Catalytic functionalization of unactivated primary C-H bonds directed by an alcohol

New synthetic methods for the catalytic functionalization of C-H bonds have the potential to revolutionize the synthesis of complex molecules. However, the realization of this synthetic potential requires the ability to functionalize selectively one C-H bond in a compound containing many such bonds and an array of functional groups. The site-selective functionalization of aliphatic C-H bonds is one of the greatest challenges that must be met for C-H bond functionalization to be used widely in complex-molecule synthesis, and processes catalysed by transition-metals provide the opportunity to control selectivity. Current methods for catalytic, aliphatic C-H bond functionalization typically rely on the presence of one inherently reactive C-H bond, or on installation and subsequent removal of directing groups that are not components of the desired molecule. To overcome these limitations, we sought catalysts and reagents that would facilitate aliphatic C-H bond functionalization at a single site, with chemoselectivity derived from the properties of the catalyst and site-selectivity directed by common functional groups contained in both the reactant and the desired product. Here we show that the combination of an iridium-phenanthroline catalyst and a dihydridosilane reagent leads to the site-selective γ-functionalization of primary C-H bonds controlled by a hydroxyl group, the most common functional group in natural products. The scope of the reaction encompasses alcohols and ketones bearing many substitution patterns and auxiliary functional groups; this broad scope suggests that this methodology will be suitable for the site-selective and diastereoselective functionalization of complex natural products.     

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...     

多核铜簇合物直接催化活化烃类C-H的研究进展

综述了在双氧水作用下,多核铜簇合物直接催化活化烃类的进展,重点关注在最优催化条件下,多核铜簇合物的催化效果,阐述助催化剂酸可以提高催化活性。     

金属氯化物催化葡萄糖制备5-羟甲基糠醛

用金属氯化物做催化剂,碱金属卤化物做助剂,催化葡萄糖脱水制备5-羟甲基糠醛(5-HMF).在原料与催化剂的质量比为10∶1,原料与助催化剂的质量比为1∶1的情况下,考察金属氯化物、助剂、溶剂、温度、时间对5-HMF收率的影响.结果显示:Al Cl3做催化剂、Na I做助剂、溶剂为N,N-二甲基乙酰胺(DMAC)、反应温度为130℃、反应时间为15 min时5-HMF收率可达30.6%.     

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.     

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.     

Understanding and exploiting C-H bond activation

The selective transformation of ubiquitous but inert C H bonds to other functional groups has far-reaching practical implications, ranging from more efficient strategies for fine chemical synthesis to the replacement of current petrochemical feedstocks by less expensive and more readily available alkanes. The past twenty years have seen many examples of C-H bond activation at transition-metal centres, often under remarkably mild conditions and with high selectivity. Although profitable practical applications have not yet been developed, our understanding of how these organometallic reactions occur, and what their inherent advantages and limitations for practical alkane conversion are, has progressed considerably. In fact, the recent development of promising catalytic systems highlights the potential of organometallic chemistry for useful C-H bond activation strategies that will ultimately allow us to exploit Earth's alkane resources more efficiently and cleanly.     

聚丙烯酰胺在炭黑粒子表面的功能修饰及其负蒸气系数效应

以硝酸铈铵/CB-CH2OH或硝酸铈铵/CB-C(CH3)2OH为氧化还原引发体系,在炭黑(CB)表面接枝了聚丙烯酰胺(PAAm-g-CB);通过PAAm-g-CB存在下的异丙醇铝(AIP)溶胶-凝胶化反应,制得一种新的具有智能响应性的PAAm-g-CB/Al2O3凝胶杂化材料,研究了其气敏和湿敏性能.结果表明,该杂化材料在其良溶剂蒸气中电阻急剧下降,呈现负蒸气系数现象(NVC);而在不良溶剂蒸气中电阻几乎不发生变化.其响应性能与杂化体间氢键作用密切相关,并受接枝率大小的影响.     

金属卤化物／硅胶型催化剂在傅克反应的催化活性

研究了一种以硅胶为载体,负载金属氯化物的新型固体酸催化剂,测试了在烷基化反应中的催化活性,通过对催化剂的XRD,TG－DTG测试表征,结果表明,制备中硅胶的孔径、负载量、活化温度对催化剂结构和活性有显著影响。     

石墨烯的制备、功能化及应用

石墨烯自发现以来,以其独特的结构和优越的性能,吸引了物理、化学、材料学等各领域的关注,成为当前研究热点之一.介绍了石墨烯的制备方法,并比较各种方法的优劣性.探讨了石墨烯的共价和非共价功能化方法.评述了石墨烯在生物医学及其他领域中的应用.     

