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37篇 您的检索式:作者名="Zitong Liu"
    题名 作者 年代 出处 被引量
1Enhanced Expression of miR-425 Promotes Esophageal Squamous Cell Carcinoma Tumorigenesis by Targeting SMAD2显示文摘Esophageal squamous cell carcinoma(ESCC) is one of the most common and deadly cancers in the world. Currently, clinical therapy of ESCC remains limited and the five-year survival rate is poor. The function of miR-425 has been reported in multiple human cancers.However, the tumorigenic role and clinical significance of miR-425 in ESCC remains unclear. We found that enhanced expression of miR-425 in ESCC cell lines not only promoted cell proliferation and colony formation, but also increased cellular metastasis. Furthermore, we revealed the mechanism that miR-425 inhibited the expression of SMAD2 by targeting the second binding site in the 30-untranslated region(30-UTR) in ESCC. This mode of action influenced not only SMAD2 mRNA expression but also protein expression. In addition, we detected the expression of miR-425 in ESCC tissues and plasma. Moreover, we analyzed the relationship between miR-425 expression and SMAD2 m RNA expression. We found that miR-425 was overexpressed in ESCC tissues and the plasma relative to adjacent normal tissues and plasma of healthy individuals. Furthermore, there was a negative correlation between miR-425 expression and SMAD2. Taken together, our results show that miR-425 functions as an oncogene by targeting the 30-UTR of SMAD2 and indicate the potential utility of plasma miR-425 as a novel biomarker for ESCC diagnosis.Lingyan Liu Zitong Zhao Wei Zhou Xinyi Fan Qimin Zhan Yongmei Song 2015Journal of Genetics and Genomics2015,42,11:10
2TRAP1 Shows Clinical Significance and Promotes Cellular Migration and Invasion through STAT3/MMP2 Pathway in Human Esophageal Squamous Cell Cancer显示文摘Tumor necrosis factor receptor-associated protein 1(TRAP1), an important member of mitochondrial heat shock protein 90 family, is involved in multiple biological processes in several types of tumors. However, its pathological role in esophageal squamous cell cancer(ESCC) remains unknown. Herein, we demonstrated the clinical value of TRAP1, and its role in apoptosis and motility in ESCC. The clinical potential of TRAP1 was investigated through immunohistochemical analysis in 328 ESCC samples, which revealed that strong TRAP1 expression was associated with increased risk of lymph node metastasis, while high TRAP1 expression correlated with poor prognosis. Expression of TRAP1 was found to be an independent prognostic factor for patients with ESCC. Additionally, the upregulation of TRAP1 antagonized cisplatin-induced apoptosis while its downregulation sensitized cells to cisplatin-induced apoptosis. As revealed by the transwell assay, TRAP1 overexpression promoted cellular migration and invasion as compared to the control groups. In contrast,silencing of endogenous TRAP1 expression attenuated the ability of migration and invasion. Finally, the molecular mechanism investigated in the present study demonstrated that TRAP1-mediated migration and invasion occurred through STAT3/MMP2 signaling pathway. In conclusion, TRAP1 may be considered as a molecular predictive marker for prognosis and a novel molecular candidate for therapeutic target in ESCC.Yunwei Ou Lingyan Liu Liyan Xue Wei Zhou Zitong Zhao Bainan Xu Yongmei Song Qimin Zhan 2014Journal of Genetics and Genomics2014,41,10:8
3Selenophene-Flanked Diketopyrrolopyrrole Based Conjugated Polymers for Ambipolar Field-Effect Transistors显示文摘Summary of main observation and conclusion The development of selenophene-flanked DPP(SeDPP)based copolymers,especially for the ambipolar ones,lags behind other aromatic group flanked DPP-based polymers.Herein,we report two new ambipolar SeDPP-based conjugated polymers.One is the alternating polymer PSeDPPFT with normal SeDPP and 3,4-difluorothiophene units.The other is PSeFDFT,in which the electron acceptor unit is replaced by a new SeDPP derivative,referred as to half-fused SeDPP.The more planar structure of half fused SeDPP endows the backbone of PSeFDFT with good rigidity and planarity.Both polymers exhibit ambipolar transporting properties in air.The PSeFDFT based fleld-effect transistors(FETs)display higher and more balanced ambipolar properties with μnave of 0.27 cm2·V-1·s-1,μe ave of 0.18 cm2·V-1·s-1,and μh ave/μeave of 1.5 than those of PSeDPPFT(μhave=0.11cm2·V-1·s-1,μeave=0.042cm2·V-1·s-1,and μh/μe=2.6).This is attributed to the more planar structure,lower LUMO level,higher HOMO level,and better interchain packing orientations of PSeFDFT by comparing with PSeDPPFT.Therefore,a new molecular design strategy to modulate the hole and electron transporting properties is proposed for conjugated D-A polymers.Dandan Shi Xiaobo Yu Liangliang Chen Daoliang Chen Zitong Liu Xisha Zhang Guanxin Zhang Deqing Zhang 2020Chinese Journal of Chemistry2020,38,10:4
