检索结果-南通市图书馆

Chinese Chemical Letters 2018年第8期29卷 1264-1268页

作者： Siwei Bi Peng Liu Baoping Ling Xiangai Yuan Yuanye Jiang School of Chemistry and Chemical Engineering Qufu Normal University

N-（2-Hydroxybenzyl）cysteine derivatives were recently disclosed to be efficient crypto-thioesters for native chemical ligation（NCL）. To elucidate the mechanism of the relevant N-to-S acyl transfer process as well as the origin of the acceleration effect of the phenol substitutes, a density functional theory（DFT）study was performed. It was found that the N-to-S acyl transfer of N-（2-hydroxybenzyl）cysteine derivatives involve four major steps： concerted nucleophilic addition of thiolate/proton transfer,inversion of an amine moiety, water-assisted proton transfer and CààN bond cleavage. The phenol substitutes promote the nucleophilic addition of thiolate by protonating the carbonyl oxygen atom synergistically and the proton transfer from hydroxyl to amide nitrogen atom is the rate-determining step of the N-to-S acyl transfer. By contrast, changing the phenolic hydroxyl to methoxyl was found to significantly slow down the nucleophilic addition of thiolate and thus hinders the N-to-S acyl transfer overall. These computational results are consistent with the observation of previously reported control experiments, by which our proposed mechanism is further validated.

关键词： Native chemical ligation Acyl transfer Density functional theory Phenol Proton transfer

High‑Entropy Layered Oxide Cathode Enabling High‑Rate for Solid‑State Sodium‑Ion Batteries

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2024年第1期16卷 160-171页

作者： Tianxun Cai Mingzhi Cai Jinxiao Mu siwei Zhao Hui bi Wei Zhao Wujie Dong Fuqiang Huang State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050People’s Republic of China State Key Laboratory of Rare Earth Materials Chemistry and Applications College of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871People’s Republic of China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049People’s Republic of China Zhongke Institute of Strategic Emerging Materials Yixing 214213JiangsuPeople’s Republic of China

Na-ion O3-type layered oxides are prospective cathodes for Na-ion batteries due to high energy density and low-cost.Nevertheless,such cathodes usually suffer from phase transitions,sluggish kinetics and air instability,making it difficult to achieve high performance solid-state sodium-ion batteries.Herein,the high-entropy design and Li doping strategy alleviate lattice stress and enhance ionic conductivity,achieving high-rate performance,air stability and electrochemically thermal stability for Na_(0.95)Li_(0.06)Ni_(0.25)Cu_(0.05)Fe_(0.15)Mn_(0.49)O_(2).This cathode delivers a high reversible capacity(141 mAh g^(−1)at 0.2C),excellent rate capability(111 mAh g^(−1)at 8C,85 mAh g^(−1)even at 20C),and long-term stability(over 85%capacity retention after 1000 cycles),which is attributed to a rapid and reversible O3–P3 phase transition in regions of low voltage and suppresses phase transition.Moreover,the compound remains unchanged over seven days and keeps thermal stability until 279℃.Remarkably,the polymer solid-state sodium battery assembled by this cathode provides a capacity of 92 mAh g^(−1)at 5C and keeps retention of 96%after 400 cycles.This strategy inspires more rational designs and could be applied to a series of O3 cathodes to improve the performance of solid-state Na-ion batteries.

关键词： High-entropy High-rate performance Li-TM interaction Air stability O3 layered oxide cathode

Theoretical Insight into C(sp3)-F Bond Activation and Origin of Regio-and Chemoselectivities in Nickel-Mediated Couplings of 2-Trifluoromethyl-1-alkenes with Alkynes

在线全文

学校读者我要写书评

暂无评论

Theoretical Insight into C(sp3)-F Bond Activation and Origin...

