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117 results on '"Cai, Pei‐Jun"'

12. Crystal structure of 2-amino-5,6,7,8-tetrahydro-4,7,7-trimethyl-4-(4- nitrophenyl)-5-oxo-4H-chromene-3-carbonitrile DMF solvate, C19H19N3O5·DMF, C22H26N4O5

Author

Cai Pei-Jun, Guo Xiao-Feng, Huo Jun-Hao, and Shi Chong

Subjects
Physics, QC1-999, Crystallography, QD901-999
Abstract

C22H26N4O5, triclinic, P1̄ (no. 2), a = 8.4753(6) Å, b = 9.5662(7) Å, c = 14.479(1) Å, α = 101.674(4)°, β = 93.813(4)°, γ= 104.676(4)°, V = 1103.5 Å3, Z = 2, Rgt(F) = 0.0581, wRref(F2) = 0.1863, T = 296 K.

Published
2012
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15. Silver‐Catalyzed Nitration/Annulation of α‐Alkynyl Arylols toward 3‐Nitrated Benzofurans.

Author

Zhang, Tian‐Shu, Yang, Lei, Cai, Pei‐Jun, Tu, Shu‐Jiang, and Jiang, Bo

Subjects
BENZOFURAN synthesis, BENZOFURANS, ANNULATION, NITRATION, ALKYNES, PROCEEDS, NITRITES
Abstract

A silver‐catalyzed nitration/annulation of α‐alkynyl arylols is reported by using tert‐butyl nitrite (TBN) as a NO2 radical precursor, from which a set of 3‐nitrated benzofurans were synthesized with moderate to good yields. This transformation initiated by an in situ generated NO2 radical proceeds efficiently under mild and neutral redox conditions, which provides a new pathway toward the 3‐nitrobenzofuran framework via catalytic difunctionalization of internal alkynes. [ABSTRACT FROM AUTHOR]

Published
2019
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24. Understanding Regioselectivities of Corey–Chaykovsky Reactions of Dimethylsulfoxonium Methylide (DMSOM) and Dimethylsulfonium Methylide (DMSM) toward Enones: A DFT Study.

Author

Xiang, Yu, Fan, Xing, Cai, Pei‐Jun, and Yu, Zhi‐Xiang

Subjects
METHYLIDENES, ALDEHYDES, KETONES, CYCLOPROPANATION, EPOXY compounds
Abstract

The Corey–Chaykovsky reaction, using either in situ generated dimethylsulfoxonium methylide (DMSOM) or dimethylsulfonium methylide (DMSM) to react with ketones or aldehydes, is widely used in the synthesis of epoxides. However, when DMSOM and DMSM react with enones (such as chalcone), the former reactions give cyclopropanation products whereas the latter reactions still generate epoxides. DFT calculations have been carried out to understand these different regioselectivities. We found that the cyclopropanation pathways for both DMSOM and DMSM toward chalcone (a model for enones) start with rate‐determining and irreversible 1,4‐addition reactions, followed by easier intramolecular substitution reactions to give cyclopropanes. The overall activation free energies for cyclopropanation are 17.5 and 15.5 kcal/mol for DMSOM and DMSM, respectively. The epoxidation pathways for both DMSOM and DMSM have reversible 1,2‐addition reactions, followed by rate‐determining intramolecular substitution reactions to give epoxides. The computed barriers for the epoxidation are 23.0 and 13.3 kcal/mol for DMSOM and DMSM, respectively. Therefore, the cyclopropanation pathway is favored for DMSOM while epoxidation is preferred for DMSM. We attribute these different reaction scenarios to thermodynamic reasons that DMSOM is more stable than DMSM. The reaction pathways for reactions of other derivatives of DMSM toward enones have also been discussed. The Corey–Chaykovsky Reaction of either in situ generated dimethylsulfoxonium methylide (DMSOM) or dimethylsulfonium methylide (DMSM) with ketones or aldehydes is widely used to synthesize epoxides. However, when DMSOM and DMSM react with enones, the former reactions give cyclopropanes whereas the latter generate epoxides. DFT calculations have been applied to explain the different regioselectivities. [ABSTRACT FROM AUTHOR]

Published
2019
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31. Conformational Bias by a Removable Silyl Group: Construction of Bicyclo[<italic>n</italic>.3.1]alkenes by Ring Closing Metathesis.

Author

Lin, Minggui, Cai, Pei‐Jun, Zeng, Zhixiong, Lin, Na, Shen, Yang, Tang, Bin, Li, Fan, Chen, Chen, Yu, Zhi‐Xiang, and Zhang, Yandong

Subjects
*SILYL group, *ALKENES, *METATHESIS reactions, *DOUBLE bonds, *DENSITY functional theory
Abstract

Abstract: Herein, we report a novel strategy based on a conformationally controlled RCM by a removable silyl group, which allows the facile synthesis of various bicyclo[n.3.1]alkenes, especially a set of highly strained bicyclo[5.3.1]alkenes. Further derivatizations of the silyl group and the resultant double bond of bicyclo[5.3.1]undecene 2 f enabled a concise synthesis of A‐B‐C ring skeleton of taxol. Density functional theory (DFT) calculations suggest that the introduction of a bulky silyl group at C‐5 position of the 1,3‐dialkenylcyclohexanol substrates dramatically lowers the energy bias gap between diaxial conformers (to RCM) and diequatorial conformers (to cross metathesis), thereby favoring the expected RCM reaction to give the challenging bridged molecules. [ABSTRACT FROM AUTHOR]

Published
2018
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32. A low temperature synthetic route to nanocrystalline TiN

Author

Cai, Pei-jun, Li, Gong-zhen, Shi, Chong, Huo, Jun-hao, and Liu, Li-hua

Subjects
synthesis, Nanocrystalline, titanium nitride
Abstract

A simple chemical synthetic route has been developed to prepare nanocrystalline titanium nitride (TiN) in an autoclave, by the reaction of metallic Ti with NaNH2 at low temperature of 500-600 °C. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, and X-ray photoelectron spectra. The possible reaction mechanism of this process is also discussed. This method may be extended to the synthesis of other metal nitrides.

Published
2011

43. Gold(I)-Catalyzed Polycyclization of Linear Dienediynesto Seven-Membered Ring-Containing Polycycles via Tandem Cyclopropanation/CopeRearrangement/C–H Activation.

Author

Cai, Pei-Jun, Wang, Yi, Liu, Cheng-Hang, and Yu, Zhi-Xiang

Subjects
*GOLD catalysts, *RING formation (Chemistry), *POLYCYCLIC compounds, *CARBON-hydrogen bonds, *ACTIVATION (Chemistry), *CYCLOPROPANATION
Abstract

A novelgold(I)-catalyzed polycyclization of easily prepared lineardienediynes has been developed for the construction of fused 5,7,6-tricyclicring systems in one step with high diastereocontrol. The polycyclization,a formal [4 3]/C–H activation reaction, takes place throughgold(I)-catalyzed intramolecular cyclopropanation of diene with diyne,Cope rearrangement of cis-alkenylalkynylcyclopropane,aliphatic C–H activation via a seven-membered-ring allene intermediate,and [1,2]-H and -G (H or OAc) shifts. [ABSTRACT FROM AUTHOR]

Published
2014
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