4Frequency-Hopping Frequency Reconnaissance and Prediction for Non-cooperative Communication Network显示文摘The continuous change of communica-tion frequency brings difficulties to the reconnaissance and prediction of non-cooperative communication net-works.Since the frequency-hopping(FH)sequence is usually generated by a certain model with certain regularity,the FH frequency is thus predictable.In this paper,we investigate the FH frequency reconnais-sance and prediction of a non-cooperative communi-cation network by effective FH signal detection,time-frequency(TF)analysis,wavelet detection and fre-quency estimation.With the intercepted massive FH signal data,long short-term memory(LSTM)neural network model is constructed for FH frequency pre-diction.Simulation results show that our parameter es-timation methods could estimate frequency accurately in the presence of certain noise.Moreover,the LSTM-based scheme can effectively predict FH frequency and frequency interval.Gao Li Wei Wang Guoru Ding Qihui Wu Zitong Liu 2021China Communications2021,18,12:4
5Gap-free genome assembly and comparative analysis reveal the evolution and anthocyanin accumulation mechanism of Rhodomyrtus tomentosa显示文摘Rhodomyrtus tomentosa is an important f leshy-fruited tree and a well-known medicinal plant of the Myrtaceae family that is widely cultivated in tropical and subtropical areas of the world.However,studies on the evolution and genomic breeding of R.tomentosa were hindered by the lack of a reference genome.Here,we presented a chromosome-level gap-free T2T genome assembly of R.tomentosa using PacBio and ONT long read sequencing.We assembled the genome with size of 470.35 Mb and contig N50 of∼43.80 Mb with 11 pseudochromosomes.A total of 33382 genes and 239.31 Mb of repetitive sequences were annotated in this genome.Phylogenetic analysis elucidated the independent evolution of R.tomentosa starting from 14.37MYA and shared a recent WGD event with other Myrtaceae species.We identified four major compounds of anthocyanins and their synthetic pathways in R.tomentosa.Comparative genomic and gene expression analysis suggested the coloring and high anthocyanin accumulation in R.tomentosa tends to be determined by the activation of anthocyanin synthesis pathway.The positive selection and up-regulation of MYB transcription factors were the implicit factors in this process.The copy number increase of downstream anthocyanin transport-related OMT and GST gene were also detected in R.tomentosa.Expression analysis and pathway identification enriched the importance of starch degradation,response to stimuli,effect of hormones,and cell wall metabolism during the f leshy fruit development in Myrtaceae.Our genome assembly provided a foundation for investigating the origins and differentiation of Myrtaceae species and accelerated the genetic improvement of R.tomentosa.angping Li Shiqiang Xu Zitong Xiao Jingming Wang Yu Mei Haifei Hu Jingyu Li Jieying Liu Zhuangwei Hou Junliang Zhao Shaohai Yang Jihua Wang 2023Horticulture Research2023,10,3:3
6Paleosol evolution and environmental change in the Huang-Huai-Hai Plain, China显示文摘Paleosols in the Huang-Huai-Hai Plain occur mainly in the Huaibei, Xuhuai, Yischuheand Jiaolai areas. They result from 3 sedimentation-soil formation cycles since the LatePleistocene. Each cycle left calcareous concretions, a dark soil horizon, and a topsoil horizonand/or a stratified soil horizon all derived from loess. This paper examines the composition of theconcretions, compares this with that of the enclosing soil horizons, and draws some environmentalconclusions. Three types occur: embryonic calcareous concretions, mature calcareous concretions,and calcareous hardpans (petrocalcic horizons). The embryonic concretions formed during themid-Holocene (6780±130 yr. B.P.), mature calcareous concretions during the late-Pleistocene(weighted average of 31 samples = 15670±370 yr. B.P.), and calcareous hardpans (petrocalcichorizons) from 16 to 40 ka B.P. The calcium carbonate content increases from 412 g/kg in theembryonic concretions, to 551 g/kg in the mature concretions, and to 691 g/kg in the hardpan,whereas contents of SiO2, Al2O3 and TiO2 decrease accordingly. Spore pollen analysis shows thatthe late-Pleistocene there was dry and cool, whereas the mid-Holocene was warm and humid andlakes were more extensive than today.LIU Liangwu GONG Zitong Institute of Soil Science. Academia Sinica P. O. Box 821. Nanjing 210008, P. R China 1999Chinese Science Bulletin1999,44,S1:2
