C-H bond amination by iron-imido/nitrene species

C-H amination by iron-imido/nitrene species has attracted increasing research interest in recent years because of its potential use in economical and environmentally benign syntheses of amino compounds.With the aim of providing a comprehensive overview of this field,which is of interest to both the synthetic organic and inorganic communities,this paper reviews the status quo of C-H amination chemistry by iron-imido/nitrene intermediates,as well as by well-defined iron-imido/nitrene compounds,with special emphasis on their structure/reactivity correlations.Achievements,problems,and perspectives in this growing field are discussed.     

Density functional theory calculation on the C―H bond insertion reaction of dibromocarbene with acetaldehyde

The insertion reaction mechanism of CBr2 with CH3CHO has been studied by using the B3LYPI6-31G（d） method. The geometries of reactions, transition state and products were completely optimized. All the energy of the species was obtained at the CCSD（T）/6-31G（d） level. All the transition state is verified by the vibrational analysis and the internal reaction coordinate （IRC） calculations. The results show that the propionaldehyde （Hp1） is the main product of CH2 insertion with CH3CHO. The calculated results indicated that all the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CBr2 not only can insert the Cα-H [reaction I（1）]） but also can react with Cβ-H [reaction l1（1）]. The statistical thermodynamics and Eyring transition state theory with Wigner correc-tion are used to study the thermodynamic and kinetic characters of I（1） and I1（1） in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature rang is 250 to 1750 K and 250 to 1600 K at 1.0 atm for I（1） and I1（1） respectively. The rate constant and equilibrium constant are distinct in the range from 250 to 1000 K so that I（1） more easily occurs, while the reactions are not selected in the temperature range of 1000-1600 K.     

气相中Zr活化CH_4分子C—H键的理论研究

采用密度泛函理论和高级电子相关耦合簇方法,在CCSD/6-311++G(3df,3pd)//B3LYP/6-311++G(3df,3pd)理论水平下,研究了两个自旋态下的Zr原子活化CH4分子中C—H键逐个夺取H原子的微观反应机理.通过计算,讨论了势能面交叉和可能的自旋翻转过程.用Harvey等的方法优化出最低能量交叉点(MECP),并计算了MECP处相应的自旋-轨道耦合常数(SOC),进一步讨论了Zr与CH4的反应中不同势能面之间的"系间窜越"(ISC)的可能性.     

The consideration and choice on exploiting energy source

A problem of petroleum energy crisis will probably be faced in the late 21st century. It is impossible to discover the giant oil fields again based on the traditional knowledge and theory of petroleum geology. From the global development point of view as well as the situation in China, the five choices of energy source in the future are to (i) extend the field of exploration in conventional petroleum and natural gas source, and exploit oil-gas source in ocean and some basins of northwestern China; (ii) discover unconventional oil and natural gas source: abiogenic gas, deep oil and gas, gas hydrates, coal bed gas and so on; (iii) develop techniques of cleansing, gasifying and liquefying coal for highly effective utilization, and transform coal into electricity and at the same time pay attention to the environment protection and pollution control as well; (iv) carry out researches on the theory and technology of producing and storing hydrogen in order to seek for its effective and economical utilization; (v) pay attention to and carry out the research in advance on exploiting the source of³He isotope on the moon and using the D-³He controlled nuclear fusion as fuel.     

基于空频分集的合作通信协议

为了提高无线通信的有效性和可靠性,提出了一种基于空频分集的合作通信协议.它通过联合利用传输频带间的衰落不相关特性和中继链路间的衰落不相关特性,获得更高的分级和复接增益.仿真结果表明: 该协议的分集增益为3, 而复接增益为1, 优于选择中继和附加中继协议.当中断概率低于10-2时,该协议可以获得至少3 dB的信噪比增益.利用频率分集能够有效提高合作通信的性能.     

开发多媒体CAI课件的研究与实践

以制作完成的"历代书法名迹欣赏"课件为例,介绍用Authorware4.0开发多媒体辅助教学软件的一些方法和体会.     

