The catalytic asymmetric dipolar cycloaddition reaction is efficient for the construction of various chiral valuable carbo-and heterocycles.Thus,the design and exploration of new dipoles and the subsequent control of ...The catalytic asymmetric dipolar cycloaddition reaction is efficient for the construction of various chiral valuable carbo-and heterocycles.Thus,the design and exploration of new dipoles and the subsequent control of their reactivity for various stereoselective cycloadditions are significant aspects of modern organic synthesis.Herein,we have developed a series of vinyl cyclic carbamates containing an oxazolidine-2,4–dione fragment and used them as reactive precursors for in situ generation of amide-based aza-π-allylpalladium 1,3-dipoles,which could be applied to asymmetric decarboxylative 1,3-dipolar cycloaddition with different types of dipolarophiles containing C=C,C=N,and C=O double bonds.This strategy provides an opportunity for the synthesis of previously unusual structures,such as highly functionalized optically pure pyrrolidin-2-ones,imidazolidin-4-ones,and oxazolidin-4-ones.This protocol also has significant features including wide substrate scope,mild reaction conditions,simple operation,and good to excellent results(70 examples,up to 99%yield,>20:1 dr and 99%ee).This unique method significantly expands the reaction range of the amide-based aza-π-allylpalladium 1,3-dipoles compared to the precedents.展开更多
The deoxygenation of organic acids, important biomass feedstocks and derivatives, to synthesize hydrocarbon products under mild electrochemical conditions, holds significant importance for the production of carbon-neu...The deoxygenation of organic acids, important biomass feedstocks and derivatives, to synthesize hydrocarbon products under mild electrochemical conditions, holds significant importance for the production of carbon-neutral biofuels. There is still limited research on the influential factors of the electrochemical decarboxylation reaction of medium-chain fatty acids. In this study, n-octanoic acid (OA) was chosen as the research subject to investigate the electrochemical decarboxylation behavior of OA on a platinum electrode, focusing on the influence of different alkali metal cations (Li^(+), Na^(+), K^(+)), common anions (SO^(4)^(2−), Cl^(−)), and electrolyte pH. It was found that KOH as an electrolyte exhibited the best performance for OA. Possibly, the larger size of K^(+) increased the alkalinity of the electrode surface, facilitating OA deprotonation. LiOH electrolyte reduced the solubility of OA, thereby inhibiting the decarboxylation reaction. SO^(4)^(2−) exhibited a weak promoting effect on the decarboxylation reaction of OA, while Cl^(−) showed no adverse effect although Cl^(−) may adsorb on the electrode surface. Furthermore, unlike short-chain fatty acids, medium-chain OA can only achieve efficient decarboxylation under alkaline conditions due to its solubility properties. This study provides references and foundations for future efforts to enhance the efficiency of electrochemical decarboxylation synthesis of hydrocarbon biofuels from medium-chain fatty acids.展开更多
The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal...The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali,we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance.The results showed that the ionic liquid[Bmim]BF_(4) can affect the crystal growth of hydroxyapatite,provide fluoride ion for fluorination of hydroxyapatite,and adjust the surface acidity and basicity,morphology,textural properties,crystallinity,and composition of hydroxyapatite.The[Bmim]BF4 dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system,thus changing the degree of fluoridation of hydroxyapatite.High fluoride-ion concentration can lead to the formation of CaF_(2) and thus significantly decrease the catalytic performance of hydroxyapatite.The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis,leading to different catalytic performance.The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows:a mass ratio of[Bmim]BF4 to calcium salt=0.2:1,a hydrothermal time of 12 h,and a hydrothermal temperature of 130℃.A maximal methacrylic acid yield of 54.7%was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions(250℃ and 2 MPa of N_(2))in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.展开更多