7Synthesis and cytotoxic activity of genistein derivatives显示文摘Xing Zheng Xu Yao Yunmei Liu Zitong Zheng Jianguo Cao Duanfang Liao 2010Medicinal Chemistry Research2010,,9:1
8Optimal Power Flow Calculation of Active Distribution Network Based on Improved Comprehensive Technology显示文摘Comprehensive unified power flow controller(UPFC)technology can calculate voltage control parameters of UPFC,but it increases the nonlinearity of Newton power flow calculation.When the comprehensive technology is combined with the intelligent algorithm,the control parameters can only be optimized through the active and reactive power of UPFC on the branch,which makes the optimization convergence worse.Therefore,an optimal power flow calculation method for active distribution network based on improved comprehensive technology is proposed.First,based on the analysis of the influence of UPFC on branch power flow,an improved UPFC model is proposed.The accuracy of UPFC control parameters is enhanced by adjusting the voltage phase angle and regulation radius of series side transformer.Second,the optimal control model considering UPFC is established.Finally,the corresponding self-admittance and mutual admittance elements are extracted from the constructed UPFC model and introduced into the Jacobian matrix,so that while the comprehensive technology maintains the dimension of the Jacobian matrix,the intelligent algorithm can directly optimize the control parameters to reduce the search space.The IEEE33 bus system is used for example simulation,the results before and after the improvement are compared,and the Monte Carlo method is used to calculate the two algorithms 50 times respectively based on the installation number of UPFC,which verifies that the proposed optimization method has better convergence and operation speed.CAO Hongji LIU Daobing LI Shichun JIN Zitong YUAN Ye XU Songlin 2022Wuhan University Journal of Natural Sciences2022,27,2:1
9Soils in Islands of South China Sea and their ages显示文摘GONG Zitong LIU Liangwu ZHOU Ruirong 1995Sciantia Geologica Sinica1995,,:1
10Optimal location query based on k nearest neighbours显示文摘Optimal location query in road networks is a basic operation in the location intelligence applications.Given a set of clients and servers on a road network,the purpose of optimal location query is to obtain a location for a new server,so that a certain objective function calculated based on the locations of clients and servers is optimal.Existing works assume no labels for servers and that a client only visits the nearest server.These assumptions are not realistic and it renders the existing work not useful in many cases.In this paper,we relax these assumptions and consider the k nearest neighbours(KNN)of clients.We introduce the problem of KNN-based optimal location query(KOLQ)which considers the k nearest servers of clients and labeled servers.We also introduce a variant problem called relocation KOLQ(RKOLQ)which aims at relocating an existing server to an optimal location.Two main analysis algorithms are proposed for these problems.Extensive experiments on the real road networks illustrate the efficiency of our proposed solutions.Yubao LIU Zitong CHEN Ada Wai-Chee FU Raymond Chi-Wing WONG Genan DAI 2021Frontiers of Computer Science2021,15,2:0
11Residents’ Preferences for Rural Housing Disaster Insurance Attributes in Central and Western Tibet显示文摘Understanding the heterogeneous preferences of individuals for disaster insurance attributes is critical for product improvement and policy design.In an era of global environmental change,the Qinghai-Tibet Plateau is a hotspot of natural hazards.Improving the capability of rural housing disaster insurance to foster local residents’disaster resilience is of great signifcance but remains under addressed.We used a discrete choice experiment approach to provide the frst estimates of rural residents’preferences for rural housing disaster insurance attributes in central and western Tibet.We estimated residents’preferences and willingness-to-pay for the sum insured,subsidy