Mechanistic understanding of the active intermediates of 2,6-diaminopyridine(DAP) dinitration in the concentrated nitric-sulfuric acid system is of crucial importance for the selectivity control of target product, i.e...Mechanistic understanding of the active intermediates of 2,6-diaminopyridine(DAP) dinitration in the concentrated nitric-sulfuric acid system is of crucial importance for the selectivity control of target product, i.e., 2,6-diamino-3,5-dinitropyridine(DADNP). The active intermediates determining the product selectivity are theoretically studied. The HSO_(4)^(-)-NO_(2)^(+) complex is proposed as the dominant active nitrating intermediate for the first time, which shows low energy barrier(i.e., 10.19 kcal·mol^(-1),1 kcal = 4.186 k J) for direct dinitration of DAP to DADNP. The formed water during the reaction results in not only the formation of less active SO_(4)^(2-)-NO_(2)^(+) complex, but also the occurance of DAP sulfonation(DAP-SO_(3)H intermediate)to facilitate the formation of mononitration byproduct. Meanwhile, the accompanied thermal effects cause the generation of undesirable pyridine-NHNO_(2) intermediate, which is difficult to be rearranged to yield DADNP, inhibiting the reaction and thus giving low DAP conversion. The insights reported here elucidates the importance of thermal effects elimination and water content control, confirmed experimentally in the batch-and micro-reaction systems.展开更多
Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium ...Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium geometries including comparing to the AE-active ester. It was found that the Ethyl-aminothiazoly Loximate (AT) molecule fragment is almost planar sheet, but it is almost perpendicular to the plane of phosphoryl ester. Moreover, the calculated Mulliken atomic charge distribution and frontier molecular orbital analysis of these esters showed that the amino N atom connected to the Thiazole ring of the AT had the maximum negative charge, which suggested that this area had high molecular activity. The value of ΔEL-H was energy gap between EHOMO and ELUMO and indicated that compound 6a had high reaction activity. The theory calculation results can explain the reaction mechanism well and predict that the novel active phosphonate ester has a hopeful application prospect in preparation of Cephalosporin antibiotics’ intermediate.展开更多
Excessive nitrate in groundwater has emerged as a serious environmental concern. The elevated nitrate concentration in drinking water causes a serious threat to public health on account of the possible transformation ...Excessive nitrate in groundwater has emerged as a serious environmental concern. The elevated nitrate concentration in drinking water causes a serious threat to public health on account of the possible transformation of nitrate to nitrite, which is one of the main predisposing factors of methemoglobinemia [1].展开更多
Prostate cancer is the leading male cancer worldwide. There remains a controversy as to which patients have indolent disease and which patients present an aggressive disease needing treatment with intent to cure. Beca...Prostate cancer is the leading male cancer worldwide. There remains a controversy as to which patients have indolent disease and which patients present an aggressive disease needing treatment with intent to cure. Because of quality of life impairment associated with treatment by radiation or surgery, active surveillance (AS) is a valid management option to avoid or differ aggressive treatment. Traditionally, AS was reserved for men with low risk prostate cancer, however intermediate risk patients are more and more found in AS cohorts. The aim of this review is to describe the place of AS in intermediate risk patients and the perspectives offered by such a treatment modality.展开更多
The roles of intermediate conductance Ca2＋-activated K＋ channel （IKCal） in the pathogene- sis of hepatocellular carcinoma （HCC） were investigated. Immunohistochemistry and Western blotting were used to detect th...The roles of intermediate conductance Ca2＋-activated K＋ channel （IKCal） in the pathogene- sis of hepatocellular carcinoma （HCC） were investigated. Immunohistochemistry and Western blotting were used to detect the expression of IKCal protein in 50 HCC and 20 para-carcinoma tissue samples. Real-time PCR was used to detect the transcription level of IKCal mRNA in 13 HCC and 11 para-carcinoma tissue samples. The MTT assay was used to measure the function of IKCal in human HCC cell line HepG2 in vitro. TRAM-34, a specific blocker of IKCal, was used to intervene with the function of IKCal. As compared with para-carcinoma tissue, an over-expression of IKCal protein was detected in HCC tissue samples （P〈0.05）. The mRNA expression level of IKCal in HCC tissues was 2.17 times higher than that in para-carcinoma tissues. The proliferation of HepG2 cells was suppressed by TRAM-34 （0.5, 1.0, 2.0 and 4.0 pxnol/L） in vitro （P〈0.05）. Our results suggested that IKCal may play a role in the proliferation of human HCC, and IKCal blockers may represent a potential therapeutic strategy for HCC.展开更多
