Trapping of the coordinatively unsaturated organosilicon anion radical Me3SiCCCCSiMe3− by double ate-complex formation with AIR3

Reaction of 1,4-bis(trimethylsilyl)-1,3-butadiyne with AIR₃ and potassium in THF has led to observation of the first examples of persistent radical di-ate complexes, [(R₃Al)(Me₃Si)CCCC(SiMe₃)(AIR₃)]⁻, which have been characterized by ESR spectroscopy.     

Synthesis of C6-to-C6 and C3-to-C3 diamide linked γ-cyclodextrin dimers

The syntheses of three new diamide-linked γ-cyclodextrin dimers joined by substitution at either a glucopyranose C6^A or C3^A carbon are reported. The syntheses involve the reaction of either C6^A or C3^A amino-substituted γ-cyclodextrin with bis(4-nitrophenyl)succinate to form succinamide linked γ-cyclodextrin dimers or reaction of C6^A azide-substituted γ-cyclodextrin with carbon dioxide to form a urea linked γ-cyclodextrin dimer.     

Rhodium-catalyzed CC coupling of allenes with 3-butenoic acid

Allenes react with 3-butenoic acid under the catalytic action of rhodium(I) complexes to give dienoic acids. While 3-butenoic acid reacts selectively at the terminal carbon atom, allenes can react both at the central and at the terminal carbon atoms of the allenic system. The most important synthetic aspect is that, unlike terminal 1,3-dienes, higher homologues of allene can be caused to react preferentially at the terminal position, thus giving rise to linear 3,6-dienoic acids. Furthermore, the regioselectivity can be reversed using phosphites as ligands in place of phosphines, the major products being branched 3,5-dienoic acids.     

An improved synthesis of the C42–C52 segment of ciguatoxin 3C

In our previously reported method for the construction of the IJKLM-ring of ciguatoxin 3C (CTX3C), the lengthy synthetic process for the intermediate C42–C52 (L-ring) segment was problematic. Therefore, a new and improved procedure for the C42–C52 segment, having modified protecting groups, was developed. The new route includes a chirality transferring Ireland-Claisen rearrangement for the construction of the vicinal dimethyl branching at C47–48, a one-pot cyclization process for the establishment of the stereocenters at C45 and C46 as well as the γ-hydroxy δ-lactone framework corresponding to the L-ring, and Brown’s asymmetric crotylboration for the installation of the stereocenters at C43 and C44. The new C42–C52 segment was successfully coupled with the previously reported C32–C41 (I-ring) segment to produce the IJKLM-ring.     

镍催化构筑C(sp3)—C(sp3)键反应研究进展

过渡金属催化的偶联反应是构筑C-C键的高效方法,在有机合成中得到了广泛的应用.然而,相对于Heck反应、Negishi偶联与Suzuki偶联等构筑C（sp²）-C（sp²）键的反应,过渡金属催化的构筑C（sp³）-C（sp³）键的偶联反应较难进行,发展较晚.近年来,烷基-烷基C-C键偶联反应受到广泛的重视,一些高效催化剂被开发出来,其中镍催化剂展示出独特的催化活性和选择性.本文将综述镍催化烷基-烷基C-C键偶联反应最新研究进展,主要包括烷基亲电试剂与金属有机试剂交叉偶联反应、导向基参与的C（sp³）-H键活化的偶联反应、镍-光反应催化剂协同催化偶联反应、烷基亲电试剂与亲电试剂的还原偶联反应和镍催化烯烃加成反应等.     

强化C3H3元素培养提升学生综合素质

在实验教学中强化C3H3元素,既是培养学生科学素养的重要方法,又是推进素质教育的重要途径,对提高学生的整体素质起着至关重要的作用。本文结合教学实践,就如何在化学实验教学中强化C3H3元素作了一些探讨和尝试。     

晶态C60,K3C60,K6C60的能带计算

本文用紧束缚法的ＥＨＭＯ三维晶体轨道程序进行计算求得了Ｃ６０，Ｋ３Ｃ６０和Ｋ６Ｃ６０的能带结构，并得到了一系列过去未曾见过报导的原子投影态密度、轨道、原子重叠布据、原子电荷、轨道矢量等数据。从这些能带图中可以充分说明三种物质的区别，并可解释Ｋ３Ｃ６０的超导性和Ｃ６０与Ｋ６Ｃ６０的绝缘性。     

Kohlenstoff-haltige ternäre Phasen (Nb3Al2C und Ta3Al2C)

Ohne Zusammenfassung     

Catalytic diastereoselective and enantioconvergent C(sp~3)–C(sp~3) cross-coupling of racemic partners

