The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Gerald Pattenden - One of the best experts on this subject based on the ideXlab platform.
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total synthesis of phorboxazole a a potent cytostatic agent from the sponge phorbas sp
Organic and Biomolecular Chemistry, 2003Co-Authors: Gerald Pattenden, Miguel Gonzalez, Paul Brian Little, David S Millan, Alleyn T Plowright, James A TornosAbstract:A convergent total synthesis of phorboxazole A (1a), from the C(3–19), C(20–27) and C(33–46) fragments 5, 4 and 91, respectively, concentrating on stereocontrolled formation of the bonds at C(2–3), C(19–20) and C(27–28), is described. Although a coupling reaction between a macrolide ketone and the side chain substituted sulfone, at C(27–28) was not successful, a Wadsworth–Emmons olefination involving the Oxane methyl ketone 4 and an oxazole produced the Oxane 90 which was next coupled to 91 leading to the C(20–46) unit 100. A further coupling of 100 to 71c at C(19–20) then led to 105, ultimately, and the synthesis was completed by a macrocyclisation reaction from 105, at the C(2–3) alkene bond, followed by deprotection of 106.
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synthetic studies towards phorboxazole a stereoselective synthesis of the c3 c19 bis Oxane oxazole portion of the phorboxazole macrolide
Tetrahedron Letters, 2000Co-Authors: Gerald Pattenden, Alleyn T PlowrightAbstract:Abstract A synthesis of the C3–C19 bis-Oxane portion of phorboxazole A, involving an oxy anion intramolecular Michael reaction to produce a cis -Oxane and an intramolecular Williamson reaction leading to a trans -Oxane, is described.
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synthetic studies towards phorboxazole a a convergent synthesis of the c31c46 polyene Oxane hemiacetal side chain
Tetrahedron Letters, 1998Co-Authors: Gerald Pattenden, Alleyn T Plowright, James A TornosAbstract:Abstract A convergent and stereoselective synthesis of the C31C46 side chain unit in the marine natural product phorboxazole A, which accommodates five asymmetric centres, three carbon-to-carbon double bonds and an Oxane-hemiacetal unit, is described.
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synthetic studies towards phorboxazole a a concise stereoselective synthesis of the c20c26 pentasubstituted Oxane ring unit
Tetrahedron Letters, 1998Co-Authors: Gerald PattendenAbstract:Abstract A stereoselective synthesis of the 2,6-cis Oxane unit, accommodating five contiguous asymmetric centres, found in the novel marine natural product phorboxazole A 1, is described.
Alleyn T Plowright - One of the best experts on this subject based on the ideXlab platform.
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total synthesis of phorboxazole a a potent cytostatic agent from the sponge phorbas sp
Organic and Biomolecular Chemistry, 2003Co-Authors: Gerald Pattenden, Miguel Gonzalez, Paul Brian Little, David S Millan, Alleyn T Plowright, James A TornosAbstract:A convergent total synthesis of phorboxazole A (1a), from the C(3–19), C(20–27) and C(33–46) fragments 5, 4 and 91, respectively, concentrating on stereocontrolled formation of the bonds at C(2–3), C(19–20) and C(27–28), is described. Although a coupling reaction between a macrolide ketone and the side chain substituted sulfone, at C(27–28) was not successful, a Wadsworth–Emmons olefination involving the Oxane methyl ketone 4 and an oxazole produced the Oxane 90 which was next coupled to 91 leading to the C(20–46) unit 100. A further coupling of 100 to 71c at C(19–20) then led to 105, ultimately, and the synthesis was completed by a macrocyclisation reaction from 105, at the C(2–3) alkene bond, followed by deprotection of 106.
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synthetic studies towards phorboxazole a stereoselective synthesis of the c3 c19 bis Oxane oxazole portion of the phorboxazole macrolide
Tetrahedron Letters, 2000Co-Authors: Gerald Pattenden, Alleyn T PlowrightAbstract:Abstract A synthesis of the C3–C19 bis-Oxane portion of phorboxazole A, involving an oxy anion intramolecular Michael reaction to produce a cis -Oxane and an intramolecular Williamson reaction leading to a trans -Oxane, is described.
