2,6-二溴代呋喃基-4-对甲苯基吡啶的合成及性质研究

以2-乙酰呋喃和对甲基苯甲醛为原料，氨水为氮源，水/乙醇为溶剂，经Krohnke吡啶合成反应制备了2,6-二呋喃基-4-对甲苯基吡啶。以该化合物为原料，N-溴代丁二酰亚胺为溴化剂，THF为溶剂，三氯化铁为催化剂，在无水无氧条件下经亲电取代反应合成了2,6-二溴代呋喃基-4-对甲苯基吡啶。采用核磁共振氢谱、质谱、紫外可见光谱，分析了2,6-二呋喃基-4-对甲苯基吡啶和2,6-二溴代呋喃基-4-对甲苯基吡啶的结构及光谱性质。结构分析表明，溴代可能发生在两个呋喃环的5号位碳原子上。紫外可见吸收光谱分析发现，2,6-二溴代呋喃基-4-对甲苯基吡啶相对于2,6-二呋喃基-4-对甲苯基吡啶红移了9 nm。这表明溴代后，溴和呋喃环发生p-π共轭，化合物能隙降低，最大吸收波长发生红移。     

咪唑并[1, 2-a]吡啶甲酸衍生物的合成与表征

以3-三氟甲基-2-氨基吡啶为原料,通过NBS选择性溴化,再与溴代丙酮酸甲酯通过“一锅法”进行烷基化-环化反应,之后经选择性氯化、Suzuki偶联反应和水解,合成了咪唑并[1,2-a]吡啶甲酸衍生物。反应总收率达到36.5%。并对Suzuki偶联反应的催化剂和反应条件进行了探讨。     

偶氮蓝褪色光度法测定溴代十六烷基吡啶

基于偶氮蓝与溴代十六烷基吡啶相互作用而导致溶液吸收光谱的变化,用褪色光度法对该体系进行了研究。在pH=5．2的缓冲溶液中,偶氮蓝在531nm波长处有一强的特征吸收峰,当在其溶液中加入溴代十六烷基吡啶后,溶液发生褪色反应,吸光度差值与溴代十六烷基吡啶浓度成正比。最佳条件下,溴代十六烷基吡啶的浓度在0～60μg／25mL范围内遵守比尔定律,检测限（3σ）为0．22μg/mL。方法用于溴代十六烷基吡啶的测定,回收率为97．3％-103．7％。     

氧代-β-紫罗兰酮的合成

在吡啶溴翁和吡啶氯翁离子液[Epy]Br、[Bpy]Br和[Bpy]Cl中,以氯化亚铜为催化剂,叔丁基过氧化氢为氧化剂,可以直接-β-紫罗兰酮选择性氧化合成4-氧代-β-紫罗兰酮,收率可达55%。该方法使用了无毒的氧化剂和催化剂,反应介质和催化剂氯化亚铜可回收再利用,因此是一种有效和环境友好的合成氧代-β紫罗兰酮的方法。     

2-溴-3-氯吡啶的合成研究

吡啶环在农药和医药中发挥了重要作用,卤代吡啶是合成许多药物的重要原料,今年来各种卤代吡啶化合物的合成受到了化学家们的广泛关注。文章介绍了标题化合物的合成方法。以2,3-二氯吡啶为起始原料,经水合肼取代及溴取代两步反应合成了目标化合物,并经MS和1H NMR对其结构进行了表征。本合成路线原料易得、反应时间短、条件温和、操作简便,适合于工业化生产。反应总收率67%。     

3-氯-6-环丙烷基-8-三氟甲基咪唑[1,2-a]吡啶-2-甲酸的合成与表征

以2-氨基-3-三氟甲基吡啶为原料,通过NBS选择性溴化,再与溴代丙酮酸甲酯通过"一锅法"进行烷基化环化反应,之后经选择性氯化、Suzuki偶联反应和水解,合成了咪唑并[1,2-a]吡啶甲酸衍生物——3-氯-6-环丙烷基-8-三氟甲基咪唑并[1,2-a]吡啶-2-甲酸。反应总收率达到36.5%。并对Suzuki偶联反应的催化剂和反应条件进行了探讨。     

