15 results on '"Ruibo Li"'
Search Results
2. Palladium-Catalyzed Allenamide Carbopalladation/Allylation with Active Methine Compounds
- Author
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Aijun Lin, Hequan Yao, Xiaoyi Zhu, and Ruibo Li
- Subjects
010405 organic chemistry ,Organic Chemistry ,chemistry.chemical_element ,Substrate (chemistry) ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,Oxidative addition ,0104 chemical sciences ,Catalysis ,Tsuji–Trost reaction ,chemistry.chemical_compound ,chemistry ,Functional group ,Physical and Theoretical Chemistry ,Palladium ,Quaternary carbon - Abstract
A palladium-catalyzed allenamide carbopalladation/allylation with active methine compounds has been developed. Various indoles and isoquinolinones bearing a quaternary carbon center were achieved with good efficiency, a broad substrate scope and good functional group tolerance. This reaction underwent cascade oxidative addition, carbopalladation, and allylic alkylation, and two new C-C bonds were formed in one pot.
- Published
- 2021
3. Alkyl β-D-xyloside synthesis from black liquor xylan using Aureobasidium pullulans CBS 135684 β-xylosidases immobilized on spent expanded perlite
- Author
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Hunsa Punnapayak, Sehanat Prasongsuk, Dede Heri Yuli Yanto, Pongtharin Lotrakul, Takashi Watanabe, Ruibo Li, and Wichanee Bankeeree
- Subjects
chemistry.chemical_classification ,Immobilized enzyme ,biology ,Renewable Energy, Sustainability and the Environment ,020209 energy ,02 engineering and technology ,010501 environmental sciences ,biology.organism_classification ,01 natural sciences ,Xylan ,Hydrolysate ,Xyloside ,Aureobasidium pullulans ,chemistry.chemical_compound ,Glucoside ,chemistry ,0202 electrical engineering, electronic engineering, information engineering ,Alkyl ,0105 earth and related environmental sciences ,Nuclear chemistry ,Hexanol - Abstract
The crude β-xylosidase from Aureobasidium pullulans CBS 135684 was immobilized on the surface of the modified spent expanded perlite via (3-aminopropyl) triethoxy-silane and glutaraldehyde cross-linking reaction. Over 80% of the initial free enzyme activity was detected on the bound enzyme. The immobilized β-xylosidase (204.7 ± 6.5 U g-1 of perlite) exhibited transxylosylation activity when sugars from black liquor xylan hydrolysate and a variety of alcohols (C1-6) were used as donor and acceptor molecules, respectively, yielding a number of alkyl xylosides. The synthesized hexyl xyloside exhibited some interesting properties comparable with those of a commercial hexyl glucoside, including an antioxidant activity (IC50 = 8.9 ± 2.0 mg mL-1), wetting time (43 s), and critical micelle concentration value (252 mmol L-1). Optimization for hexyl xyloside synthesis was performed via statistical analysis using a Box and Behnken design. The maximum predicted yield of hexyl xyloside (499.0 ± 1.1 mg g-1 xylan hydrolysate) was obtained with 10% (w/v) xylan hydrolysate, 10 U g-1 immobilized β-xylosidase, and 13% (v/v) hexanol at 70 °C, pH 6.0 for 4 h, and it was validated by the following experimental yield (498.9 ± 4.8 mg g-1 xylan hydrolysate). The maximum production yield remained relatively stable after the immobilized enzyme was reused for 12 cycles with a 471.5 ± 15.1 mg g-1 hexyl xyloside yield (94.4% of the first cycle). Thus, the immobilized β-xylosidase has a high potential as a robust catalyst for application in alkyl xyloside production.