Regulation of cell fate requires the establishment and erasure of 5-methylcytosine(5mC) in genomic DNA.The formation of 5mC is achieved by DNA cytosine methyltransferases(DNMTs),whereas the removal of5mC can be accomp...Regulation of cell fate requires the establishment and erasure of 5-methylcytosine(5mC) in genomic DNA.The formation of 5mC is achieved by DNA cytosine methyltransferases(DNMTs),whereas the removal of5mC can be accomplished by various pathways.Aside from ten-eleven translocation(TET)-mediated oxidation of 5mC followed by thymine DNA glycosylase(TDG)-initiated base excision repair(BER),the direct deformylation of 5-formylcytosine(5fC) and decarboxylation of 5-carboxylcytosine(5caC) have also been discovered as the novel DNA demethylation pathways.Although these novel demethylation pathways have been identified in stem cells and somatic cells,their precise roles in regulating cell fate remain unclear.Here,we differentiate mouse embryonic stem cells(mESCs) into mouse embryoid bodies(mEBs),followed by further differentiation into mouse neural stem cells(mNSCs) and finally into mouse neurons(mNeurons).During this sequential differentiation process,we employ probe molecules,namely2'-fluorinated 5-formylcytidine(F-5fC) and 2'-fluorinated 5-carboxyldeoxycytidine(F-5caC),for metabolic labeling.The results of mass spectrometry(MS) analysis demonstrate the deformylation and decarboxylation activities are progressively decreased and increased respectively during differentiation process,and this opposite demethylation tendency is not associated with DNMTs and TETs.展开更多
The carboxyl terminal of sodium oleate has a stronger polarity than that of oleic acid;this terminal is more likely to be dipole polarized and ionically conductive in a microwave field.Sodium oleate was used as the mo...The carboxyl terminal of sodium oleate has a stronger polarity than that of oleic acid;this terminal is more likely to be dipole polarized and ionically conductive in a microwave field.Sodium oleate was used as the model compound to study the decarboxylation of oleic acid leading to hydrocarbon formation via microwave-assisted pyrolysis technology.The pyrolysis gas,liquid,and solid products were precisely analyzed to deduce the mechanism for decarboxylation of sodium oleate.Microwave energy was able to selectively heat the carboxyl terminal of sodium oleate.During decarboxylation,the double bond in the long hydrocarbon chain formed a p-πconjugated system with the carbanion intermediate.The resulting p-πconjugated system was more stable and beneficial to the pyrolysis reaction(decarboxylation,terminal allylation,isomerization,and aromatization).The physical properties of pyrolysis liquid were generally similar to those of diesel fuel,thereby demonstrating the possible use of microwaves for controlling the decarboxylation of sodium oleate in order to manufacture renewable hydrocarbon fuels.展开更多
Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid...Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.展开更多
Two three-dimensional lanthanide（Ⅲ） coordination polymers with the formula [Ln（PYDC）（NA）（H2O）]n [Ln=Gd（1）, Eu（2）, H2PYDC=pyridine-2,5-bicarboxylic acid, HNA=nicotinic acid] have been hydrothermally synthe...Two three-dimensional lanthanide（Ⅲ） coordination polymers with the formula [Ln（PYDC）（NA）（H2O）]n [Ln=Gd（1）, Eu（2）, H2PYDC=pyridine-2,5-bicarboxylic acid, HNA=nicotinic acid] have been hydrothermally synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. The NA came from in situ decarboxylation of the part of PYDC. X-ray single crystal structural analyses reveal that complexes 1 and 2 are isomorphous, they possess the 43.63 topology assembled by Gd^3＋/Eu^3＋ and two different multidentate carboxylate ligands Magnetic measurements show that antiferromagnetic coupling exists between adjacent Gd^3＋ ions in complex 1. The complex 2 exhibits the corresponding characteristic luminescence in the visible region under an excitation at 305 nm.展开更多
An assembly of Keggin polyoxomolybdate and organic substrate （Hbipy）3[PM01204o] （1, bipy = 2,2＇- bipyridine） was synthesized and characterized by elemental analysis, infrared spectrum, and single- crystal X-ray a...An assembly of Keggin polyoxomolybdate and organic substrate （Hbipy）3[PM01204o] （1, bipy = 2,2＇- bipyridine） was synthesized and characterized by elemental analysis, infrared spectrum, and single- crystal X-ray analysis. The ligand bipy of compound 1 was generated by a decarboxylation coupling reaction of H2pdc （H2pdc = pyridine-2,6-dicarboxylic acid） in situ under hydrothermal reaction conditions and the control experiments illustrate that La（NO3）3 or Ce（NO3）3, which does not appear in the final structure, is necessary for the decarboxylation coupling reaction. Moreover, compound 1 displays strong photoluminescence property in the solid state at room temperature.展开更多
A metal-free photocatalytic oxidative decarboxylation reaction at room temperature was developed for the synthesis of aromatic aldehydes and ketones from the corresponding arylacetic acids.The reaction was realized un...A metal-free photocatalytic oxidative decarboxylation reaction at room temperature was developed for the synthesis of aromatic aldehydes and ketones from the corresponding arylacetic acids.The reaction was realized under blue-light irradiation by adding 1 mol%of 4 CzIPN as photocatalyst and air as oxidant.This reaction represents a novel decarboxylation of a sp^3-hybridized carboxylic acids without traditional heating,additional oxidants,and metal reagents under mild conditions.展开更多
Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, ...Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.展开更多
Pyridinium ylids 4 were generated as reaction intermediates from the decarboxylation of pyridinium betaines 3, which were prepared from the reactions of a-amino acid ester hydrochlorides with 2, 4, 6-triphenylpyrylium...Pyridinium ylids 4 were generated as reaction intermediates from the decarboxylation of pyridinium betaines 3, which were prepared from the reactions of a-amino acid ester hydrochlorides with 2, 4, 6-triphenylpyrylium tetrafluoroborate. Protonation, addition and substitution reactions of 4 with electrophiles were studied in this paper.展开更多
The reaction between Ce (IV ) and NTA was investigated titrimetrically and spectrophotometrically. Two equivalents of Ce( IV ) are reduced per mole of NTA almost instantaneously at room temperature. With increasing re...The reaction between Ce (IV ) and NTA was investigated titrimetrically and spectrophotometrically. Two equivalents of Ce( IV ) are reduced per mole of NTA almost instantaneously at room temperature. With increasing reaction time an ultimate of about 7 equivalents of Ce( IV) is consumed per mole of NTA at room temperature. Carbon dioxide, formaldehyde and dimethylamine are the major and readily detectable products of oxidation of NTA by Ce( IV ). The rates of the reaction in HClO4 were measured spectrophotometricaUy using the stopped flow technique. The effects of both acidity of the medium and added salts support and extend preliminary results.展开更多
The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calcula...The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calculation, CPCM full optimization is better to model solvent environments to gain reasonable reaction mechanisms. The π interactions play a significant role in the decarboxylation of pyrrole-2-carboxylic acid （R）. Firstly, the a hydrogen is protonated, but all of the carbonyl hydration pathways bear relatively higher energy barriers. The carbonyl group can rove over the pyrrole ring, but it does not lead to the speciation of pyrrole and protonated carbon dioxide for the latter is an energy-rich species. The decarboxylation mechanism proposed here is that, the protonated pyrrole-2-carboxylic acid （RH） decarboxylates via direct C-C bond cleavage with the aid of a water molecule to accommodate the proton on the carbonyl group.展开更多
In this paper, the charge distribution, the chemical bond order and the reactive performance of carboxylic acid model compounds on acidic catalyst were investigated by using molecular simulation technology. The simula...In this paper, the charge distribution, the chemical bond order and the reactive performance of carboxylic acid model compounds on acidic catalyst were investigated by using molecular simulation technology. The simulation results showed that the bond order of C—O was higher than that of C—C, and C—C bond connected to the carbon atom in the carboxyl radical had the lowest bond order. The charge distributions of model naphthenic acids were similar in characteristics that the negative charges were concentrated on carboxyls. According to the simulation results, the mechanisms of catalytic decar- boxylation over acidic solid catalyst were proposed, and a new route was put forward regarding removal of the naphthenic acid from crude oil through catalytic decarboxylation.展开更多
The energy barriers of thermal decarboxylation reactions of petroleum acids and catalytic decarboxylation reactions of Bronsted acid and Lewis acid were analyzed using molecular simulation technology. Compared with th...The energy barriers of thermal decarboxylation reactions of petroleum acids and catalytic decarboxylation reactions of Bronsted acid and Lewis acid were analyzed using molecular simulation technology. Compared with thermal decarboxylation reactions of petroleum acids, the decarboxylation reactions by acid catalysts were easier to occur. The decarboxylaton effect by Lewis acid was better than Bronsted acid. The mechanisms of catalytic decarboxylation over acid catalyst were also verified by experiments on a fixed bed and a fluidized bed, the experimental results showed that the rate of acid removal could reach up to 97% over the acidic catalyst at a temperature above 400℃.展开更多
A new luminescent dinuclear cluster complex [Cd2（pzc）2（AmTAZ）（HEO）4（NO3）]·NO3 （Hpzc = pyrazine-2-carboxylic acid, AmTAZ = 3-amino-4H-1,2,4-triazole） has been prepared by the assembly of Cdn with pyrazin...A new luminescent dinuclear cluster complex [Cd2（pzc）2（AmTAZ）（HEO）4（NO3）]·NO3 （Hpzc = pyrazine-2-carboxylic acid, AmTAZ = 3-amino-4H-1,2,4-triazole） has been prepared by the assembly of Cdn with pyrazine-2,3-dicarboxylic acid and 3-amino-lH-1,2,4-triazole-5-car- boxylic acid ligands under hydrothermal conditions, in which in situ decarboxylation of H2pzdc and HAmTZC ligands simultaneously occurred, and HEpzdc was transformed into Hpzc while HAmTZC into AmTAZ. The crystal structure is of triclinic, space group P1 with a = 7.096（2）, b = 11.140（4）, c = 14.887（5）А, α= 92.641（4）, β= 91.348（6）, γ= 96.058（6）°, V = 1168.5（7）А^3, C12H18Cd2N10O14, Mr = 751.16, Z = 2, Dc = 2.126 g/cm^3, F（000） = 730,μ=1.910 mm^-1, R = 0.0320 and wR = 0.0998 for 4549 observed reflections （I 〉 2σ（I））. The dinuclear cluster of 1 is extended into a 3D supramolecular architecture through intermolecular hydrogen bonding interactions. Complex I exhibits strong blue photoluminescence at room temperature.展开更多