Weak interaction between CH3SO and HOCl: Hydrogen bond, chlorine bond and oxygen bond

B3lyp/6-311＋＋g＊＊ and mp2/6-311＋＋g＊＊ calculations were used to analyze the interaction between CH3SO and HOCl. Nine （complex A： S1A-S9A） and five （complex B： S4B-S7B and S10B） minima were localized on the potential energy surface of CH3SO…HOCl complexes at b3lyp/6-311＋＋g＊＊ and mp2/ 6-311＋＋g＊＊ computational levels, respectively. The AIM and NBO theories were also applied to explain the nature of the complexes. Bonding energy of complexes A and B corrected with BSSE falls in the ranges of -0.4―-41.4 kJ·mol-1 and -6.9―-35.8 kJ·mol-1 at mp2/6-311＋＋g＊＊ level, respectively. The re- sults show that a novel oxygen bond complex （S6） exists in the system, besides hydrogen bond and chlorine bond. Especially, S6B-F, S6B-Br and S7B are blue shifted complexes compared with red shifted S6A, because the electron transfer occurs between LP1（S8） and σ＊（O5-Cl7）, resulting in the increase of O5-Cl7 and the decrease of vibrational frequency. The complex of S10B has characteristics of both red shift and blue shift.     

石油与天然气开采引起的地表下沉预测

石油与天然气开采导致油气层中地下压力的减少，造成油气层的压密。当压密的数值达到一定量时，会引起地表下沉。本文主要介绍了油气开采引起地表下沉的机理和下沉危害，把油气开采引起的地表移动视为随机过程，以整个开采区域为研究对象，提出了下沉源函数和下沉传播分布函数，建立了开采引起地表下沉的预测模型，为研究油气开采引起的地表沉陷损害问题提供了理论依据。     

利用无线传播信道的安全空时网络编码

提出一种基于物理信道的安全空时网络编码方案。该方案利用信道互易性,将合法发送者和接收者之间共同的有效信道衰落系数作为安全密钥源。合法收发节点利用它们之间的信道生成密钥,并根据生成的密钥确定发送信号的旋转角度。旋转角度来自与发送符号相同的星座,使得旋转之后的符号仍然属于原来的星座点集合。由于窃听节点与合法收发对之间的信道是互相独立的,因此窃听节点很难获得合法收发节点之间的密钥。基于上述的星座旋转,所提安全空时网络编码能够保证各中继节点在异步传输的前提下,目的节点仍然获得满分集,而窃听节点不能获取任何有用信息。仿真结果验证了安全空时网络编码方案的合理性。     

S-Tracker:基于栈异常的shellcode检测方法

根据shellcode的API函数及系统调用对栈帧的影响,定义了EBP异常、Ret异常和长度异常,并在此基础上提出了基于栈异常的shellcode检测方法——S-Tracker.该方法遍历特定敏感API函数的栈帧链、检测异常、定位漏洞函数和Shellcode代码,并采用栈帧重构解决了栈帧中的EBP缺失或破坏的问题.实验结果表明:S-Tracker能有效检测到基于普通shellcode、混合型shellcode以及纯ROP shellcode的攻击行为,具备追踪shellcode分布区域和EIP跳转函数的功能,且其性能开销较小、没有误报;与微软EMET工具相比,STracker在内核层实现,更加难以被攻击者绕过.     

Catalytic C-H functionalization by metal carbenoid and nitrenoid insertion

Novel reactions that can selectively functionalize carbon-hydrogen bonds are of intense interest to the chemical community because they offer new strategic approaches for synthesis. A very promising 'carbon-hydrogen functionalization' method involves the insertion of metal carbenes and nitrenes into C-H bonds. This area has experienced considerable growth in the past decade, particularly in the area of enantioselective intermolecular reactions. Here we discuss several facets of these kinds of C-H functionalization reactions and provide a perspective on how this methodology has affected the synthesis of complex natural products and potential pharmaceutical agents.     