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synthetic studies towards phorboxazole a a convergent synthesis of the c31c46 polyene Oxane hemiacetal side chain
Tetrahedron Letters, 1998Co-Authors: Gerald Pattenden, Alleyn T Plowright, James A TornosAbstract:Abstract A convergent and stereoselective synthesis of the C31C46 side chain unit in the marine natural product phorboxazole A, which accommodates five asymmetric centres, three carbon-to-carbon double bonds and an Oxane-hemiacetal unit, is described.
Baoling Yuan - One of the best experts on this subject based on the ideXlab platform.
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modulating oxone mnox silica catalytic systems towards ibuprofen degradation insights into system effects reaction kinetics and mechanisms
Applied Catalysis B-environmental, 2017Co-Authors: Jiacheng E Yang, Baoling Yuan, Haojie Cui, Shaobin WangAbstract:Abstract Heterogeneous processes activated persulfate for organic degradation is increasingly recognized as an environmentally important remediation technology. However, manipulating persulfate oxidation processes with desirable decontamination effectiveness is still underdeveloped. Towards this goal, we systematically investigated the catalytic behaviors of Oxone-MnO x /silica systems towards aqueous ibuprofen (IBU) degradation in terms of system effects, reaction kinetics and mechanisms. MnO x /SBA-15 (MS) demonstrated variable catalytic Oxone efficacies towards IBU removal at different solution pHs. Meanwhile, the catalyst supports and FeO x co-doping within MS also produced significant impacts on catalytic Oxone efficacy. Moreover, the catalytic Oxone efficacies of MS for IBU degradation were generally inhibited by humic acid, NO 3 − , HCO 3 − , SO 4 2− and PO 4 3− to different extents at low/high levels. Interestingly, Cl − at low concentrations (2 mM) obviously inhibited IBU removal by Oxone-MS, while Cl − at high concentrations (20 mM) greatly enhanced IBU removal. Kinetic studies implied that IBU removal by Oxone-MnO x /silica systems using two first-order kinetic models was closely related to the extents of the interferences of synthetic conditions and water chemistry components. The surface electron transfer between MnO x (OH) y species of MS and HSO 5 − of Oxone was responsible for the formation of reactive oxygen radicals, thus contributing to IBU degradation. Liquid chromatography–mass spectrometry was employed to identify oxidation products of IBU, and reaction pathways of IBU oxidation were accordingly proposed.
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synthetic conditions regulated catalytic oxone efficacy of mnox sba 15 towards butyl paraben bpb removal under heterogeneous conditions
Chemical Engineering Journal, 2016Co-Authors: Jiacheng E Yang, Huachun Lan, Xiaoqiong Lin, Baoling YuanAbstract:Abstract Heterogeneous catalysts prepared under different conditions usually demonstrate different catalytic performance, but the underlying influences are not well addressed. Therefore, MnOx/SBA-15 (MS) composites were fabricated under different synthetic conditions to probe the links between their changes in physicochemical features and catalytic Oxone efficacies, using butyl paraben (BPB) as a probe chemical. Characterization results demonstrated that the changes of Mn/SBA-15 weight ratio, calcination temperature and time altered the physic–chemical characteristics of MS composites such as the specific surface area and the types/amounts of MnOx species of MS composites. Further studies showed that these synthetic conditions had affected the catalytic Oxone performance of MS composites towards BPB removal through changing the types or the amounts of active radicals. The catalytic Oxone efficacy of the optimized MS was highly dependent on the changes of the dosages of MS and Oxone and the initial pH values of BPB solutions. SO4 − and OH were identified as the main reactive species of MS–Oxone system responsible for BPB removal. Additionally, the thermally activated MS demonstrated excellent catalytic Oxone efficacy during its recycles. These findings will increase the knowledge regarding the “synthetic conditions – physicochemical characteristics – application” centered-relationships of heterogeneous catalysts for water treatment.