针穿刺软组织实验与穿刺力力学建模

通过针穿刺软组织实验,得出针穿刺软组织过程中穿刺力随位移变化的数据。在分析穿刺力与位移之间关系的基础上,选取非线性弹簧模型和二阶多项式模型对穿刺力进行最小二乘法拟合,得到穿刺力的力学模型。     

催化动力学法同时测定铬和钼

以Ｈ２Ｏ２氧化Ｉ＾－作为指示反应，可用催化动力学法通过一次实验同时测定铬和钼，由于铬催化反应的表观反应级数不是常数，因而用多元线性回归法得到的结果误差较大。用主成份回归法由于不需要严格的数学模型，因而可得到满意的结果。     

催化热分解法纳米碳管的制备与提纯

通过催化热分解法制备了多壁纳米碳管,研究了制备纳米碳管的最佳实验条件·对制备的纳米碳管进行了提纯实验·应用X射线衍射、透射电镜对自制的原料纳米碳粉进行了粒度测定、形貌观察·纳米碳粉为球形颗粒,粒度为50～80nm·应用透射电镜对纳米碳管进行了形貌观察,纳米碳管为定向生长,直径在20～30nm之间·在1000℃,1.5h时,得到了较高收率,纯净的碳纳米管·     

催化萃取光度法测定邻氨基酚

本文研究了在 ｐＨ５．５的弱酸性介质中，利用铁（Ⅲ）催化过氧化氢氧化邻氨基酚显色的反应，用氯仿萃取有色产物，通过测量４２４ｕm下有机相的吸光度，建立了催化萃取光度法测定邻氨基酚的新方法．方法的线性范围为 ０．５０～２０μｇ／ｍｌ，检出限为 ２ ２× １０－８ｇ／mｌ．用于合成水样中邻氨基酚的测定，结果满意．     

催化动力学光度法测定痕量锰

研究了在ＮａＡｃ介质中,利用Ｍｎ（Ⅱ）催化溶解氧氧化溴邻苯三酚红褪色的指示反应,建立了催化动力学光度法测定痕量锰的新方法,方法的线性范围为０～０１０ｕｇ／２５ｍｌ和０１０－１．０ｕｇ／２５ｍｌ,检出限为９．９×１０－１１ｇ／ｍｌ,用于水和茶叶中Ｍｎ的测定,结果满意．     

催化氨氧化合成2,6-二氯苯甲腈

研究了以２,６－二氯甲苯为原料,催化氨氧化合成２,６－二氟苯甲腈,制备和筛选了性能优良的 Ｐ－Ｖ－Ｍｏ－Ｃｒ－Ｋ－Ｏ／γ－Ａｌ２Ｏ３氨氧化反应催化剂。经过 ２４０ ｈ催化剂寿命的初步实验,催化剂活性、选择性不降低。在 φ３２ ｍｍ×３ ｍｍ单管反应器中进行了氨氧化反应条件优化研究,反应温度 ３６０ Ｃ,接触时间 １０ Ｓ,氧气对 ２,６－二氯甲苯物质的量比为３时,２,６－二氯甲苯转化率９２．２％,２,６－二氯苯甲腈收率７７．６％,纯度为９８．７％。     

催化光度法测定痕量硫氰酸根

在磷酸介质中, 硫氰酸根对溴酸钾氧化茜素红的褪色反应具有较强的催化作用, 据此建立了催化光度法测定痕量硫氰酸根的新方法。在选定的条件下, 方法的检出限为１．１×１０－ ９ｇ／ ｍ Ｌ, 测定范围为０．０４５ ｍ ｇ／Ｌ～０．６４ ｍ ｇ／Ｌ, 用于直接测定唾液、湖水中的硫氰酸根, 结果满意。     

相转移催化法制备羧甲基壳聚糖

用相转移催化剂制备羧甲基壳聚糖，研究了反应时间，温度，碱浓度和投料比等工艺条件对羧甲基化程度及产物收率的影响，结果表明，使用相转移催化剂，反应时间缩短到3h，羧甲基壳聚糖取代度和收率分别达到0.92和84.42%。     

用催化动力学分析法同时测定多种组分

多种催化剂催化同一指示反应时，如果其反应的表观机理不同，则可由一次实验同时测定这几种催化剂，文中以锇和碘的两元体系例，以Ｃｅ（Ⅵ）氧化Ａｓ（Ⅲ）作为指示反应，研究了这两种组分的同时测定方法，用光度法测量Ｃｅ（Ⅵ）浓度随时间的变化，然后用Ｓａｖｉｔｚｋｙ－Ｇｏｌａｙ方法求出其反应速率，表观反应速率常数及反应级数可用线性回归法求出，并用两元线性因归计算锇和碘的浓度。