It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pu...It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 - 10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.展开更多
The mechanism and the final outcome of the Knoevenagel-Doebner reaction are discussed. The condensation reaction between different hydroxy-substituted aromatic aldehydes and malonic acid is performed using piperidine ...The mechanism and the final outcome of the Knoevenagel-Doebner reaction are discussed. The condensation reaction between different hydroxy-substituted aromatic aldehydes and malonic acid is performed using piperidine as organocatalyst. The key role of the catalyst is clearly pointed out during the decarboxylation of ferulic acid, without the use of a strong decarboxylating agent, leading to a 4-vinylphenol derivative. Based on the results obtained, the studied pathway may be important in the understanding of vinylphenol production during malting and brewing of wheat and barley grains. Finally, changing the solvent of the reaction from pyridine to water in the Knoevenagel-Doebner reaction of 4-hydroxybenzaldehydes, dimerization of resulting styrene derivatives is observed. These results can be of interest also in the field of food chemistry, since cinnamic acids are frequently found in fruits and vegetables used for human consumption.展开更多
A tandem Diels–Alder reaction/Claisen rearrangement/decarboxylation strategy of N-allenamides (or aryloxyallenes) with 3-alkoxycarbonyl-2-pyrones has been developed for the efficient synthesis of diarylmethanes with ...A tandem Diels–Alder reaction/Claisen rearrangement/decarboxylation strategy of N-allenamides (or aryloxyallenes) with 3-alkoxycarbonyl-2-pyrones has been developed for the efficient synthesis of diarylmethanes with moderate to good yields. The reaction exhibits good functional group tolerance and can be applied to late-stage modifications of known drug molecules. Mechanistic studies indicate that the ester group at the 3-position of 2-pyrones is essential, and the initial Diels–Alder reaction between the 2-pyrones and the proximal C=C bond of the N-allenamides (or aryloxyallenes) is crucial for the success of the reaction.展开更多
Post-polymerization modification provides an important approach to tuning the material properties of obtained polymers.In this work,we demonstrated a rational design of novel vinylcyclopropane monomer bearing a pendan...Post-polymerization modification provides an important approach to tuning the material properties of obtained polymers.In this work,we demonstrated a rational design of novel vinylcyclopropane monomer bearing a pendant N-hydroxylphthalimide redox ester,and explored its radical ring-opening polymerization behavior under visible-light conditions.Photochemical decarboxylation of resulted polymer provided unique access to poly(vinylcyclopropane)bearing single ester group in each repeating unit.This decarboxylative modification has greatly reshaped the thermal and mechanical properties,converting a glassy polymer into a soft,ductile,and rubber-like material.展开更多
基金the National Natural Science Foundation of China(Nos.22271027,22171029,21901024,21871252,21801024,and 21801026)the Sichuan Science and Technology Program(No.2021YFS0315)the Talent Program of Chengdu University(Nos.2081919035 and 2081921038)。
文摘The catalytic asymmetric dipolar cycloaddition reaction is efficient for the construction of various chiral valuable carbo-and heterocycles.Thus,the design and exploration of new dipoles and the subsequent control of their reactivity for various stereoselective cycloadditions are significant aspects of modern organic synthesis.Herein,we have developed a series of vinyl cyclic carbamates containing an oxazolidine-2,4–dione fragment and used them as reactive precursors for in situ generation of amide-based aza-π-allylpalladium 1,3-dipoles,which could be applied to asymmetric decarboxylative 1,3-dipolar cycloaddition with different types of dipolarophiles containing C=C,C=N,and C=O double bonds.This strategy provides an opportunity for the synthesis of previously unusual structures,such as highly functionalized optically pure pyrrolidin-2-ones,imidazolidin-4-ones,and oxazolidin-4-ones.This protocol also has significant features including wide substrate scope,mild reaction conditions,simple operation,and good to excellent results(70 examples,up to 99%yield,>20:1 dr and 99%ee).This unique method significantly expands the reaction range of the amide-based aza-π-allylpalladium 1,3-dipoles compared to the precedents.