Palladium-catalyzed carbonylation is an efficient approach to prepare carbonyl-containing compounds with high atomic economy in synthetic organic chemistry.However,in comparison with aryl halides,carbonylation of alky...Palladium-catalyzed carbonylation is an efficient approach to prepare carbonyl-containing compounds with high atomic economy in synthetic organic chemistry.However,in comparison with aryl halides,carbonylation of alkyl halides is relatively challenging due to the decreased stability of the palladium intermediates.Carbonylation of activated alkyl halides is even more difficult,as nucleophilic substitution reactions with nucleophiles occur more easily with them.In this article,we summarize and discuss recent achievements in palladium-catalyzed carbonylative reactions of activated alkyl halides.The transformations proceed through radical intermediates which are generated in various manners.Under a relatively high pressure of carbon monoxide,the corresponding aliphatic carboxylic acid derivates were effectively prepared with various nucleophiles as the reaction partners.Besides alcohols,amines and organoboron reagents,four-component reactions in combination with alkenes or alkynes were also developed.Case-by-case reaction mechanisms are discussed as well and a personal outlook has also been provided.展开更多
The Ti/SnO2+Sb2O3/PbO2 anode with SnO2+Sb2O3 intermediate layer obtained by the polymeric precursor method (PPM) and with the conventional route was studied. The morphology and microstructure of SnO2+Sb2O3 intermediat...The Ti/SnO2+Sb2O3/PbO2 anode with SnO2+Sb2O3 intermediate layer obtained by the polymeric precursor method (PPM) and with the conventional route was studied. The morphology and microstructure of SnO2+Sb2O3 intermediate layer derived from different precursors and the top PbO2 active layer were examined by means of ESEM and XRD. The lifetime and electrocatalytic activity of the anode were also assessed by the cyclic voltammetry and accelerated lifetime test in 1.0 mol/L H2SO4 solution. It was found that precursor solvents affected lifetime, microstructure and morphology of the anode, and had little influence on electrocatalysis activity of the electrodes. The accelerated lifetime of Ti/SnO2+Sb2O3/PbO2 anode with intermediate layer prepared by PPM was 29.5 h in 1.0 mol/L H2SO4 solution, which was respectively about four times and twice that of the anode prepared with ethylene glycol and ethanol. After the anode was subjected to thermal corrosion, the lifetime still reached 27 h in contrast to the others.展开更多
Activation and surface reactions of CO and H2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions were(quasi) in situ studied using temperature programmed surface reaction spectra, diffuse reflect...Activation and surface reactions of CO and H2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions were(quasi) in situ studied using temperature programmed surface reaction spectra, diffuse reflectance Fourier transform infrared spectroscopy, inelastic neutron scattering spectroscopy and electron paramagnetic resonance. CO undergoes disproportion reaction to produce gaseous CO2 and surface carbon adatoms, and adsorbs to form surface formate species. H2 adsorption forms dominant irreversibly-adsorbed surface hydroxyl groups and interstitial H species and very minor surface Zn-H species. Surface formate species and hydroxyl groups react to produce CO2 and H2, while surface carbon adatoms are hydrogenated by surface Zn-H species sequentially to produce CH(a), CH2(a), CH3(a)and eventually gaseous CH4. The ZnO nanoplates, exposing a higher fraction of Zn-ZnO(0001) and OZnO(000–1) polar facets, are more active than the ZnO powders to catalyze CO hydrogenation to CH4.These results provide fundamental understanding of the reaction mechanisms and structural effects of CO hydrogenation reaction catalyzed by ZnO-based catalysts.展开更多
Taking isovanillin and the important products synthesized from raw materials of isovanillin as objects,this paper reviews its pharmacological effects and molecular mechanisms,including inhibiting tumor angiogenesis,bl...Taking isovanillin and the important products synthesized from raw materials of isovanillin as objects,this paper reviews its pharmacological effects and molecular mechanisms,including inhibiting tumor angiogenesis,blocking cancer cell self-repair,inducing cancer cell DNA fragmentation,cytotoxicity,inhibiting tumor growth,regulating brain nerves,inhibiting renin and other pharmacological effects,etc.,which provide new ideas for the in-depth research and development of isovanillin.展开更多
