Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated ...Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.展开更多
The catalytic performance of a series of cobalt(Ⅱ) hydroxamates (CoL2) and the synergistic catalytic action of the cobalt complexes combined with N-hydroxyphthalimide (NHPI) in the aerobic oxidation of p-xylene to p-...The catalytic performance of a series of cobalt(Ⅱ) hydroxamates (CoL2) and the synergistic catalytic action of the cobalt complexes combined with N-hydroxyphthalimide (NHPI) in the aerobic oxidation of p-xylene to p-toluic acid (PTA) were investigated. The results showed that the existing synergistic action in the catalytic oxidation can shorten the induction period of the radical reaction and improve the yield of PTA.展开更多
AIM: To investigate the role of oxidative injury and the effect of exogenous melatonin administration on liver damage induced by bile duct ligation (BDL), and second, to evaluate the role of nitric oxide (NO), a free ...AIM: To investigate the role of oxidative injury and the effect of exogenous melatonin administration on liver damage induced by bile duct ligation (BDL), and second, to evaluate the role of nitric oxide (NO), a free oxygen radical, in oxidative injury. METHODS: Thirty-two Sprague-Dawley rats were assigned to four groups: sham operation (SO), BDL, BDL+melatonin, and BDL+vehicle. Cholestasis was achieved by double ligature of the common bile duct. Melatonin was injected intraperitoneally 500 μg/(kg·d) for 8 d. Hepatic oxidative stress markers were evaluated by changes in the amount of lipid peroxides, measured as malondialdehyde (MDA), and reduced GSH. Total nitrite (NOx) concentrations were determined in hepatic homogenates. Histopathological examination was performed using a histological scoring system. RESULTS: The histopathological changes including portal inflammation, necrosis,apoptosis, focal inflammation and fibrosis were severe in the BDL and BDL+vehicle groups. There were numerous large areas of coagulation necrosis. Histological Activity Index scores of these groups were significantly higher than that of the SO group. Treatment with melatonin reduced these alterations significantly. The degree of necro-inflammation and fibrosis showed significant difference between the BDL and BDL+melatonin groups. BDL was accompanied by a significant increase in MDA and NOx, and a significant decrease in GSH levels. Mean±SE values of MDA, GSH and NOx levels of SO group were 147.47±6.69, 0.88±0.33 μmol/g and 180.70±6.58 nm/g, respectively. The values of BDL group were 200.14±21.30, 0.65±0.02 μmol/g, and 400.46±48.89 nm/g, respectively, whereas the values of BDL+melatonin group were 115.93±6.8,0.74±0.02 μmol/g, and 290.38±32.32 nm/g, respectively. Melatonin treatment was associated with a significant recovery of MDA, GSH and NOx levels. CONCLUSION: We have concluded that oxidative stress is associated with the pathogenesis of cholestatic liver damage and NO contributes to oxidative damage. Melatonin, even at low dose, is an efficient agent in reducing negative parameters of cholestasis.展开更多
Selective oxidation with molecular oxygen as the sole oxidant under mild conditions is of crucialimportance for the long‐term sustainable exploitation of available feedstocks and the formation ofrequired intermediate...Selective oxidation with molecular oxygen as the sole oxidant under mild conditions is of crucialimportance for the long‐term sustainable exploitation of available feedstocks and the formation ofrequired intermediates for organic synthesis and industrial processes.Among the developed oxidationprotocols,innovative strategies using hydroxyimide organocatalysts in combination with metallicor metal‐free cocatalysts have attracted much attention because of the good activities andselectivities of such catalysts in the oxo functionalization of hydrocarbons.This method is based onthe reaction using N‐hydroxyphthalimide,which was first reported by Ishii’s group in the1990s.Although the important and wide‐ranging applications of such catalysts have been summarizedrecently,there are no reviews that focus solely on oxidation strategies using multi‐nitroxy organocatalysts,which have interesting properties and high reactivities.This review covers the concisesynthetic methods and mechanistic profiles of known multi‐nitroxy organocatalysts and summarizessignificant advances in their use in efficient aerobic oxidation.Based on a combination of experimentaland theoretical results,guidelines for the future rational design of multi‐nitroxy organocatalystsare proposed,and the properties of various model multi‐nitroxy organocatalysts are predicted.The present overview of the advantages,limitations,and potential applications of multi‐nitroxyorganocatalysts can provide useful tools for researchers in the field of selective oxidation.展开更多