基金The authors gratefully acknowledge the financial support from Shanghai Pujiang Program(20PJ1404800)“Scientific and Technical Innovation Action Plan”Basic Research Field of Shanghai Science and Technology Committee(19JC1410500).
文摘The deoxygenation of organic acids, important biomass feedstocks and derivatives, to synthesize hydrocarbon products under mild electrochemical conditions, holds significant importance for the production of carbon-neutral biofuels. There is still limited research on the influential factors of the electrochemical decarboxylation reaction of medium-chain fatty acids. In this study, n-octanoic acid (OA) was chosen as the research subject to investigate the electrochemical decarboxylation behavior of OA on a platinum electrode, focusing on the influence of different alkali metal cations (Li^(+), Na^(+), K^(+)), common anions (SO^(4)^(2−), Cl^(−)), and electrolyte pH. It was found that KOH as an electrolyte exhibited the best performance for OA. Possibly, the larger size of K^(+) increased the alkalinity of the electrode surface, facilitating OA deprotonation. LiOH electrolyte reduced the solubility of OA, thereby inhibiting the decarboxylation reaction. SO^(4)^(2−) exhibited a weak promoting effect on the decarboxylation reaction of OA, while Cl^(−) showed no adverse effect although Cl^(−) may adsorb on the electrode surface. Furthermore, unlike short-chain fatty acids, medium-chain OA can only achieve efficient decarboxylation under alkaline conditions due to its solubility properties. This study provides references and foundations for future efforts to enhance the efficiency of electrochemical decarboxylation synthesis of hydrocarbon biofuels from medium-chain fatty acids.
基金supported by National Natural Science Foundation of China(21978066)Basic Research Program of Hebei Province for Natural Science Foundation and Key Basic Research Project(18964308D)the Key Program of Natural Science Foundation of Hebei Province(B2020202048).
文摘The synthesis of methacrylic acid from biomass-derived itaconic acid is a green route,for it can get rid of the dependence on fossil resource.In order to solve the problems on this route such as use of a preciousmetal catalyst and a corrosive homogeneous alkali,we prepared a series of hydroxyapatite catalysts by an ionic liquid-assisted hydrothermal method and evaluated their catalytic performance.The results showed that the ionic liquid[Bmim]BF_(4) can affect the crystal growth of hydroxyapatite,provide fluoride ion for fluorination of hydroxyapatite,and adjust the surface acidity and basicity,morphology,textural properties,crystallinity,and composition of hydroxyapatite.The[Bmim]BF4 dosage and hydrothermal temperature can affect the fluoride ion concentration in the hydrothermal system,thus changing the degree of fluoridation of hydroxyapatite.High fluoride-ion concentration can lead to the formation of CaF_(2) and thus significantly decrease the catalytic performance of hydroxyapatite.The hydrothermal time mainly affects the growth of hydroxyapatite crystals on the c axis,leading to different catalytic performance.The suitable conditions for the preparation of this fluoridized hydroxyapatite are as follows:a mass ratio of[Bmim]BF4 to calcium salt=0.2:1,a hydrothermal time of 12 h,and a hydrothermal temperature of 130℃.A maximal methacrylic acid yield of 54.7%was obtained using the fluoridized hydroxyapatite under relatively mild reaction conditions(250℃ and 2 MPa of N_(2))in the absence of a precious-metal catalyst and a corrosive homogeneous alkali.