rate,insured object,and perils covered.The potential impacts of increasing the sum insured,expanding the insured object,and lowering subsidy rates were evaluated.Our results suggest that residents prefer products with a high sum insured,high subsidy rate,and a complete list of insured objects.Residents who have experienced specifc hazards tend to prefer the corresponding perils covered.Females and residents who have a closer social network are more likely to purchase insurance.Product improvement and policy simulation results suggest that,while lowering the subsidy rate,increasing the sum insured and expanding the insured object could promote participation and improve residents’welfare.Our results could improve the understanding of the preferences of households in remote regions and support policy implementations.Tingting Yang Zitong Li Yuan Bai Xinli Liu Tao Ye 2023International Journal of Disaster Risk Science2023,14,4:0
12On-tissue chemical derivatization enables spatiotemporal heterogeneity visualization of oxylipins in esophageal cancer xenograft via ambient mass spectrometry imaging显示文摘On-tissue chemical derivatization(OTCD)effectively enhances ionization efficiency of low abundant and poorly ionized functional molecules to improve detection sensitivity and coverage of mass spectrometry imaging(MSI).Combination OTCD and MSI provides a novel strategy for visualizing previously undisclosed metabolic heterogeneity in tumor.Herein,we present a method to visualize heterogeneous metabolism of oxylipins within tumor by coupling OTCD with airflow-assisted desorption electrospray ionization(AFADESI)-MSI.Taking Girard’s P as a derivatization reagent,easily ionized hydrazide and quaternary amine groups were introduced into the structure of carbonyl metabolites via condensation reaction.Oxylipins,including 127 fatty aldehydes(FALs)and 71 oxo fatty acids(FAs),were detected and imaged in esophageal cancer xenograft with AFADESI-MSI after OTCD.Then t-distributed stochastic neighbor embedding and random forest were exploited to precisely locate the distribution of oxylipins in heterogeneous tumor tissue.With this method,we surprisingly found almost all FALs and oxo FAs significantly accumulated in the core region of tumor,and exhibited a gradual increase trend in tumor over time.These results reveal spatiotemporal heterogeneity of oxylipins in tumor progression,highlighting the value of OTCD combined with MSI to gain deeper insights into understanding tumor metabolism.Jialin Liu Qingce Zang Xinzhu Li Xinyi Tu Ying Zhu Lingzhi Wang Zitong Zhao Yongmei Song Ruiping Zhang Zeper Abliz 2023Chinese Chemical Letters2023,34,11:0
13Non-escaping frost tolerant QTL linked genetic loci at reproductive stage in six wheat DH populations显示文摘Reproductive stage frost poses a major constraint for wheat production in countries such as Australia.However,little progress has been made in identifying key genes to overcome the constraint.In the present study,a severe frost event hit two large-scale field trials consisting of six doubled haploid(DH)wheat populations at reproductive stage(young microspore stage)in Western Australia,leading to the identification of 30 robust frost QTL on 17 chromosomes.The major 18 QTL with the phenotype variation over 9.5%were located on 13 chromosomes including 2 A,2 B,2 D,3 A,4 A,4 B,4 D,5 A,5 D,6 D,7 A,7 B and7 D.Most frost QTL were closely linked to the QTL of anthesis,maturity,Zadok stages as well as linked to anthesis related genes.Out of those,six QTL were repetitively detected on the homologous regions on 2 B,4 B,4 D,5 A,5 D,7 A in more than two populations.Results showed that the frost damage is associated with alleles of Vrn-A1 a,Vrn-D1 a,Rht-B1 b,Rht-D1 b,and the high copy number of Ppd-B1.However,anthesis QTL and anthesis related genes of Vrn-B1 a and Ta FT3-1 B on chromosomes 5 B and 1 B did not lead to frost damage,indicating that these early-flowering phenotype related genes are compatible with frost tolerance and thus can be utilised in breeding.Our results also indicate that wild-type alleles Rht-B1 a and Rht-D1 a can be used when breeding for frost-tolerant varieties without delaying flowering time.Jingjuan Zhang MD Shahidul Islam Yun Zhao Masood Anwar Zaid Alhabbar Maoyun She Rongchang Yang Angela Juhasz Guixiang Tang Jiansheng Chen Hang Liu Yanjie Jiang Shengnan Zhai Xin Hu Junkang Rong Yingquan Zhang Yebo Qin Qier Liu Zitong Yu Yujuan Zhang Sadegh Balotf Mirza Dowla Sonia Afrin Nandita Roy Md Resad Mallik Md Atik Us Saieed Shanjida Rahman Nigarin Sultana Sarah Al-Sheikh Ahmed Chris Florides Kefei Chen Darshan Sharma Nathan Height Ben Biddulph Meiqin Lu Jorge EMayer Wujun Ma 2022The Crop Journal2022,10,1:0