多媒体教学课件开发中的关键技术

本就多媒体教学课件开发过程中几个关键技术进行了探讨，提出了设计过程中应注意的一些问题和应遵循的原则，以此来保证多媒体教学课件开发的质量和性能。     

Focusing transform-based direction-of-arrival method exploiting multi-cycle frequencies

When single cycle frequency is employed, the existing spectral correlation-signal subspace fitting (SC-SSF) algorithms usually contain two disadvantages: those single-cycle estimators cannot reach the best performance; it is inconvenient to be applied in practice since the right cycle frequency has to be selected. Based on the Jacobi-Anger expansion and the idea of focusing transform, a new approach exploiting multi-cycle frequencies of cyclostationary signal is discussed in this paper. Simulation results demonstrate the effectiveness of the new method.     

Chiral CpxRh complexes for C-H functionalization reactions

Transition-metal-catalyzed C-H functionalization is becoming a general and straightforward strategy for the construction of car-bon-carbon and carbon-heteroatom...     

山西旅游资源开发的潜力及其战略构想

山西的旅游源 ,无论是类型、数量或质量 ,都有自己明显的优势。山西的旅游资源具有丰富的文化内涵 ,蕴藏着巨大的开发前景。在分析山西旅游资源大有潜力的基础上 ,进一步提出了跨世纪的山西旅游发展战略     

钯催化多氟芳烃C-H键活化反应的研究

多氟联苯类化合物广泛用于药物、有机发光二极管和液晶材料等分子骨架结构中,因此,对于多氟联苯类化合物的有效合成具有重要的意义。本文通过利用过渡金属钯催化卤代芳烃与多氟芳烃C-H键活化反应,实现了芳基C-C键的有效构建,获得最佳反应条件为:10 mol%Pd(OAc)2,20 mol%PCy3作为配体,1.0 mmol五氟苯,0.5mmol 4-甲基溴苯,1.2当量的Cs2CO3做碱,1 m L甲苯为溶剂,反应温度为80℃或110℃。该体系具有反应条件温和,底物适用范围广,原料廉价易得等优点。     

西部开发中的内蒙古草原畜牧业

中央把生态建设和环境保护作为西部开发的切入点 ,既切合西部地区生态环境严重恶化的实际 ,又符合马克思生产力理论。生态环境和人口是生产力的源泉。就整体而言 ,蒙古高原不宜耕种 ,但人们却在这里一直开展着大规模的农业活动。结果 ,已经造成了草原的严重沙化退化 ,破坏了生态环境 ,破坏了作为生产力源泉的生态环境和人口之间的均衡协调关系。因此 ,内蒙古应该抓住西部开发的有利时机 ,不宜耕种的耕地还草还林 ,大力发展适合内蒙古自然地理条件的草原畜牧业。通过转变观念、创新制度 ,逐步解决我区草原畜牧业的发展中面临的人口压力大、草原生态环境恶化、资金投入不足、品种改良滞后、管理体制不顺等问题。同时 ,通过草原畜牧业的产业化发展 ,实现草原畜牧业与市场经济制度接轨 ,使草原畜牧业在我区草原绿色经济发展战略中发挥应有的作用。     

芳香碳氢键的活化官能化研究进展

目前已发现多种过渡金属络合物可以实现芳香C—H键的活化.例如Pd,Ru,Rh,Cu,Ni,Fe等的络合物都能够实现导向或非导向的各种芳香C—H键活化官能化.对近年来过渡金属催化的芳香C—H键活化构建C—C键反应进展进行了综述.     

知生知死知我——“子曰：‘未知生焉知死？’”简论

“生”与“死”是孔子学说中没有明言的问题，通过遮诠的表述，孔子表达了对“生”、“死”问题上采用对象化把握方式的反对。孔子对“知生”与“知死”割裂表诠，意在通过不可言说的言说，达到对“知生”与“知死”本是同一过程的领悟。在此领悟中，此在退回到本真能在。知生即为知死，知死即为知我。