溴代十六烷吡啶共振瑞利散射法测定肝素

基于肝素对溴代十六烷吡啶共振瑞利散射的增强作用,建立了一种测定肝素的新方法.在pH值为5.02～8.3的B-R缓冲溶液中,溴代十六烷吡啶与肝素反应形成缔合物,使溶液共振瑞利散射(RRs)增强,以475 nm处的灵敏度最高,它对肝素的检出限(3σ)为0.052 mg/L.研究了适宜的反应条件和影响因素,表明该方法灵敏、稳...     

羟基与酯基官能团化离子液体的合成

以溴代或氯代醇或酯和吡啶为原料合成三个离子液体前体即溴化N-羟乙基吡啶、氯化N-羟己基毗啶和N-甲氧羰乙基吡啶氯代盐;分别将它们与四氟硼酸钠进行复分解反应得到相应的离子液体即N-羟乙基毗啶四氟硼酸盐、N-羟己基毗啶四氟硼酸盐和N-甲氧羰乙基毗啶四氟硼酸盐。利用核磁共振波谱对三个离子液体进行了表征。     

2-氨基-6-溴吡啶的合成研究

2-氨基-6-溴吡啶及其衍生物是重要的药物中间体,以2-氨基-6-甲基吡啶为原料,经重氮化、溴代、氧化、氯化、氨解、霍夫曼降解合成2-氨基-6-溴吡啶。重点考察了氯化、氨解及霍夫曼降解反应条件对收率的影响,总收率34.6%,产品结构经红外、核磁得到确认。     

溴代反应中的选择性溴化剂

综述了四溴环酮，过溴型季铵盐等选择性溴化剂在溴代反应中的应用。     

Reinforcement of the MCFC matrix by Al-based additives: Effect of lithiation

The matrix material in a Molten Carbonate Fuel Cell, usually LiAlO₂, has an important role in the ionic conduction, gas sealing and electrolyte retention. To avoid cracking, this material has been reinforced with various additives, mostly Al-based, which are subject to in situ lithiation. In this work, matrices were systematically synthesized through a fast and more environmentally friendly route and characterized, with two types of reinforcing agent, either Al powder or Al₂O₃ fibers, both with and without carbonates. Then, a comparative analysis was done, in terms of mechanical strength and porosity, on the effect of adding Al powder and Al₂O₃ fibers and their subsequent lithiation. This reaction was found to be quantitative after 50 h at 650 °C, and matrices with reinforcing agent and carbonates featured increased mechanical strength by a factor up to 2 compared to matrices with only reinforcing agent, reaching 0.61 kgf.mm^?2. Al powder was also found to be better suited than Al₂O₃ fibers for addition in a matrix, also contributing to enhance the porosity, particularly after lithiation.     

A new direct formation of benzyllithium reagent on an insoluble polymer

Hydrogen-metal exchange reactions using butyllithium have been studied on cross-linked poly(4-methylstyrene) to prepare polymer-bound benzyllithium reagent, which is a valuable starting material for functionalized resins. A simple one-step lithiation of pendant tolyl group of poly(4-methylstyrene) was achieved with a degree of lithiation as high as 50% using t-butyllithium in tetrahydrofuran.     

In situ oxidation/lithiation of Ni-Co alloy in the molten Li0.62/K0.38 carbonates eutectics

In situ oxidation/lithiation reaction of the pure Ni and Ni-Co alloy electrodes were studied in molten Li_0.62/K_0.38 carbonate eutectics saturated with a 0.9O₂ + 0.1CO₂ atmosphere at 923 K. Ni-Co alloy electrodes were prepared on the pure Au foil by the galvanostatic pulse plating method. Open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were employed to investigate the in situ oxidation /lithiation reaction of electrodes. OCP variation of Ni and Ni-Co alloy electrodes was divided into four regions and charge transfer resistance (R_ct) and diffusion resistance (R_diff) measured as a function of OCP/immersion time in EIS experiment strongly depended on the composition of Ni-Co alloy electrodes and the electrochemical-catalytic activity of Ni-Co alloy electrodes was affected by the surface roughness. In XRD analysis and micro-Raman spectroscopy (RS), the lithiation content increased proportionally with the amount of cobalt in Ni-Co alloy electrodes, which was an important factor to determine the electrochemical-catalytic activity of electrodes.     