- Published
- 2020
4. Antiviral Activity of Phenolic Derivatives in Pyroligneous Acid from Hardwood, Softwood, and Bamboo
- Author
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Ryota Ouda, Ruibo Li, Takashi Watanabe, Shinsuke Marumoto, Mitsuyoshi Yatagai, Seiji P. Yamamoto, Hiroshi Nishimura, Ryo Narita, and Takashi Fujita
- Subjects
Bamboo ,Catechol ,Softwood ,Renewable Energy, Sustainability and the Environment ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Pyroligneous acid ,Viral inhibition ,Hardwood ,Environmental Chemistry ,Organic chemistry ,Phenol ,0210 nano-technology ,Methyl group - Abstract
Pyroligneous acids (PA) from hardwood, softwood, and bamboo significantly disinfected encephalomyocarditis virus (EMCV). Twenty-five kinds of phenolic derivatives in the PAs were identified and quantified. The total amounts of phenolic compounds in bamboo PA is higher than those in the PAs from softwood and hardwood. Phenol, 2-methoxyphenol, 2-methoxy-4-methylphenol, and 2-methoxy-4-ethylphenol are the most abundant compounds in the PAs examined. The activities of all the phenolic compounds against the encephalomyocarditis virus were assessed. The number of phenolic hydroxyl groups significantly affects the antiviral activity, and catechol and its derivatives exhibit higher viral inhibition effects than other phenolic derivatives. In addition, substituents affect the antiviral activity of the compounds. Phenolic compounds with a methyl group show higher activities than with a methoxyl group (e.g., 2-methylphenol > 2-methoxyphenol). Moreover, the relative position of functional groups also plays a key role...
- Published
- 2017
5. Structure-dependent antiviral activity of catechol derivatives in pyroligneous acid against the encephalomycarditis virus
- Author
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Chihiro Kimura, Ryo Narita, Ruibo Li, Hiroshi Nishimura, Takashi Fujita, Takashi Watanabe, Ryota Ouda, and Mitsuyoshi Yatagai
- Subjects
chemistry.chemical_classification ,Reactive oxygen species ,Catechol ,Chemistry ,Stereochemistry ,General Chemical Engineering ,Substituent ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Virus ,0104 chemical sciences ,chemistry.chemical_compound ,Immune system ,Viral life cycle ,Pyroligneous acid ,0210 nano-technology ,IC50 - Abstract
The pyrolysis product, wood vinegar (WV), from Japanese larch exhibited strong antiviral activity against the encephalomycarditis virus (EMCV). Catechol, 3-methyl-, 4-methyl-, 4-ethyl-, and 3-methoxycatechol, and 2-methyl-1,4-benzenediol were identified as the major antiviral compounds. The viral inhibition ability of these compounds was affected by the structure and position of the substituent group attached to the aromatic skeleton. The IC50 of catechol was 0.67 mg mL−1 and those of its derivatives were
- Published
- 2018
6. A Facile Visible-Light-Induced Route to Functionalize Polymeric Substrates by Combining Controlled Radical Grafting Polymerization and Thiol−Yne Click Chemistry with Photoredox Catalyst Ir(ppy)3
- Author
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Lianying Liu, Changwen Zhao, Yuhong Ma, Haochuan Chen, Wantai Yang, and Ruibo Li
- Subjects
Polymers and Plastics ,Chemistry ,Organic Chemistry ,technology, industry, and agriculture ,Condensed Matter Physics ,Methacrylate ,Photochemistry ,Grafting ,chemistry.chemical_compound ,Photopolymer ,Polymerization ,Polymer chemistry ,Propargyl ,Materials Chemistry ,Click chemistry ,Reversible addition−fragmentation chain-transfer polymerization ,Physical and Theoretical Chemistry ,Maleimide - Abstract
A novel strategy, based on surface-initiated grafting polymerization and post-polymerization thiol-yne click chemistry, with Ir(ppy)3 as a sole photoredox catalyst, under visible light irradiation is developed. The “livingness” of the grafting polymerization is demonstrated by the linear increase of the graft yield with irradiation time and the block grafting polymerization. Then, acetenyl groups of poly(propargyl methacrylate) (PPMA) grafting chains are reacted with pentaerythritoltetra-(3-mercaptopropionate) via the thiol-yne click reaction. The successful introduction of reactive thiol groups onto the low-density polyethylene-graft-poly(propargyl methacrylate) (LDPE-g-PPMA) films is demonstrated by Fourier transform IR (FTIR) and X-ray photoelectron spectra (XPS) spectroscopy, and the thiol-ene click reaction with N-(1-pyrenyl) maleimide.