In this article, we have performed B3LYP/6-31＋G（d） calculations of geometrical and reaction enthalpies of antioxidant mechanisms for ADPHT 1-4 （3-alkyl-4-phenylacetylamino-lH-1,2,4-triazol-5-ones） and its derivat...In this article, we have performed B3LYP/6-31＋G（d） calculations of geometrical and reaction enthalpies of antioxidant mechanisms for ADPHT 1-4 （3-alkyl-4-phenylacetylamino-lH-1,2,4-triazol-5-ones） and its derivatives： HAT （hydrogen atom transfer）, SET-PT （single electron transfer-proton transfer） and SPLET （sequential proton-loss electron transfer） were investigated in gas and solution-phases. Solvent contribution to enthalpies was computed employing integral equation formalism IEF-PCM （integral equation formalism method） method. It turned out that the lowest BDEs （bond dissociation energies） is obtained for C-H bonds due to captodative effect in various media. Results indicate that HAT mechanism represents the most anticipated process in gas-phase from thermodynamic point of view. But, the SPLET represents the thermodynamically preferred reaction pathway in solvents （2-propanol, acetonitrile, DMF （N,N-dimethylformamide） and water）. The authors showed that bond dissociation energies, IP （ionization potential） and PA （proton affinity） are sufficient to evaluate the thermodynamically preferred mechanism.展开更多
A novel phthalocyanine, 2,9（10）,16（17）,23（24）-tetra（4-benzoyl）phenoxyphthalocyanine, and its complexes with Zn（Ⅱ）, Cu（Ⅱ）, Co（Ⅱ）, and Ni（Ⅱ） have been synthesized and characterized by a combination o...A novel phthalocyanine, 2,9（10）,16（17）,23（24）-tetra（4-benzoyl）phenoxyphthalocyanine, and its complexes with Zn（Ⅱ）, Cu（Ⅱ）, Co（Ⅱ）, and Ni（Ⅱ） have been synthesized and characterized by a combination of elemental analysis, IR, IH NMR, UV-vis spectroscopy and mass spectrometry. All of the materials are very soluble in common organic solvents such as dichloro- methane, chloroform, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide. The Q band wavelengths of the com- plexes decrease in the order： Zn 〉 Cu 〉 Ni 〉 Co. Redox processes were observed at -1.06, -0.74, 0.51 and 0.98 V for the free phthalocyanine, at -0.72 and 1.04 V for the Co（Ⅱ） complex, at -1.24, -0.77, -0.24, 0.61 and 0,91 V for the Cu（Ⅱ） complex, and at -0.74 and 1.20 V for the Ni（Ⅱ） complex. The cyclic voltammograms of the phthalocyanine ring of the four species are similar, with reduction and oxidation couples each involving a one-electron transfer process.展开更多
基金supported by Shanghai Municipal Natural Science Foundation,China(15ZR1447800)the Chinese Postdoctoral Science Foundation(2012M511158,2013T60477,2014M560363)~~
文摘Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.
基金supported by the National Natural Science Foundation of China(Grant No.20072025).
文摘The catalytic performance of a series of cobalt(Ⅱ) hydroxamates (CoL2) and the synergistic catalytic action of the cobalt complexes combined with N-hydroxyphthalimide (NHPI) in the aerobic oxidation of p-xylene to p-toluic acid (PTA) were investigated. The results showed that the existing synergistic action in the catalytic oxidation can shorten the induction period of the radical reaction and improve the yield of PTA.
文摘AIM: To investigate the role of oxidative injury and the effect of exogenous melatonin administration on liver damage induced by bile duct ligation (BDL), and second, to evaluate the role of nitric oxide (NO), a free oxygen radical, in oxidative injury. METHODS: Thirty-two Sprague-Dawley rats were assigned to four groups: sham operation (SO), BDL, BDL+melatonin, and BDL+vehicle. Cholestasis was achieved by double ligature of the common bile duct. Melatonin was injected intraperitoneally 500 μg/(kg·d) for 8 d. Hepatic oxidative stress markers were evaluated by changes in the amount of lipid peroxides, measured as malondialdehyde (MDA), and reduced GSH. Total nitrite (NOx) concentrations were determined in hepatic homogenates. Histopathological examination was performed using a histological scoring system. RESULTS: The histopathological changes including portal inflammation, necrosis,apoptosis, focal inflammation and fibrosis were severe in the BDL and BDL+vehicle groups. There were numerous large areas of coagulation necrosis. Histological Activity Index scores of these groups were significantly higher than that of the SO group. Treatment with melatonin reduced these alterations significantly. The degree of necro-inflammation and fibrosis showed significant difference between the BDL and BDL+melatonin groups. BDL was accompanied by a significant increase in MDA and NOx, and a significant decrease in GSH levels. Mean±SE values of MDA, GSH and NOx levels of SO group were 147.47±6.69, 0.88±0.33 μmol/g and 180.70±6.58 nm/g, respectively. The values of BDL group were 200.14±21.30, 0.65±0.02 μmol/g, and 400.46±48.89 nm/g, respectively, whereas the values of BDL+melatonin group were 115.93±6.8,0.74±0.02 μmol/g, and 290.38±32.32 nm/g, respectively. Melatonin treatment was associated with a significant recovery of MDA, GSH and NOx levels. CONCLUSION: We have concluded that oxidative stress is associated with the pathogenesis of cholestatic liver damage and NO contributes to oxidative damage. Melatonin, even at low dose, is an efficient agent in reducing negative parameters of cholestasis.