基金financially supported by the National Natural Science Foundation of China, China (21922803, 22122807, and 22008072)the Innovation Program of Shanghai Municipal Education Commission, China+1 种基金the Program of Shanghai Academic/Technology Research Leader, China (21XD1421000)the China Postdoctoral Science Foundation, China (2020M671025 and 2019TQ0093)。
文摘Mechanistic understanding of the active intermediates of 2,6-diaminopyridine(DAP) dinitration in the concentrated nitric-sulfuric acid system is of crucial importance for the selectivity control of target product, i.e., 2,6-diamino-3,5-dinitropyridine(DADNP). The active intermediates determining the product selectivity are theoretically studied. The HSO_(4)^(-)-NO_(2)^(+) complex is proposed as the dominant active nitrating intermediate for the first time, which shows low energy barrier(i.e., 10.19 kcal·mol^(-1),1 kcal = 4.186 k J) for direct dinitration of DAP to DADNP. The formed water during the reaction results in not only the formation of less active SO_(4)^(2-)-NO_(2)^(+) complex, but also the occurance of DAP sulfonation(DAP-SO_(3)H intermediate)to facilitate the formation of mononitration byproduct. Meanwhile, the accompanied thermal effects cause the generation of undesirable pyridine-NHNO_(2) intermediate, which is difficult to be rearranged to yield DADNP, inhibiting the reaction and thus giving low DAP conversion. The insights reported here elucidates the importance of thermal effects elimination and water content control, confirmed experimentally in the batch-and micro-reaction systems.
文摘Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium geometries including comparing to the AE-active ester. It was found that the Ethyl-aminothiazoly Loximate (AT) molecule fragment is almost planar sheet, but it is almost perpendicular to the plane of phosphoryl ester. Moreover, the calculated Mulliken atomic charge distribution and frontier molecular orbital analysis of these esters showed that the amino N atom connected to the Thiazole ring of the AT had the maximum negative charge, which suggested that this area had high molecular activity. The value of ΔEL-H was energy gap between EHOMO and ELUMO and indicated that compound 6a had high reaction activity. The theory calculation results can explain the reaction mechanism well and predict that the novel active phosphonate ester has a hopeful application prospect in preparation of Cephalosporin antibiotics’ intermediate.
文摘Excessive nitrate in groundwater has emerged as a serious environmental concern. The elevated nitrate concentration in drinking water causes a serious threat to public health on account of the possible transformation of nitrate to nitrite, which is one of the main predisposing factors of methemoglobinemia [1].
文摘Prostate cancer is the leading male cancer worldwide. There remains a controversy as to which patients have indolent disease and which patients present an aggressive disease needing treatment with intent to cure. Because of quality of life impairment associated with treatment by radiation or surgery, active surveillance (AS) is a valid management option to avoid or differ aggressive treatment. Traditionally, AS was reserved for men with low risk prostate cancer, however intermediate risk patients are more and more found in AS cohorts. The aim of this review is to describe the place of AS in intermediate risk patients and the perspectives offered by such a treatment modality.
基金supported by grants from the National Natural Science Foundation of China (No. 81072001)the Natural Science Foundation of Hubei Province, China (No.2011CDB556)
文摘The roles of intermediate conductance Ca2＋-activated K＋ channel （IKCal） in the pathogene- sis of hepatocellular carcinoma （HCC） were investigated. Immunohistochemistry and Western blotting were used to detect the expression of IKCal protein in 50 HCC and 20 para-carcinoma tissue samples. Real-time PCR was used to detect the transcription level of IKCal mRNA in 13 HCC and 11 para-carcinoma tissue samples. The MTT assay was used to measure the function of IKCal in human HCC cell line HepG2 in vitro. TRAM-34, a specific blocker of IKCal, was used to intervene with the function of IKCal. As compared with para-carcinoma tissue, an over-expression of IKCal protein was detected in HCC tissue samples （P〈0.05）. The mRNA expression level of IKCal in HCC tissues was 2.17 times higher than that in para-carcinoma tissues. The proliferation of HepG2 cells was suppressed by TRAM-34 （0.5, 1.0, 2.0 and 4.0 pxnol/L） in vitro （P〈0.05）. Our results suggested that IKCal may play a role in the proliferation of human HCC, and IKCal blockers may represent a potential therapeutic strategy for HCC.
