stepwise mechanism is more plausible than the concerted mechanism.