Wei Chu - One of the best experts on this subject based on the ideXlab platform.
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photo assisted degradation of 2 4 5 trichlorophenoxyacetic acid by fe ii catalyzed activation of oxone process the role of uv irradiation reaction mechanism and mineralization
Applied Catalysis B-environmental, 2012Co-Authors: Yr R Wang, Wei ChuAbstract:In this study, the potential of Fe(II)-catalyzed activation of Oxone process with UV irradiation (FOU) for the degradation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in aqueous solution was explored and compared with the Fe(II)/Oxone (FO) process. Experimental results show that the FO process was dramatically promoted upon the introduction of UV irradiation. As a result, the role of UV irradiation was elucidated in-depth by comparing the real-time of [Fe(II)] between the FO process and the FOU process. It was found that a beneficial Fe(III)/Fe(II) catalytic cycle is established in the presence of UV irradiation, thereby leading to the accelerated regeneration of Fe(II). Additionally, 2,4,5-T decay by the FOU process under various [Oxone] and [2,4,5-T] was also examined. Furthermore, the decay pathways for the transformation of 2,4,5-T by UV alone, Oxone/UV, and FOU processes were proposed by using LC-ESI/MS analysis. Distinct differences of intermediate distributions were observed among the three processes with or without the involvement of radicals (OH and SO4−). Besides, the efficiencies of various processes (i.e., UV alone, Oxone/UV and FOU) were further examined in terms of mineralization and Cl− ion accumulation.
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degradation of 2 4 5 trichlorophenoxyacetic acid by a novel electro fe ii oxone process using iron sheet as the sacrificial anode
Water Research, 2011Co-Authors: Yuru Wang, Wei ChuAbstract:A novel electrochemically enhanced advanced oxidation process for the destruction of organic contaminants in aqueous solution is reported in this study. The process involves the use of an iron (Fe) sheet as sacrificial anode and a graphite bar as cathode. In the oxidation process, once an electric current is applied between the anode and the cathode, a predetermined amount of Oxone is added to the reactor. Ferrous ions generated from the sacrificed Fe anode mediate the generation of highly powerful radicals (SO(4)(•-)) through the decomposition of Oxone. The coupled process of Fe(II)/Oxone and electrochemical treatment (Electro-Fe(II)/Oxone) was evaluated in terms of 2,4,5-Trichlorophenoxyacetic acid degradation in aqueous solution. Various parameters were investigated to optimize the process, including applied current, electrolyte and Oxone concentration. In addition, low solution pH facilitates the system performance due to the dual effects of weak Fenton reagent generation and persulfate ions generation, whereas the system performance was inhibited at basic pH levels through non-radical self-dissociation of Oxone and the formation of ferric hydroxide precipitates. Furthermore, the active radicals involved in the Electro-Fe(II)/Oxone process were also identified. The Electro-Fe(II)/Oxone process demonstrates a very high 2,4,5-T degradation efficiency (over 90% decay within 10 min), which justifies the novel Electro-Fe(II)/Oxone a promising treatment process for herbicide removal in water.
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degradation of a xanthene dye by fe ii mediated activation of oxone process
Journal of Hazardous Materials, 2011Co-Authors: Yuru Wang, Wei ChuAbstract:Abstract A powerful oxidation process using sulfate radicals activated by transition metal mediated Oxone process has been evaluated in depth by monitoring the degradation of a xanthene dye Rhodamine B (RhB) in aqueous solution. Ferrous ion was chosen as the transition metal due to its potential catalytic effect and wide availability in dyeing industrial effluent. The effects of parameters including reactant dosing sequence, Fe(II)/Oxone molar ratio and concentration, solution pH, and inorganic salts on the process performance have been investigated. Total RhB removal was obtained within 90 min under an optimal Fe(II)/Oxone molar ratio of 1:1. The RhB degradation was found to be a two-stage kinetics, consisting of a rapid initial decay and followed by a retarded stage. Additionally, experimental results indicated that the presence of certain anions had either a positive or negative effect on the process. The inhibitory effect in the presence of SO42− was elucidated by a proposed formula using Nernst equation. Furthermore, dye mineralization in terms of TOC removal indicates that stepwise addition of Fe(II) and Oxone can significantly improve the process performance by about 20%, and the retention time required can be greatly reduced comparing with the conventional one-off dosing method.