第十三届全国量子化学会议

作者： Xiaomin Zhang Yuxia Liu Siwei Bi School of Chemistry and Chemical Engineering Qufu Normal University

Organic fluorine compounds such as freon, fluoro-liquid crystals, optical fiber,poly(tetrafluroethylene)(PTFE), pharmaceuticals and agrochemicals etc., have received great interest and attention in diverse fields of science due to their own unique properties that are difficultly obtained from other organic compounds[1 ]. Compared with transition-metal-mediated C-F bond activation of aryl and vinyl fluorides[2 ], the C-F bond activation of the trifluoromethyl group remains a great challenge, which might not only be attributed to the high chemical stability of the C(sp)-F bond but also because of the strong shielding effect of the lone-pair electrons on three F atoms[ 3 ]. Recently, Ichikawa and co-workers developed the Ni(cod)/PCy-mediated selective coupling reactions of 2-trifluoromethyl-1-alkenes and 4-octyne in toluene, which were demonstrated to be available under relatively mild conditions. On the basis of the calculated results, we uncovered(i) the origin of selectively cleaving two C(sp)-F bonds of the trifluoromethyl group in the stoichiometric reaction,(ii)the intrinsic reasons for the EtSiH-dominated chemoselectivity,and(iii) the respective roles of ZnMe and AlMe in dominating the product-divergence. The present theoretical results not only rationalize the experimental observations but provide insight into the mechanism details of the significant Ni-mediated coupling reactions.

关键词： nickel C（sp3）-F activation DFT regioselectivity chemo-selectivity 2-trifluoromethyl-1-alkenes alkynes

Advances in theoretical study on transition-metal-catalyzed C-H activation

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science China Chemistry 2016年第11期59卷 1448-1466页

作者： Yuan-Ye Jiang Xiaoping Man Siwei Bi School of Chemistry and Chemical Engineering Qufu Normal University

Transition-metal-catalyzed C–H activation represents one of most attractive research fields in modern organic chemistry while theoretical studies have become a popular and effective tool for elucidating mechanism nowadays. The recent achievements in the cross field of the two orientations are reviewed in this article. The first part introduced the advances in theoretical study on transition-metal-catalyzed C–H activation. The elegant work reported mainly in and after 2013, classified according to the mechanisms of C–H activation, were covered. The second part provided an analysis on the distribution of quantum-chemical methods, solvation models and basis sets in the collected theoretical studies.

关键词： transition metal C–H activation mechanism DFT

Insight into the Regioselectivity on Cu-Catalyzed Silacarboxylation of Internal Alkynes: a DFT Study

在线全文

学校读者我要写书评

暂无评论

Insight into the Regioselectivity on Cu-Catalyzed Silacarbox...

中国化学会第十二届全国量子化学会议

作者： Yi Zhao Siwei Bi Yongjun Liu School of Chemical Engineering Shandong University of Technology Northwest Institute of Plateau biology Chinese Academy of Sciences School of Chemistry and Chemical Engineering Qufu Normal University

Tsuji and co-workers first reported the Cu-catalyzed silacarboxylation of internal alkynes utilizing CO2 and silylborane affording two isomeric silalactone products P1 and P2 with high regioselectivity[1].In order to get an insight into the origin of the high regioselectivity observed,detailed reaction mechanism was investigated with the help of the density functional theory calculations.[2-4].PCy3Cu-Si Me2Ph is believed to be the active catalyst.Syn addition of the internal alkyne R to the active catalyst was the selectivity-determining step and the rate-determining step.The electronic aspect is found in favor of the formation of P1 rather than P2.

关键词：

High-resolution angle-Doppler imaging by sparse recovery of underwater acoustic signals

在线全文

cnki会议

学校读者我要写书评

暂无评论

Chinese Journal of Acoustics 2020年第2期39卷 133-150页

作者： KOU siwei FENG Xi’an bi Yang HUANG Hui School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072

The low resolution of Fourier two-dimensional spatial temporal spectrum estimation and the insufficient sample size of sonar space time sampling data often caused difficulties in high-resolution space time spectrum estimation. Aiming to solve this problem, we proposed a high-resolution angle-Doppler imaging method and designed an anti-reverberation space time filter based on the sparse recovery of underwater acoustic signals. The proposed imaging method established the spatial temporal sparse representation model of array signal under the condition of few observation samples of single measurement vector(SMV), and reconstructed the high-resolution angle-Doppler profile of echo and reverberation through the matching pursuit(MP) algorithm and basis pursuit(BP) algorithm. By utilizing the space time distribution characteristics of echo and reverberation and the prior information of sonar rangecell under test(RUT), a reverberation dictionary composed of special space time guidance vectors was designed, and was used to reconstruct the reverberation and formed an anti-reverberation space time filter to suppress the reverberation interference of angle-Doppler plane. Computer simulations indicated that, under two conditions of forward and side-view array of moving sonar, the single measurement vector of sonar array was successfully used in the reverberation background to reconstruct the high-resolution angle-Doppler profile of low-speed moving target multi-spot echo. Its frequency resolution had a better performance than the Fourier resolution and the angle resolution broke through the Rayleigh limit of the array, the resolution was obviously superior to the Fourier space time spectrum estimation.