- Published
- 2014
7. Determination of Benzo[a]pyrene-7,10-quinone in Airborne Particulates by Using a Chemiluminescence Reaction of Hydrogen Peroxide and Hydrosulfite
- Author
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Akira Toriba, Jin-Ming Lin, Kazuichi Hayakawa, Ruibo Li, and Takayuki Kameda
- Subjects
Detection limit ,Semiquinone ,Chemistry ,Photochemistry ,Analytical Chemistry ,law.invention ,Quinone ,chemistry.chemical_compound ,Sulfite ,law ,Excited state ,Hydroxyl radical ,Hydrogen peroxide ,Chemiluminescence - Abstract
An ultraweak chemiluminescence (CL) was observed when sodium hydrosulfite (NaHSO(3)) reacts with hydrogen peroxide (H(2)O(2)) and was enhanced 70 times by adding 10 pmol benzo[a]pyrene-7,10-quinone (7,10-BaPQ). The CL reaction is fast, and it reached maximum intensity in 0.1 s, and then decayed to baseline in 3 s. Mechanism of NaHSO(3)-7,10-BaPQ-H(2)O(2) system were investigated by CL spectrum, radical scavengers and electron spin resonance (ESR). Hydroxyl radical ((•)OH), super oxide anion radical ((•)O(2)(-)), and sulfite radical ((•)SO(3)(-)) were generated in the NaHSO(3)-7, 10-BaPQ-H(2)O(2) system. Reduction of 7,10-BaPQ by (•)O(2)(-) radical gave excited semiquinone, which showed strong CL emission when decayed to its ground state. Maximum CL emission wavelength was located at 440 nm, which may belong to the excited semiquinone. This CL system was developed as post column detection of high performance liquid chromatography for the determination of 7,10-BaPQ. Linearity ranged from 50 fmol to 20 pmol (R(2) = 0.9995) with limit of detection of 30 fmol (S/N = 3). The proposed method was used to determine 7,10-BaPQ in airborne particulates. Average atmospheric concentrations of 7,10-BaPQ in Kanazawa in December 2010 and Wajima in October 2007 were 2.0 and 1.6 pg/m(3), respectively.
- Published
- 2012
8. Chemiluminescence behavior of sodium hydrogen carbonate in the potassium permanganate-hydrogen peroxide reaction
- Author
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Guangsheng Guo, Jin-Ming Lin, Chao Lu, RuiBo Li, and Hui Chen
- Subjects
Singlet oxygen ,Sodium ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Ascorbic acid ,law.invention ,chemistry.chemical_compound ,Potassium permanganate ,chemistry ,law ,Rhodamine B ,Sodium azide ,Hydrogen peroxide ,Chemiluminescence - Abstract
Chemiluminescence (CL) phenomenon of hydrogen peroxide with potassium permanganate in the presence of sodium hydrogen carbonate was reported. Effects of the surfactant on the CL system were investigated. Nonionic surfactants could effectively increase the CL signal. Radical scavengers and organic reagents such as nitro blue tetrazolium chloride (NBT), cytochrome c, sodium azide, ascorbic acid, thiourea, tert-butanol and dimethyl sulphoxide were used to study the emitting species. CL emission spectrum was recorded and the results showed that the maximal emission wavelengths of NaHCO3-H2O2-KMnO4 system were 440 and 634 nm. The mechanism was discussed based on electron spin resonance (ESR) spectra, fluorescence spectra and UV-vis absorption spectra. The addition of rhodamine B or uranine into this CL system enhanced the CL signal. It was due to part of the energy transfer from singlet oxygen and excited triplet dimers of two CO2 molecules to rhodamine B or uranine. The CL could be induced by excited rhodamine B or uranine.
- Published
- 2010
9. Substituent effects in addition of iodine thiocyanate to alkenes
- Author
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Ruibo Li, Donna J. Nelson, and Christopher N. Brammer
- Subjects
Steric effects ,chemistry.chemical_classification ,Thiocyanate ,Alkene ,Organic Chemistry ,Substituent ,chemistry.chemical_element ,Iodine ,Branching (polymer chemistry) ,Photochemistry ,Biochemistry ,Medicinal chemistry ,chemistry.chemical_compound ,Degree of substitution ,chemistry ,Drug Discovery ,Alkyl - Abstract
The plots of logarithms of relative rates of ISCN addition to alkenes versus alkene IPs and versus alkene HOMO energies reveal that the alkene relative reactivity depends upon both electronic and steric effects of the substituents. Steric effects are related not only to the degree of substitution on the C C bond but also to the relative position, size, and branching of alkyl substituents.