14诱导性多能干细胞的低基因组稳定性使非同源末端连接增加显示文摘背景与目的诱导性多能干细胞(induced pluripotent stem cells,iPSCs)和胚胎干细胞(embryonic stem cells,ESCs)具有许多共同特征,包括相似的形态、基因表达和体外分化谱。然而,iPSCs的基因组稳定性远低于ESCs。在本研究中,我们研究了iPSCs中DNA损伤修复的改变是否为其具有更大诱变倾向的原因。方法将小鼠iPSCs、ESCs和胚胎成纤维细胞暴露于电离辐射(4 Gy),导致双链DNA断裂。照射4 h后使用全基因组重测序评估DNA损伤修复的保真度。我们还分析了分别源自iPSCs或ESCs的小鼠的基因组稳定性。结果照射后,与胚胎干细胞和胚胎成纤维细胞相比,iPSCs具有较低的DNA损伤修复能力,有更多的体细胞突变和短片段插入缺失。iPSCs有更多的非同源末端连接DNA修复和更少的同源重组DNA修复。源自iPSCs的小鼠比ESCs小鼠以及C57对照小鼠的DNA损伤修复能力更低。结论本研究结果部分表明,iPSCs的低基因组稳定性及其在体内的高致瘤性是由DNA损伤修复的低保真度所致。Minjie Zhang Liu Wang Ke An Jun Cai Guochao Li Caiyun Yang Huixian Liu Fengxia Du Xiao Han Zilong Zhang Zitong Zhao Duanqing Pei Yuan Long Xin Xie Qi Zhou Yingli Sun 2019癌症2019,38,8:0
15π-Extented Conjugated Polymers Entailing Pechmann Dye Moieties for Solution-Processed Ambipolar Organic Semiconductors显示文摘In this paper,we report the design,synthesis and semiconducting behavior of two conjugated D-A polymers BPDDTE and BPDBDTE which entail BPD,a Pechmann dye framework,as electron accepting moieties and(E)-1,2-di(thiophen-2-yl)ethane with and without alkyl chains as electron donating moieties.They both show very narrow bandgaps below 1.3 eV.Based on the characterization of the field-effect transistors,thin film of BPDDT exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 0.245 and 0.095 cm^(2)•V^(−1)•s^(−1),respectively,after thermal annealing.Similarly,BPDBDTE with more alkylchains shows ambipolar semiconducting behavior with hole mobility and electron mobilities reaching 0.109 and 0.081 cm^(2)•V^(−1)•s^(−1).Furthermore,BPDBDTE shows good solubilities in several common organic solvents and thus is easily solution-processible.Thus,BPDBDTE is potentially processible with inkjet printing and roll-to-roll printing techniques.Zhengxu Cai Zitong Liu Hewei Luo Penglin Qi Guanxin Zhang Deqing Zhang 2014Chinese Journal of Chemistry2014,32,8:0
16The Control of Intramolecular Through-Bond and Through-Space Coupling in Single-Molecule Junctions显示文摘Electronic coupling between individual building blocks plays an essential role in charge transport through molecular materials and devices.However,the investigation of the transmission mechanism in charge transport via intramolecular coupling remains challenging.Herein,we demonstrate the transition of the intramolecular through-bond and through-space coupling in a single-molecule junction with a family of diketopyrrolopyrrole(DPP)derivative by varying intramolecular donor–acceptor(D–A)interactions.The transition is accomplished by regulating D–A interactions by inserting different aromatic rings inside,leading to two orders of magnitude difference of the single-molecule conductance.The flicker noise analysis demonstrates that the conductance difference arises from the control of the contribution between through-bond and through-space coupling.These findings are further supported by the calculation that the intramolecular coupling among molecular building blocks correlates with the D–A interaction,providing a promising way to regulate the contribution between through-bond and through-space coupling in the charge transport through molecular materials and devices.Zhibing Tan Wenlin Jiang Chun Tang Li-Chuan Chen Liangliang Chen Junyang Liu Zitong Liu Hao-Li Zhang Deqing Zhang Wenjing Hong 2022CCS Chemistry2022,4,2:0
17Recent advances in developing active targeting and multi-functional drug delivery systems via bioorthogonal chemistry显示文摘Bioorthogonal chemistry reactions occur in physiological conditions without interfering with normal physiological processes.Through metabolic engineering,bioorthogonal groups can be tagged onto cell membranes,which selectively attach to cargos with paired groups via bioorthogonal reactions.Due to its simplicity,high efficiency,and specificity,bioorthogonal chemistry has demonstrated great application potential in drug delivery.On the one hand,bioorthogonal reactions improve therapeutic agent delivery to target sites,overcoming off-target distribution.On the other hand,nanoparticles and biomolecules can be linked to cell membranes by bioorthogonal reactions,providing approaches to developing multi-functional drug delivery systems(DDSs).In this review,we first describe the principle of labeling cells or pathogenic microorganisms with bioorthogonal groups.We then highlight