关键词： resolution angle underwater

The Role of Tertiary Butyl Anion and Water in the Water-Assisted Pd（OAc）2-Catalyzed C-C bond Formation: A DFT Study

在线全文

学校读者我要写书评

暂无评论

The Role of Tertiary Butyl Anion and Water in the Water-Assi...

中国化学会第十二届全国量子化学会议

作者： bingwen Li Yuxia Liu Siwei Bi School of Chemistry and Chemical Engineering Qufu Normal University

The tertiary butyl anion in the reaction plays a crucial role for C=C bond formation.Make clear why the additionally added water can accelerate the reaction.In addition,the carbonyl unit in the alkene is confirmed to ...

关键词：

C-H Activation versus Ring Opening and Inner-versus Outer-Sphere Concerted Metalation-Deprotonation in Rh（Ⅲ）-Catalyzed Oxidative Coupling of Oxime Ether and Cyclopropanol: A Density Functional Theory Study

在线全文

cnki会议

学校读者我要写书评

暂无评论

C-H Activation versus Ring Opening and Inner-versus Outer-Sp...

中国化学会第十六届全国均相催化学术会议

作者：孟冉 Siwei Bi Yuan-Ye Jiang Yuxia Liu 曲阜师范大学 School of Chemistry and Chemical Engineering Qufu Normal University

＜正＞The Rh（Ⅲ）-catalyzed oxidative coupling of oxime ether （S1） and cyclopropanol （S2） with Cu（Ⅱ） as the oxidant features the combination of C-H activation and strained ring opening. The sequential order of C-H activation versus ring opening was investigated with the aid of density functional theory calculations. Prior ring opening due to the release of ring strain is found to be favored over the prior C-H activation. For the prior ring-opening mechanisms, the outer-sphere concerted metalation-deprotonation （CMD） mechanism in C-H bond activation is energetically favored.

关键词： outer-sphere ring opening oxidative coupling DFT

Understanding the Reactions of Aryl Iodides with Alkynes to Give New C-C and C-I bonds: A DFT Study

在线全文

cnki会议

学校读者我要写书评

暂无评论

Understanding the Reactions of Aryl Iodides with Alkynes to ...

中国化学会第十二届全国量子化学会议

作者： Yanan Tang Hongliang Wang Yuxia Liu Siwei Bi School of Chemistry and Chemical Engineering Qufu Normal University

The reactions of 2-iodo- -methyl styrene with symmetric and asymetric acetylenes have been theoretically studied with the aid of density functional theory calculations.It is found that for formations of P1 to P3 similar reaction mechanisms are involved,but for formation of P4containing a three-C ring unit the reaction mechanism is unique.Actually,the steric effect caused by the phosphine ligands is found to be important for forming the products.

关键词：

Unraveling the Formation Mechanism of Subphthalocyanine.Density Functional Theory Studies

在线全文

cnki会议

学校读者我要写书评

暂无评论

Unraveling the Formation Mechanism of Subphthalocyanine.Dens...

中国化学会第四届卟啉与酞菁学术研讨会

作者： Chiming Wang Xin Chen Dongdong Qi Siwei Bi Jianzhuang Jiang Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials Department of ChemistryUniversity of Science and Technology Beijing School of Chemistry and Chemical Engineering Qufu Normal University

A systematic investigation over the formation mechanism of the subphthalocyanine,SubPc（Cl）,with phthalonitrile as the initial reagent mediated by boron trichloride in the solvent of p-xylene has been carried out on the basis of density functional theory,revealing truly a long reaction pathway containing twenty-three elementary reactions.The calculation results well reproduce and rationalize the experimental findings including the selection of high boiling point reaction media of p-xylene,employment of excessive amount of BCl3 reagent,and liberation of Cl2 during the reaction process.In particular,the crucial catalytic nature of BCl3 has been clearly disclosed:In addition to activating the cyano groups,boron trichloride also works as chloride-transfer shuttle to prompt the reactions occurring and proceeding.The present result will put forwards the exploration over the formation mechanisms of phthalocyanines and porphyrins.

关键词： Subphthalocyanine DFT Reaction mechanism