Jiacheng E Yang - One of the best experts on this subject based on the ideXlab platform.
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modulating oxone mnox silica catalytic systems towards ibuprofen degradation insights into system effects reaction kinetics and mechanisms
Applied Catalysis B-environmental, 2017Co-Authors: Jiacheng E Yang, Baoling Yuan, Haojie Cui, Shaobin WangAbstract:Abstract Heterogeneous processes activated persulfate for organic degradation is increasingly recognized as an environmentally important remediation technology. However, manipulating persulfate oxidation processes with desirable decontamination effectiveness is still underdeveloped. Towards this goal, we systematically investigated the catalytic behaviors of Oxone-MnO x /silica systems towards aqueous ibuprofen (IBU) degradation in terms of system effects, reaction kinetics and mechanisms. MnO x /SBA-15 (MS) demonstrated variable catalytic Oxone efficacies towards IBU removal at different solution pHs. Meanwhile, the catalyst supports and FeO x co-doping within MS also produced significant impacts on catalytic Oxone efficacy. Moreover, the catalytic Oxone efficacies of MS for IBU degradation were generally inhibited by humic acid, NO 3 − , HCO 3 − , SO 4 2− and PO 4 3− to different extents at low/high levels. Interestingly, Cl − at low concentrations (2 mM) obviously inhibited IBU removal by Oxone-MS, while Cl − at high concentrations (20 mM) greatly enhanced IBU removal. Kinetic studies implied that IBU removal by Oxone-MnO x /silica systems using two first-order kinetic models was closely related to the extents of the interferences of synthetic conditions and water chemistry components. The surface electron transfer between MnO x (OH) y species of MS and HSO 5 − of Oxone was responsible for the formation of reactive oxygen radicals, thus contributing to IBU degradation. Liquid chromatography–mass spectrometry was employed to identify oxidation products of IBU, and reaction pathways of IBU oxidation were accordingly proposed.
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synthetic conditions regulated catalytic oxone efficacy of mnox sba 15 towards butyl paraben bpb removal under heterogeneous conditions
Chemical Engineering Journal, 2016Co-Authors: Jiacheng E Yang, Huachun Lan, Xiaoqiong Lin, Baoling YuanAbstract:Abstract Heterogeneous catalysts prepared under different conditions usually demonstrate different catalytic performance, but the underlying influences are not well addressed. Therefore, MnOx/SBA-15 (MS) composites were fabricated under different synthetic conditions to probe the links between their changes in physicochemical features and catalytic Oxone efficacies, using butyl paraben (BPB) as a probe chemical. Characterization results demonstrated that the changes of Mn/SBA-15 weight ratio, calcination temperature and time altered the physic–chemical characteristics of MS composites such as the specific surface area and the types/amounts of MnOx species of MS composites. Further studies showed that these synthetic conditions had affected the catalytic Oxone performance of MS composites towards BPB removal through changing the types or the amounts of active radicals. The catalytic Oxone efficacy of the optimized MS was highly dependent on the changes of the dosages of MS and Oxone and the initial pH values of BPB solutions. SO4 − and OH were identified as the main reactive species of MS–Oxone system responsible for BPB removal. Additionally, the thermally activated MS demonstrated excellent catalytic Oxone efficacy during its recycles. These findings will increase the knowledge regarding the “synthetic conditions – physicochemical characteristics – application” centered-relationships of heterogeneous catalysts for water treatment.