- Published
- 2007
10. Correlation of relative rates of chromyl chloride oxidation and chromic acid oxidation of acyclic alkenes versus alkene IPs and HOMOs
- Author
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Donna J. Nelson, Christopher N. Brammer, and Ruibo Li
- Subjects
Steric effects ,chemistry.chemical_classification ,Chemistry ,Alkene ,Electrophilic addition ,Organic Chemistry ,Photochemistry ,Cycloaddition ,chemistry.chemical_compound ,Transition metal ,Electrophile ,Chromic acid ,Physical and Theoretical Chemistry ,Chromyl chloride - Abstract
Plots of logarithms of relative reaction rates of chromyl chloride oxidation and of chromic acid oxidation of alkenes (log krel values) versus alkene ionization potentials (IPs) and versus their highest occupied molecular orbital energy levels (HOMOs) demonstrate excellent correlations. Each plot has a similar appearance and shows a single line with a positive slope. The results indicate that the rate-determining step of each title reaction involves an electrophilic attack on the alkene π-bond without significant steric effects; this supports a proposed 2 + 3 cycloaddition mechanism and disfavors a proposed stepwise 2 + 2 cycloaddition mechanism. Comparison is made with other d0 transition metal complexes that oxidize alkenes. Copyright © 2004 John Wiley & Sons, Ltd.
- Published
- 2004
11. Substituent effects in acid-catalyzed hydration of alkenes, measured under consistent reaction conditions
- Author
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Christopher N. Brammer, Ruibo Li, and Donna J. Nelson
- Subjects
Reaction conditions ,chemistry.chemical_classification ,Steric effects ,Chemistry ,Alkene ,Organic Chemistry ,Substituent ,Photochemistry ,Biochemistry ,Reaction rate ,chemistry.chemical_compound ,Computational chemistry ,Acid catalyzed ,Drug Discovery ,Reactivity (chemistry) - Abstract
A set of convenient conditions for the title reaction is used to determine directly relative reactivities of alkenes with widely-varying steric requirements. Previous determinations did not use one set of conditions for all alkenes, but developed parameters in order to compare alkene reaction rates run in different solvents and in different concentrations; such an indirect reactivity comparison can introduce errors. Relative rates established under this common set of reaction conditions are compared to those previously calculated by using correction parameters. Comparison reveals that the approximate method overestimated effects of some groups attached to C C, such as methyl and chloro.
- Published
- 2009
12. Enhancing effect of alcoholic solvent on hydrosulfite-hydrogen peroxide chemiluminescence system
- Author
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Ruibo Li, Chao Lu, Ying Li, Jin-Ming Lin, and Hui Chen
- Subjects
Sodium ,Inorganic chemistry ,chemistry.chemical_element ,Photochemistry ,law.invention ,Solvent ,chemistry.chemical_compound ,chemistry ,Sulfite ,law ,Hydroxyl radical ,Physical and Theoretical Chemistry ,Hydrogen peroxide ,Chemiluminescence - Abstract
In this work, a chemiluminescence (CL) reaction between hydrogen peroxide (H(2)O(2)) and sodium hydrosulfite (NaHSO(3)) was developed. Hydroxyl radical ((•)OH) and sulfite radical ((•)SO(3)(-)) were the main intermediates generated in the NaHSO(3)-H(2)O(2) CL system. Inhibition effects of radical scavengers such as thiourea, chloride ion, nitro blue tetrazolium chloride (NBT), and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) indicated the existence of these two radicals. Singlet oxygen ((1)O(2)) and excited sulfur dioxide (SO(2)*) were emitting species involved in NaHSO(3)-H(2)O(2) CL system. (1)O(2) were confirmed by 1,4-diazobicyclo[2,2,2]octane (DABCO) and sodium azide (NaN(3)), which were specific (1)O(2) scavengers. In addition, electron spin resonance (ESR) spectra clearly show the existence of (1)O(2) and (•)OH. Alcoholic solvent, especially n-butanol, enhanced the ultraweak CL emission more than 40 times. The enhancing effect of alcoholic solvent on NaHSO(3)-H(2)O(2) CL system was ascribed to the formation of solvent cage, which can accelerate the reaction rate and protect the emitting species from quenching by water. The CL emission of the NaHSO(3)-n-butanol-H(2)O(2) system was measured by cutoff filters. The maximum wavelength was located around 490 nm, which belongs to (1)O(2). The wide peak from 400 to 600 nm is the characteristic peak of SO(2)*.