基金supported by the China Postdoctoral Science Foundation (2014M551746)~~
文摘Selective oxidation with molecular oxygen as the sole oxidant under mild conditions is of crucialimportance for the long‐term sustainable exploitation of available feedstocks and the formation ofrequired intermediates for organic synthesis and industrial processes.Among the developed oxidationprotocols,innovative strategies using hydroxyimide organocatalysts in combination with metallicor metal‐free cocatalysts have attracted much attention because of the good activities andselectivities of such catalysts in the oxo functionalization of hydrocarbons.This method is based onthe reaction using N‐hydroxyphthalimide,which was first reported by Ishii’s group in the1990s.Although the important and wide‐ranging applications of such catalysts have been summarizedrecently,there are no reviews that focus solely on oxidation strategies using multi‐nitroxy organocatalysts,which have interesting properties and high reactivities.This review covers the concisesynthetic methods and mechanistic profiles of known multi‐nitroxy organocatalysts and summarizessignificant advances in their use in efficient aerobic oxidation.Based on a combination of experimentaland theoretical results,guidelines for the future rational design of multi‐nitroxy organocatalystsare proposed,and the properties of various model multi‐nitroxy organocatalysts are predicted.The present overview of the advantages,limitations,and potential applications of multi‐nitroxyorganocatalysts can provide useful tools for researchers in the field of selective oxidation.
文摘In this article, we have performed B3LYP/6-31＋G（d） calculations of geometrical and reaction enthalpies of antioxidant mechanisms for ADPHT 1-4 （3-alkyl-4-phenylacetylamino-lH-1,2,4-triazol-5-ones） and its derivatives： HAT （hydrogen atom transfer）, SET-PT （single electron transfer-proton transfer） and SPLET （sequential proton-loss electron transfer） were investigated in gas and solution-phases. Solvent contribution to enthalpies was computed employing integral equation formalism IEF-PCM （integral equation formalism method） method. It turned out that the lowest BDEs （bond dissociation energies） is obtained for C-H bonds due to captodative effect in various media. Results indicate that HAT mechanism represents the most anticipated process in gas-phase from thermodynamic point of view. But, the SPLET represents the thermodynamically preferred reaction pathway in solvents （2-propanol, acetonitrile, DMF （N,N-dimethylformamide） and water）. The authors showed that bond dissociation energies, IP （ionization potential） and PA （proton affinity） are sufficient to evaluate the thermodynamically preferred mechanism.
基金supported by the Application Foundation of the Science and Technology Office of Jilin Province (20080901)the Fundamental Research Funds for the Central Universities (09SSXT030)
文摘A novel phthalocyanine, 2,9（10）,16（17）,23（24）-tetra（4-benzoyl）phenoxyphthalocyanine, and its complexes with Zn（Ⅱ）, Cu（Ⅱ）, Co（Ⅱ）, and Ni（Ⅱ） have been synthesized and characterized by a combination of elemental analysis, IR, IH NMR, UV-vis spectroscopy and mass spectrometry. All of the materials are very soluble in common organic solvents such as dichloro- methane, chloroform, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide. The Q band wavelengths of the com- plexes decrease in the order： Zn 〉 Cu 〉 Ni 〉 Co. Redox processes were observed at -1.06, -0.74, 0.51 and 0.98 V for the free phthalocyanine, at -0.72 and 1.04 V for the Co（Ⅱ） complex, at -1.24, -0.77, -0.24, 0.61 and 0,91 V for the Cu（Ⅱ） complex, and at -0.74 and 1.20 V for the Ni（Ⅱ） complex. The cyclic voltammograms of the phthalocyanine ring of the four species are similar, with reduction and oxidation couples each involving a one-electron transfer process.