基金financial support from DICP and K.C.Wong Education Foundation(GJTD-2020-08).
文摘Palladium-catalyzed carbonylation is an efficient approach to prepare carbonyl-containing compounds with high atomic economy in synthetic organic chemistry.However,in comparison with aryl halides,carbonylation of alkyl halides is relatively challenging due to the decreased stability of the palladium intermediates.Carbonylation of activated alkyl halides is even more difficult,as nucleophilic substitution reactions with nucleophiles occur more easily with them.In this article,we summarize and discuss recent achievements in palladium-catalyzed carbonylative reactions of activated alkyl halides.The transformations proceed through radical intermediates which are generated in various manners.Under a relatively high pressure of carbon monoxide,the corresponding aliphatic carboxylic acid derivates were effectively prepared with various nucleophiles as the reaction partners.Besides alcohols,amines and organoboron reagents,four-component reactions in combination with alkenes or alkynes were also developed.Case-by-case reaction mechanisms are discussed as well and a personal outlook has also been provided.
基金Supported by the National Natural Science Foundation of China (No. 20176047)
文摘The Ti/SnO2+Sb2O3/PbO2 anode with SnO2+Sb2O3 intermediate layer obtained by the polymeric precursor method (PPM) and with the conventional route was studied. The morphology and microstructure of SnO2+Sb2O3 intermediate layer derived from different precursors and the top PbO2 active layer were examined by means of ESEM and XRD. The lifetime and electrocatalytic activity of the anode were also assessed by the cyclic voltammetry and accelerated lifetime test in 1.0 mol/L H2SO4 solution. It was found that precursor solvents affected lifetime, microstructure and morphology of the anode, and had little influence on electrocatalysis activity of the electrodes. The accelerated lifetime of Ti/SnO2+Sb2O3/PbO2 anode with intermediate layer prepared by PPM was 29.5 h in 1.0 mol/L H2SO4 solution, which was respectively about four times and twice that of the anode prepared with ethylene glycol and ethanol. After the anode was subjected to thermal corrosion, the lifetime still reached 27 h in contrast to the others.
基金the National Key R&D Program of Ministry of Science and Technology of China(2017YFB0602205)the National Natural Science Foundation of China(21525313,91745202,91945301)+4 种基金the Chinese Academy of Sciencesthe Changjiang Scholars Program of Ministry of Education of Chinathe financial support of the China Scholarship Councilsupported by the Scientific User Facilities Division,Office of Basic Energy Sciences,US DOE,under Contract No.DE-AC0500OR22725 with UT Battelle,LLCsupported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Chemical Sciences,Geosciences,and Biosciences Division,Catalysis Science Program。
文摘Activation and surface reactions of CO and H2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions were(quasi) in situ studied using temperature programmed surface reaction spectra, diffuse reflectance Fourier transform infrared spectroscopy, inelastic neutron scattering spectroscopy and electron paramagnetic resonance. CO undergoes disproportion reaction to produce gaseous CO2 and surface carbon adatoms, and adsorbs to form surface formate species. H2 adsorption forms dominant irreversibly-adsorbed surface hydroxyl groups and interstitial H species and very minor surface Zn-H species. Surface formate species and hydroxyl groups react to produce CO2 and H2, while surface carbon adatoms are hydrogenated by surface Zn-H species sequentially to produce CH(a), CH2(a), CH3(a)and eventually gaseous CH4. The ZnO nanoplates, exposing a higher fraction of Zn-ZnO(0001) and OZnO(000–1) polar facets, are more active than the ZnO powders to catalyze CO hydrogenation to CH4.These results provide fundamental understanding of the reaction mechanisms and structural effects of CO hydrogenation reaction catalyzed by ZnO-based catalysts.
基金Supported by the Central Talent Training Fund for Local University Reform and Development(2020GSP16).
文摘Taking isovanillin and the important products synthesized from raw materials of isovanillin as objects,this paper reviews its pharmacological effects and molecular mechanisms,including inhibiting tumor angiogenesis,blocking cancer cell self-repair,inducing cancer cell DNA fragmentation,cytotoxicity,inhibiting tumor growth,regulating brain nerves,inhibiting renin and other pharmacological effects,etc.,which provide new ideas for the in-depth research and development of isovanillin.
