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140 results on '"Yu Shu-Qin"'

4. Synthesis of Oxazoles Containing CF 3 -Substituted Alcohol Unit via Tandem Cycloisomerization/Hydroxyalkylation from N -Propargylamides with Trifluoropyruvates.

Author

Gao, Juan-Juan, Wu, Long-Hui, Yu, Shu-Qin, Zhu, Xue, Zeng, Yu, Yang, Kai, and Wang, Zhao-Yang

Subjects
OXAZOLES synthesis, DRUG discovery, PHARMACEUTICAL chemistry, CYCLOISOMERIZATION, OXAZOLES
Abstract

Oxazoles are important five-membered heterocycles that contain both nitrogen and oxygen atoms. Due to their wide range of biological activities, many oxazoles demonstrate potential for extensive application in various fields, including medicinal chemistry. Trifluoromethyl carbinol, an important pharmacophore, contains both trifluoromethyl and hydroxyl groups and is common in molecules with important biological activities. Constructing oxazoles that contain a trifluoromethyl carbinol unit is undoubtedly important and valuable for expanding the chemical space in drug discovery. In this study, a simple and efficient method was developed for the synthesis of oxazoles containing a CF3-substituted alcohol unit via the tandem cycloisomerization/hydroxyalkylation of N-propargylamides with trifluoropyruvates through a rational Lewis acid catalytic mechanism. This Zn(OTf)2-catalyzed synthetic protocol is operationally simple and provides a series of oxazoles in moderate to good yields. The protocol demonstrates broad substrate scope, high functional group tolerance, and high atom economy and can achieve gram-level reactions, indicating the strong possibility of its practical application. [ABSTRACT FROM AUTHOR]

Published
2024
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19. Theoretical investigation on the N+SF[sub 2]→NS[sup +] reaction involving resonance-enhanced multiphoton ionization process.

Author

Liu, Ya-Jun, Huang, Ming-Bao, Zhou, Xiao-Guo, Li, Quan-Xin, and Yu, Shu-Qin

Subjects
NITROGEN compounds, IONIZATION (Atomic physics), PHOTOELECTRON spectroscopy
Abstract

NS[SUP+] was detected from ionization of the final product of the N([SUP2]D)+ SF[SUB2] reaction by laser multiphoton ionization. NS is not the spectral carrier of our REMPI (resonance-enhanced multiphoton ionization) spectrum. For understanding the experimental facts and to obtain a complete description of the whole process, quantum-chemical calculations were performed. The density functional theory/Becke's three-parameter hybrid-function calculations indicate that NSF is the product of the most favorable channel of the N+ SF[SUB2] reaction. The complete active space self-consistent field (CASSCF) potential energy curve calculations predict that 1 [SUP1]A″ is a predissociative state of NSF with the NS radical and F atom as the dissociation products. The CASSCF vibrational frequencies calculated at the 1 [SUP1]A″ minimum are in line with the excitation spectrum. The CASPT2 adiabatic excitation energy value of 3.32 eV for the 1 [SUP1]A″ state is close to the energy value (3.44 eV) of one photon. On the basis of theoretical calculations, it is concluded that NS[SUP+] detected in the experiments is produced by one-photon dissociation and ionization of the 1 [SUP1]A″ excited state of NSF, which is the product of the most favorable channel of the N+ SF[SUB2] reaction. [ABSTRACT FROM AUTHOR]

Published
2002
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21. Studies on the Thermal Behavior of Polyurethanes

Author

Yu Shu-Qin, Li Shufen, Wan Ki Chow, Yuan Kaijun, and Jiang Zhi

Subjects
Materials science, Polymers and Plastics, General Chemical Engineering, Materials Science (miscellaneous), Thermal decomposition, Combustion, Decomposition, Thermogravimetry, chemistry.chemical_compound, chemistry, Thermal, Materials Chemistry, Thermal stability, Composite material, Polyurethane, Fire retardant
Abstract

The number of fires appear to be increasing all over the world with some big fires started from burning sofa polyurethane foam (PUF). The general public is quite concerned about the risk of fire due to the extensive use of polyurethane-based materials. Better understanding of the fire behavior of the materials would provide guidelines on fire safety provision. The first step is to review the thermal decomposition mechanisms of polyurethane under different environmental conditions, which will be reported in this paper. Recent studies on the thermal decomposition kinetics and thermal stability of polyurethane are described. Thermal decomposition and combustion reactions of polyether-polyurethane and polyester-polyurethane in air and nitrogen atmospheres investigated by using thermogravimetry analysis will then be outlined. The kinetic processes of polyurethane decomposition studied by the model fitting method are discussed. Polyester-polyurethane was found to be thermally more stable than polyether-polyuret...