- Published
- 2012
13. Hydrogen peroxide-sodium hydrosulfite chemiluminescence system combined with high-performance liquid chromatography for determination of 1-hydroxypyrene in airborne particulates
- Author
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Ning Tang, Ruibo Li, Jin-Ming Lin, Kazuichi Hayakawa, Akira Toriba, Ying Li, and Takayuki Kameda
- Subjects
Detection limit ,Chromatography ,Sodium ,chemistry.chemical_element ,Particulates ,High-performance liquid chromatography ,Peroxide ,Analytical Chemistry ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Methanol ,Hydrogen peroxide ,Chemiluminescence - Abstract
In this research, a highly sensitive chemiluminescence method based on a sodium hydrosulfite (NaHSO3)–hydrogen peroxide (H2O2) reaction for the determination of 1-hydroxypyrene (1-OHP) was developed. The response of this system was linear in the range from 0.5 to 50 pmol (R2 = 0.9983). The limit of detection for 1-OHP was 100 fmol (S/N = 3). 1-OHP in airborne particulates was well separated from interfering compounds using an ODS column with 75% methanol as the mobile phase in isocratic mode. The proposed method was successfully applied to determine the 1-OHP in airborne particulates collected in Kanazawa, Japan. The average concentration of 1-OHP in the atmosphere was 2.0 pg/m3 (9.2 fmol/m3).
- Published
- 2011
14. Determination of L-ascorbic acid in human serum by chemiluminescence based on hydrogen peroxide-sodium hydrogen carbonate-CdSe/CdS quantum dots system
- Author
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Hui Chen, Jin-Ming Lin, Guangsheng Guo, Ruibo Li, and Ling Lin
- Subjects
Luminescence ,Hydrogen ,Inorganic chemistry ,chemistry.chemical_element ,Ascorbic Acid ,Analytical Chemistry ,law.invention ,chemistry.chemical_compound ,Blood serum ,law ,Limit of Detection ,Quantum Dots ,Spectroscopy, Fourier Transform Infrared ,Cadmium Compounds ,Hydroxides ,Humans ,Hydrogen peroxide ,Selenium Compounds ,Chemiluminescence ,Hydroxyl Radical ,Electron Spin Resonance Spectroscopy ,Reproducibility of Results ,Hydrogen Peroxide ,Hydrogen-Ion Concentration ,Ascorbic acid ,Kinetics ,Sodium Bicarbonate ,chemistry ,Hydroxide ,Hydroxyl radical ,Sodium carbonate - Abstract
In the present work, a strongly chemiluminescence (CL) from the mixing of hydrogen peroxide (H(2)O(2)), hydrogen carbonate (HCO(3)(-)) and CdSe/CdS quantum dots (QDs) was observed. The addition of trace amount of L-ascorbic acid into the CL system caused significant quenching luminescence intensity. Based on this phenomenon, a flow injection CL analysis system for the determination of l-ascorbic acid was developed. The CL reaction conditions, such as mixing orders and concentrations of CL reagents, flow rates, pH, and particle size of quantum dots have been optimized. The CL intensity and the concentration of L-ascorbic acid have a good linear relationship in the ranges of 1.0x10(-7)-1.0x10(-4)molL(-1) (R(2)=0.9916). The limit of detection for L-ascorbic acid is 6.7x10(-9)molL(-1) (S/N=3). This method has been successfully applied to determine L-ascorbic acid in human serum. The recoveries for the real samples were from 83% to 111% and the variance coefficient was
- Published
- 2010
15. Using correlations to compare additions to alkenes: homogeneous hydrogenation by using Wilkinson's catalyst
- Author
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Ruibo Li, Christopher N. Brammer, and Donna J. Nelson
- Subjects
chemistry.chemical_classification ,Addition reaction ,Nucleophilic addition ,Double bond ,Electrophilic addition ,Alkene ,Organic Chemistry ,Photochemistry ,Wilkinson's catalyst ,Catalysis ,chemistry.chemical_compound ,Wacker process ,chemistry ,Physical chemistry - Abstract
Plots of the logarithms of relative rates of homogeneous catalytic hydrogenation of alkenes (log k(rel) values) by using Wilkinson's catalyst versus their ionization potentials (IPs) and versus their lowest unoccupied molecular orbital energy levels (LUMOs) display good-to-excellent correlations. The correlations indicate that the rate-determining step of this reaction is a nucleophilic addition to the alkene double bond, which is dependent upon both electronic effects and steric effects. This conclusion is in agreement with only two of three previously proposed mechanisms for the reaction, effectively ruling out one in which the rate-determining step involves electrophilic addition to the alkene. Characteristics of the analysis using these correlations are compared and contrasted with other additions to alkenes, such as the Wacker oxidation, to probe patterns in transition state characteristics.
- Published
- 2005
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