基金supported by the National Key R&D Program of China (Nos.2022YFC3400700,2022YFA0806600)the National Natural Science Foundation of China (No.22074110)+3 种基金Guangdong Basic and Applied Basic Research Foundation (No.2022A1515110550)Central Public-interest Scientific Institution Basal Research Fund,South China Sea Fisheries Research Institute,CAFS (No.2021TS02)Guangzhou Basic and Applied Basic Research Foundation (No.2023A04J1337)Central Public-interest Scientific Institution Basal Research Fund,CAFS (No.2023TD78)。
文摘Regulation of cell fate requires the establishment and erasure of 5-methylcytosine(5mC) in genomic DNA.The formation of 5mC is achieved by DNA cytosine methyltransferases(DNMTs),whereas the removal of5mC can be accomplished by various pathways.Aside from ten-eleven translocation(TET)-mediated oxidation of 5mC followed by thymine DNA glycosylase(TDG)-initiated base excision repair(BER),the direct deformylation of 5-formylcytosine(5fC) and decarboxylation of 5-carboxylcytosine(5caC) have also been discovered as the novel DNA demethylation pathways.Although these novel demethylation pathways have been identified in stem cells and somatic cells,their precise roles in regulating cell fate remain unclear.Here,we differentiate mouse embryonic stem cells(mESCs) into mouse embryoid bodies(mEBs),followed by further differentiation into mouse neural stem cells(mNSCs) and finally into mouse neurons(mNeurons).During this sequential differentiation process,we employ probe molecules,namely2'-fluorinated 5-formylcytidine(F-5fC) and 2'-fluorinated 5-carboxyldeoxycytidine(F-5caC),for metabolic labeling.The results of mass spectrometry(MS) analysis demonstrate the deformylation and decarboxylation activities are progressively decreased and increased respectively during differentiation process,and this opposite demethylation tendency is not associated with DNMTs and TETs.
基金the National Natural Science Foundation of China(No.21266022)the National High Technology Research and Development Program 863(2012AA101800-03+4 种基金2012AA02120562012AA021704)the International Cooperation of Jiangxi Province(No.20101208)the International Science & Technology Cooperation Program of China(No.2010DFB63750)the Natural Science Foundation of Jiangxi Province(No.2008GZH0047)
文摘The carboxyl terminal of sodium oleate has a stronger polarity than that of oleic acid;this terminal is more likely to be dipole polarized and ionically conductive in a microwave field.Sodium oleate was used as the model compound to study the decarboxylation of oleic acid leading to hydrocarbon formation via microwave-assisted pyrolysis technology.The pyrolysis gas,liquid,and solid products were precisely analyzed to deduce the mechanism for decarboxylation of sodium oleate.Microwave energy was able to selectively heat the carboxyl terminal of sodium oleate.During decarboxylation,the double bond in the long hydrocarbon chain formed a p-πconjugated system with the carbanion intermediate.The resulting p-πconjugated system was more stable and beneficial to the pyrolysis reaction(decarboxylation,terminal allylation,isomerization,and aromatization).The physical properties of pyrolysis liquid were generally similar to those of diesel fuel,thereby demonstrating the possible use of microwaves for controlling the decarboxylation of sodium oleate in order to manufacture renewable hydrocarbon fuels.
基金supported by the National Natural Science Foundation of China(Grant No.21978066)Basic Research Program of Hebei Province for Natural Science Foundation and Key Basic Research Project(Grant No.18964308D)the Key Program of Natural Science Foundation of Hebei Province(Grant No.B2020202048).
文摘Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.
基金Supported by the Education Department Science Foundation of Liaoning Province(No.2008581)the Doctor Foundation of Liaoning Province(No.20071016)+1 种基金SRF for ROCS,SEM(No.200908)Liaoning BaiQian Wan Talents Program
文摘Two three-dimensional lanthanide（Ⅲ） coordination polymers with the formula [Ln（PYDC）（NA）（H2O）]n [Ln=Gd（1）, Eu（2）, H2PYDC=pyridine-2,5-bicarboxylic acid, HNA=nicotinic acid] have been hydrothermally synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction. The NA came from in situ decarboxylation of the part of PYDC. X-ray single crystal structural analyses reveal that complexes 1 and 2 are isomorphous, they possess the 43.63 topology assembled by Gd^3＋/Eu^3＋ and two different multidentate carboxylate ligands Magnetic measurements show that antiferromagnetic coupling exists between adjacent Gd^3＋ ions in complex 1. The complex 2 exhibits the corresponding characteristic luminescence in the visible region under an excitation at 305 nm.