The structural evolution and lithiation behavior of vacuum-deposited Si film with high reversible capacity

The silicon film (6 μm) was prepared by vacuum deposition method on a surface modified copper foil as anode for lithium-ion batteries with high capacity and long cycle life. The modified copper foil has a rough and pyramid-like surface which helps the deposited Si film to connect toughly. The deposited hill-like Si is favorable to reduce the mechanical stress coming from the volume expansion and shrinkage of active materials during lithiation and de-lithiation. Moreover, the Si film exists mostly in an amorphous state. After cycling, partial amorphous phase transforms into the polycrystalline Si grains, forming a combination of amorphous and crystalline structure. Cyclic voltammograms (CVs) and electrochemical impedance spectra (EIS) research indicate that the vacuum-deposited thick Si film has a good reversibility of lithiation/de-lithiation. As a consequence, the thick Si film exhibits an excellent cycling performance with high reversible capacity.     

Monolithiation of 5,5′‐Dibromo‐2,2′‐bithiophene Using Flow Microreactors: Mechanistic Implications and Synthetic Applications

The lithiation of 5,5′‐dibromo‐2,2′‐bithiophene with one equivalent of an alkyllithium such as n‐BuLi or s‐BuLi was studied by varying the residence time in flow microreactors. With a short residence time, the product 2,2′‐bithiophene (3) derived from dilithiation was obtained preferentially and a significant amount of the starting material 5,5′‐dibromo‐2,2′‐bithiophene remained unchanged. An increase in the residence time caused a higher yield of the product 5‐bromo‐2,2′‐bithiophene derived from monolithiation with expense in the yields of 2,2′‐bithiophene and 5,5′‐dibromo‐2,2′‐bithiophene. The lithiation using MeLi gave the product 5‐bromo‐2,2′‐bithiophene preferentially even with a very short residence time.     

In situ investigation on deformation and dissolution behavior of porous nickel during its oxidation/lithiation in Li/K2CO3 eutectic

On the basis of previous work, the home-made deformation-testing system was further applied to detect the thickness change of porous nickel materials in the various experimental condition of molten carbonate. The deformation and dissolution behavior of porous nickel and the loading effect on the behavior were in situ studied in the process of oxidation and lithiation. The results indicated that both an obvious deformation and a severe nickel dissolution occurred during the oxidation/lithiation of porous nickel in molten carbonate under loading conditions. Furthermore, the dissolution of nickel from porous nickel was still significant even if without loading. It was found that the deformation of porous nickel closely corresponded to its dissolution during the oxidation/lithiation of porous nickel in molten carbonate.     

In-situ growth flower-like binder-free 3D CuO/Cu2O-CTAB with tunable interlayer spacing for high performance lithium storage

Copper-based oxides are attractive anode materials for lithium-ion batteries (LIBs) due to their abundant resources, low cost, non-toxic and high capacity. However, copper-based oxides will produce a huge volume change during lithiation/delithiation, and the structural strain caused by periodic volume changes may cause the exfoliation of active materials. Herein, a flower-like binder-free three-dimensional (3D) CuO/Cu₂O-CTAB was prepared by introducing CTAB, which homogeneously grew in situ on a copper mesh framework. The binder-free 3D sample guarantees direct contact between the active material and the copper mesh, maintaining the structure stability. The flower-like CuO/Cu₂O-CTAB with a small size reveals larger active interfaces and provides more active sites. The introduction of CTAB enlarges the interlayer spacing of CuO/Cu₂O, increases the active sites for lithium storage, and adapts to the volume change of the material during lithiation/delithiation. In addition, the expanded interlayer structure helps decrease the ion diffusion energy barrier for accelerating electrochemical reaction kinetics. Therefore, CuO/Cu₂O-CTAB exhibits better lithium storage performance (2.9 mAh cm^?2 at 0.5 mA cm^?2) than bare CuO/Cu₂O (1.8 mAh cm^?2 at 0.5 mA cm^?2).     