Published
2006
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22. Resonance-enhanced multiphoton ionization spectra of the halogen atoms

Author

Jin Jin, Ran Qin, Pei Lin-Sen, Chen Cong-Xiang, Yu Shu-Qin, Ma Xing-Xiao, and Chen Yang

Subjects
symbols.namesake, Time of flight, Resonance-enhanced multiphoton ionization, Materials science, Stark effect, Excited state, Ionization, Halogen, symbols, General Physics and Astronomy, Atomic physics, Quantum number, Spectral line
Abstract

The resonance-enhanced multiphoton ionization (REMPI) spectra of atomic chlorine and bromine in the range of 230-245 nm and 250-285 nm were obtained by using REMPI and time of flight (TOF) techniques. There are twenty-six lines for Cl and twenty-three for Br in the spectra, among which five transitions of Cl and four of Br are observed for the first time. These lines are due to transitions from the Cl(3p 2P3/20, 2P1/20) and Br(4p 2P3/20, 2P1/20) states to upper states induced by two-photon excitation. It is found that the Stark shift of different excited states are almost the same, and they are independent of the S, L, and J quantum numbers of the excited state.

Published
1999
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25. Two photons excited 4d Rydberg state of AsH 3

Author

Ran Qin, Chen Cong-Xiang, Pei Lin-Sen, Wang Fei, Chen Yang, Yu Shu-Qin, and Ma Xing-Xiao

Subjects
Physics, symbols.namesake, Rydberg constant, Ionization, Excited state, Rydberg atom, symbols, General Physics and Astronomy, Rydberg matter, Atomic physics, Rydberg state, Hydrogen spectral series, Resonance (particle physics)
Abstract

In this paper, by using resonance enhanced (2+1) multiphoton ionization (REMPI) of AsH3 and detecting the daughter molecular ions AsH+ and As+, a long progression discrete structure was obtained from 267 to 291 nm, which obeys the formula v0(cm-1)=68875.3+504.1v'2+5.26v'22. Analysis of the spectrum has revealed that it belongs to 4d Rydberg state transition. Our assignment yields the 4d Rydberg state parameters Te'=67881.1 cm-1, we'=495.1 cm-1 and δ=0.962. Finally the 4d Rydberg state structure of AsH3 was discussed.

Published
1998
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31. Electroless Copper Deposition in the Photographic Gelatin Layer

Author

Yu Shu-Qin, Yan Tian-tang, Zhang Yi-heng, and Zhuang Si-yong

Subjects
food.ingredient, Renewable Energy, Sustainability and the Environment, Methionine sulfoxide, Inorganic chemistry, chemistry.chemical_element, Condensed Matter Physics, Copper, Gelatin, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Catalysis, chemistry.chemical_compound, Colloid, food, chemistry, X-ray photoelectron spectroscopy, Chloroauric acid, Materials Chemistry, Electrochemistry, Layer (electronics), Nuclear chemistry
Abstract

An electroless copper deposition process consisting of two stages: (1) forming gold catalytic centers, and (2) electroless copper deposition, was studied in this paper. The changes of the chemical state of sulfur in photographic gelatin before and after electroless copper deposition were studied by X-ray photoelectron spectrometry. The depth distribution of copper and gold within the electrically conductive layer produced by electroless copper deposition was determined and the mechanism of electroless copper deposition catalyzed by gold in the photographic gelatin layer was discussed. The results indicated that under acidic conditions (pH 3.20), methionine sulfoxide in the gelatin macromolecule had relatively high reducing power. When the gelatin sample was immersed into the chloroauric acid solution, methionine sulfoxide and methionine were oxidized to methionine sulfone, reducing Au 3+ to colloid gold which acted as the catalytic center at the initial stage of the electroless copper deposition. During the electroless deposition, the reduction of Cu 2+ by HCHO could continue, and even the copper completely covered the gold because the reaction was autocatalyzed by newly formed copper.

Published
1999
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