基金supported by the National Natural Science Foundation of China(Nos.21173021,21231002, 21276026,20801036,51002180)the 111 Project(No. B07012)the Program of Cooperation of the Beijing Education Commission(No.20091739006)
文摘An assembly of Keggin polyoxomolybdate and organic substrate （Hbipy）3[PM01204o] （1, bipy = 2,2＇- bipyridine） was synthesized and characterized by elemental analysis, infrared spectrum, and single- crystal X-ray analysis. The ligand bipy of compound 1 was generated by a decarboxylation coupling reaction of H2pdc （H2pdc = pyridine-2,6-dicarboxylic acid） in situ under hydrothermal reaction conditions and the control experiments illustrate that La（NO3）3 or Ce（NO3）3, which does not appear in the final structure, is necessary for the decarboxylation coupling reaction. Moreover, compound 1 displays strong photoluminescence property in the solid state at room temperature.
基金the National Natural Science Foundation of China(Nos.21501010,21971224)Innovation and Entrepreneurship Training Program of Zhengzhou University(No.2019cxcy509)Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation(No.2019CL03)。
文摘A metal-free photocatalytic oxidative decarboxylation reaction at room temperature was developed for the synthesis of aromatic aldehydes and ketones from the corresponding arylacetic acids.The reaction was realized under blue-light irradiation by adding 1 mol%of 4 CzIPN as photocatalyst and air as oxidant.This reaction represents a novel decarboxylation of a sp^3-hybridized carboxylic acids without traditional heating,additional oxidants,and metal reagents under mild conditions.
文摘Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.
基金We want to express our sincere appreciation to Professor Joe Wilson of University of Kentucky and Professor Xiulin Ye of Peking University for their favorable suggestions and assistance for the work.
文摘Pyridinium ylids 4 were generated as reaction intermediates from the decarboxylation of pyridinium betaines 3, which were prepared from the reactions of a-amino acid ester hydrochlorides with 2, 4, 6-triphenylpyrylium tetrafluoroborate. Protonation, addition and substitution reactions of 4 with electrophiles were studied in this paper.
文摘The reaction between Ce (IV ) and NTA was investigated titrimetrically and spectrophotometrically. Two equivalents of Ce( IV ) are reduced per mole of NTA almost instantaneously at room temperature. With increasing reaction time an ultimate of about 7 equivalents of Ce( IV) is consumed per mole of NTA at room temperature. Carbon dioxide, formaldehyde and dimethylamine are the major and readily detectable products of oxidation of NTA by Ce( IV ). The rates of the reaction in HClO4 were measured spectrophotometricaUy using the stopped flow technique. The effects of both acidity of the medium and added salts support and extend preliminary results.
基金supported by the National Natural Science Foundation of China(11174215)Natural Science Foundation of Shandong Province(ZR2012BL10 and ZR2010BL017)+1 种基金the University Science and Technology Project of Shandong Province(No.J13LD05)the Science and Technology Planning Project of Tai'an City(20102024)
文摘The decarboxylation of pyrrole-2-carboxylic acid in acid solutions was elucidated by full optimization with the CPCM solvation model at the B3LYP/6-31 l＋＋G（d,p） level. Compared with the single-point energy calculation, CPCM full optimization is better to model solvent environments to gain reasonable reaction mechanisms. The π interactions play a significant role in the decarboxylation of pyrrole-2-carboxylic acid （R）. Firstly, the a hydrogen is protonated, but all of the carbonyl hydration pathways bear relatively higher energy barriers. The carbonyl group can rove over the pyrrole ring, but it does not lead to the speciation of pyrrole and protonated carbon dioxide for the latter is an energy-rich species. The decarboxylation mechanism proposed here is that, the protonated pyrrole-2-carboxylic acid （RH） decarboxylates via direct C-C bond cleavage with the aid of a water molecule to accommodate the proton on the carbonyl group.
文摘In this paper, the charge distribution, the chemical bond order and the reactive performance of carboxylic acid model compounds on acidic catalyst were investigated by using molecular simulation technology. The simulation results showed that the bond order of C—O was higher than that of C—C, and C—C bond connected to the carbon atom in the carboxyl radical had the lowest bond order. The charge distributions of model naphthenic acids were similar in characteristics that the negative charges were concentrated on carboxyls. According to the simulation results, the mechanisms of catalytic decar- boxylation over acidic solid catalyst were proposed, and a new route was put forward regarding removal of the naphthenic acid from crude oil through catalytic decarboxylation.
基金the National Key Basic Re-search and Development Program (No. 2006CB202505).