The synthesis and photochromic properties of two bis(phosphine) ligands based on dithienylethene backbone and their oxides,sulfurets and selenides

A phosphor atom was introduced into photochromic dithienylethene and the corresponding dithienylethene bis(phosphine)ligands were obtained by the lithiation of 1,2-bis-(5-chloro-2-methylthien-3-yl) cyclopentene in the presence of n-butyllithium which were then reacted with Ph₂PCl or Cy₂PCl, respectively. The bis(phosphine)ligands were oxidised with H₂O₂, sulfurated by S₈ and selenated by Se and their structures were characterized.     

Effect of precursor particle size and morphology on lithiation of Ni0.6Mn0.2Co0.2(OH)2

In this paper, Ni_0.6Mn_0.2Co_0.2(OH)₂ precursors with several different morphologies and particle sizes are mixed with Li₂CO₃ and heat treated for 5, 7.5 and 10 h. The effects of the precursor properties on the degree of lithiation, electrochemical properties and volumetric capacities of lithiated product are compared. Based on the characterization results, a small (3 μm), narrow span precursor can be lithiated in a short period of time (5 h) and has good initial discharge capacity (185 mA h g^??1) and capacity retention (93% for 55 cycles). In contrast, a large wide-span precursor requires over 10 h for full lithiation. A highly porous precursor can be lithiated faster than traditional large wide-span materials, and has low cation mixing and good crystallinity. However, the volumetric energy density of porous material is low after lithiation compared to the other tested materials. Capacity retention after washing correlated with crystallographic properties of the sample.

Graphic abstract

     

Preparation of deuterated methyl 6,9,12-octadecatrienoates and methyl 6,9,12,15-octadecatetraenoates

Methyl 6,9,12-octadecatrienoate-15,15,16,16-d ₄ was obtained by Wittig coupling between 6,6,7,7-tetradeutero-3-nonenyltriphenylphosphonium iodide, 8, and the aldehyde ester, methyl 9-oxo-6-nonenoate. Methyl 6-oxohexanoate, obtained by ozonolysis of cyclohexene, was coupled in a Wittig reaction with [2-(1,3-dioxan-2-yl)ethyl]triphenylphosphonium bromide to give methyl 8-dioxanyl-6-octenoate. This compound was transacetalized to methyl 9,9-dimethoxy-6-nonenoate, which was then hydrolyzed to the aldehyde ester. For the preparation of compound 8, the tetrahydropyranyl ether of 2-pentynol was deuterated with deuterium gas and tris-(triphenylphosphine)chlororhodium. The tetradeuterated tetrahydropyranyl ether was converted to the bromide with triphenylphosphine dibromide, and the bromide was coupled with 3-butynol by means of lithium amide in liquid ammonia to give 3-nonynol-6,6,7,7-d ₄. Hydrogenation over Lindlar's catalyst converted the deuterated alkynol to 3-nonenol-6,6,7,7-d ₄. This deuterated alkenol was converted to the bromide with triphenylphosphine dibromide, then to the iodide with sodium iodide in acetone, and finally to 8 with triphenylphosphine in acetonitrile. Methyl 6,9,12,15-octadecatetraenoate-12,13,15,16-d ₄ was obtained by Wittig coupling between methyl 9-oxo-6-nonenoate and 3,4,6,7-tetradeutero-3,6-nonadienyltriphenylphosphonium iodide, 15. For the preparation of compound 15, the bromide obtained from the reaction of 2-pentynol with triphenylphosphine dibromide was coupled with 3-butynol with lithium amide in liquid ammonia. The resulting 3,6-nonadiynol was deuterated with deuterium gas in the presence of P-2 nickel, and the resultant deuterated nonadienol was converted to 15 through the bromide and iodide. The final products were separated from isomers formed during the synthetic sequences by silver resin chromatography.