recent breakthroughs in developing active targeting DDSs to tumors,immune systems,or bacteria by bioorthogonal chemistry,as well as applications of bioorthogonal chemistry in developing functional bio-inspired DDSs(biomimetic DDSs,cell-based DDSs,bacteria-based and phage-based DDSs)and hydrogels.Finally,we discuss the difficulties and prospective direction of bioorthogonal chemistry in drug delivery.We expect this review will help us understand the latest advances in the development of active targeting and multi-functional DDSs using bioorthogonal chemistry and inspire innovative applications of bioorthogonal chemistry in developing smart DDSs for disease treatment.Wenzhe Yi Ping Xiao Xiaochen Liu Zitong Zhao Xiangshi Sun Jue Wang Lei Zhou Guanru Wang Haiqiang Cao Dangge Wang Yaping Li 2023Signal Transduction and Targeted Therapy2023,8,1:0
18Borophene-ZnO heterostructures:Preparation and application as broadband photonic nonvolatile memory显示文摘High-performance photonic nonvolatile memory which combines data storage and photosensing can achieve low power consumption and ensure computational energy efficiency.Heterostructure has been theoretically and experimentally proved to have synergistic effects between two materials,which can lead to promising electronic and optical properties for advanced optoelectronic devices.Herein,we report the preparation of borophene-ZnO heterostructures and their applications of broadband photonic nonvolatile memory.The memory shows a good switching ratio(5×10^(3))and long-term stability(3,600 s),which are superior to those of the pristine borophene or ZnO quantum dots(QDs).It is found that the memory shows a broad light response from ultraviolet(365 nm)to near infrared(850 nm).Besides,the SET voltage will decrease when the device is exposed to light,which can be attributed to the separation of holes and electrons in accelerating the formation of vacancy conductive filament.This work not only provides a promising material for next-generation photoelectric information,but also paves the way for borophene-based memory towards data storage devices.Runsheng Liu Chuang Hou Xinchao Liang Zitong Wu Guoan Tai 2023Nano Research2023,16,4:0
19Using deep learning to solve computer security challenges:a survey显示文摘Although using machine learning techniques to solve computer security challenges is not a new idea,the rapidly emerging Deep Learning technology has recently triggered a substantial amount of interests in the computer security community.This paper seeks to provide a dedicated review of the very recent research works on using Deep Learning techniques to solve computer security challenges.In particular,the review covers eight computer security problems being solved by applications of Deep Learning:security-oriented program analysis,defending return-oriented programming(ROP)attacks,achieving control-flow integrity(CFI),defending network attacks,malware classification,system-event-based anomaly detection,memory forensics,and fuzzing for software security.Yoon-Ho Choi Peng Liu Zitong Shang Haizhou Wang Zhilong Wang Lan Zhang Junwei Zhou Qingtian Zou 2018Cybersecurity2018,1,1:0
20Regioselectivity of Pd-catalyzed o-carboranearylation: a theoretical view显示文摘The mechanism and the regioselectivity of Pd-catalyzed B(4)–H arylation and B(4,5)–H diarylation foro-carborane with bidentate directing groups were investigated. The complete catalytic cycle involves Pdmediated concerted metalation–deprotonation, oxidative addition, counterion exchange, and reductiveelimination, where counterion exchange is critical. The reductive elimination is the rate- and regioselectivity-determining step for the whole catalytic cycle. B(3)-Arylation is unfavorable because the stericrepulsion between the substituent group on C(2) and the metal moiety would lead to significant distortionof o-carborane and would result in a higher activation energy for reductive elimination. The distortion ofo-carborane can be clearly observed from the change of its aromaticity in the corresponding transitionstates by the calculation of nucleus-independent chemical shifts. Moreover, counterion exchange withcarboxylate before reductive elimination significantly increases the positive charge of palladium, whichleads to a lower activation free energy for the sequential step.Jiying Liu Dongmin Fu Zitong Chen Tiantian Li Ling-Bo Qu Shi-Jun Li Wenjing Zhang Yu Lan 2022Organic Chemistry Frontiers2022,9,6:0
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