文摘The energy barriers of thermal decarboxylation reactions of petroleum acids and catalytic decarboxylation reactions of Bronsted acid and Lewis acid were analyzed using molecular simulation technology. Compared with thermal decarboxylation reactions of petroleum acids, the decarboxylation reactions by acid catalysts were easier to occur. The decarboxylaton effect by Lewis acid was better than Bronsted acid. The mechanisms of catalytic decarboxylation over acid catalyst were also verified by experiments on a fixed bed and a fluidized bed, the experimental results showed that the rate of acid removal could reach up to 97% over the acidic catalyst at a temperature above 400℃.
基金supported by the State Key Basic Research and Development Plan of China (2007CB815302)the Chinese Academy of sciences (KJCX2-YW-M05)+2 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences, the NSF (E0620005) of Fujian Provincethe Major Special Foundation of Fujian Province (2005HZ1027), (2005HZ01-1)the Fund of Fujian Key Laboratory of Nanomaterials (2006L2005)
文摘A new luminescent dinuclear cluster complex [Cd2（pzc）2（AmTAZ）（HEO）4（NO3）]·NO3 （Hpzc = pyrazine-2-carboxylic acid, AmTAZ = 3-amino-4H-1,2,4-triazole） has been prepared by the assembly of Cdn with pyrazine-2,3-dicarboxylic acid and 3-amino-lH-1,2,4-triazole-5-car- boxylic acid ligands under hydrothermal conditions, in which in situ decarboxylation of H2pzdc and HAmTZC ligands simultaneously occurred, and HEpzdc was transformed into Hpzc while HAmTZC into AmTAZ. The crystal structure is of triclinic, space group P1 with a = 7.096（2）, b = 11.140（4）, c = 14.887（5）А, α= 92.641（4）, β= 91.348（6）, γ= 96.058（6）°, V = 1168.5（7）А^3, C12H18Cd2N10O14, Mr = 751.16, Z = 2, Dc = 2.126 g/cm^3, F（000） = 730,μ=1.910 mm^-1, R = 0.0320 and wR = 0.0998 for 4549 observed reflections （I 〉 2σ（I））. The dinuclear cluster of 1 is extended into a 3D supramolecular architecture through intermolecular hydrogen bonding interactions. Complex I exhibits strong blue photoluminescence at room temperature.
文摘It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 - 10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.
文摘The mechanism and the final outcome of the Knoevenagel-Doebner reaction are discussed. The condensation reaction between different hydroxy-substituted aromatic aldehydes and malonic acid is performed using piperidine as organocatalyst. The key role of the catalyst is clearly pointed out during the decarboxylation of ferulic acid, without the use of a strong decarboxylating agent, leading to a 4-vinylphenol derivative. Based on the results obtained, the studied pathway may be important in the understanding of vinylphenol production during malting and brewing of wheat and barley grains. Finally, changing the solvent of the reaction from pyridine to water in the Knoevenagel-Doebner reaction of 4-hydroxybenzaldehydes, dimerization of resulting styrene derivatives is observed. These results can be of interest also in the field of food chemistry, since cinnamic acids are frequently found in fruits and vegetables used for human consumption.
基金supported by the NSFC(22071210,22101033,22201023,22271242)the Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology(BM2012110)+1 种基金the Natural Science Foundation of Jiangsu Province(BK20210849)the Innovation&Entrepreneurship Talents Plan of Jiangsu Province(JSSCRC2021536).
文摘A tandem Diels–Alder reaction/Claisen rearrangement/decarboxylation strategy of N-allenamides (or aryloxyallenes) with 3-alkoxycarbonyl-2-pyrones has been developed for the efficient synthesis of diarylmethanes with moderate to good yields. The reaction exhibits good functional group tolerance and can be applied to late-stage modifications of known drug molecules. Mechanistic studies indicate that the ester group at the 3-position of 2-pyrones is essential, and the initial Diels–Alder reaction between the 2-pyrones and the proximal C=C bond of the N-allenamides (or aryloxyallenes) is crucial for the success of the reaction.
基金supported by the National Natural Science Foundation of China(No.22101273)the Fundamental Research Fund for the Central Universities(WK9990000111)。
文摘Post-polymerization modification provides an important approach to tuning the material properties of obtained polymers.In this work,we demonstrated a rational design of novel vinylcyclopropane monomer bearing a pendant N-hydroxylphthalimide redox ester,and explored its radical ring-opening polymerization behavior under visible-light conditions.Photochemical decarboxylation of resulted polymer provided unique access to poly(vinylcyclopropane)bearing single ester group in each repeating unit.This decarboxylative modification has greatly reshaped the thermal and mechanical properties,converting a glassy polymer into a soft,ductile,and rubber-like material.