正Carbon-carbon bond formation is the core of organic synthesis.Transition metal-catalyzed cross-coupling reaction between organohalides and organometallic reagents is one of the most important and straightforward methods for construction of C-C bonds.The catalytic cross coupling between two sp~2-carbon centers,e.g.,aryl-aryl cross-     

Electrochemical NiH-Catalyzed C(sp3)−C(sp3) Coupling of Alkyl Halides and Alkyl Alkenes

Herein, an electrochemically driven NiH-catalyzed reductive coupling of alkyl halides and alkyl alkenes for the construction of Csp³−Csp³ bonds is firstly reported. Notably, alkyl halides serve dual function as coupling substrates and as hydrogen sources to generate NiH species under electrochemical conditions. The tunable nature of this reaction is realized by introducing an intramolecular coordinating group to the substrate, where the product can be easily adjusted to give the desired branched products. The method proceeds under mild conditions, exhibits a broad substrate scope, and affords moderate to excellent yields with over 70 examples, including late-stage modification of natural products and drug derivatives. Mechanistic insights offer evidence for an electrochemically driven coupling process. The sp³-carbon-halogen bonds can be activated through single electron transfer (SET) by the nickel catalyst in its low valence state, generated by cathodic reduction, and the generation of NiH species from alkyl halides is pivotal to this transformation.     

pH_S-3C型数字酸度计的改进

介绍了pHS- 3C型数字酸度计存在的问题及改进措施     

Trimerisierung von Dicyanamid-Ionen C2N3– im Festkörper – Synthesen,Kristallstrukturen und Eigenschaften von NaCs2(C2N3)3 und Na3C6N9 · 3 H2O

Trimerization of Dicyanamide Ions C₂N₃^– in the Solid – Syntheses, Crystal Structures, and Properties of NaCs₂(C₂N₃)₃ und Na₃C₆N₉ · 3 H₂O The Tricyanomelaminate Na₃C₆N₉ · 3 H₂O is obtained by heating NaC₂N₃ to 500 °C and subsequent crystallization from water. According to the single-crystal structure determination (Na₃C₆N₉ · 3 H₂O: P62c; a = 1023.53(8), c = 650.85(15) pm, Z = 2, R1 = 0.0276, wR2 = 0.0710) in the solid cyclic C₆N₉^3– ions occur. Partial ion exchange and crystallization from water yields anhydrous NaCs₂(C₂N₃)₃. The X-ray structure determination (NaCs₂(C₂N₃)₃: P6₃/m, a = 700.01(4), c = 1449.29(7) pm, Z = 2, R1 = 0.0173, wR2 = 0.0432) reveals C₂N₃^– ions in the solid. Calorimetric investigations and detailed IR spectroscopy of NaC₂N₃, Na₃C₆N₉, Na₃C₆N₉ · 3 H₂O, as well as NaCs₂(C₂N₃)₃ reveal in combination with the structure analyses that NaC₂N₃ transforms to Na₃C₆N₉ above 380 °C by trimerization of the C₂N₃^– ions in the solid. Above 180 °C the hydrate Na₃C₆N₉ · 3 H₂O reversibly dehydrates.     

Stereoselective synthesis of C3–C17 and C18–C34 subunits of bullatanocin utilizing α-chloro sulfide intermediates

A convergent synthesis of bullatanocin is envisaged by the union of C18–C34, C3–C17 and the butenolide subunits. The synthesis of the C3–C17 and C18–C34 subunits is disclosed that takes advantage of the chirality of tartaric acid for 1,2-asymmetric induction, chloro sulfides for carbon chain elongation and [2,3] sigmatropic shift for the preparation of 1,4-diol moiety via efficient 1,3-chirality transfer. The THF ring is elaborated by intramolecular displacement.     

Reasons for Selective C–C Bond Rupture upon Photodegradation of the Long-Lived Perfluoro-2,4-dimethyl-3-ethylpentyl-3 Radical

A difference in the mechanisms of photoinduced and thermal decomposition of [(CF₃)₂CF]₂C · C₂F₅ radical was demonstrated on the basis of comparison of experimental results and quantum-chemical calculation data. Irradiation with light of < 320 nm resulted in transition of the radical to an excited state followed by the rupture of the CF₂–CF₃ bond having the greatest length in the ground state. In the thermal degradation of this radical (heating up to 373 K), the rupture >CF–CF₃ bonds is more favorable because of low activation barriers for the process (42–54 kJ/mol). The CF₂–CF₃ bond rupture during thermolysis is unlikely, since the corresponding activation barrier is as high as 84–109 kJ/mol.     

Effect of Cortisol on Caspases in the Co-cultured C2C12 and 3 T3-L1 Cells

The present study was carried out to understand the effect of cortisol on caspase expression in the C2C12 and 3 T3-L1 cells under co-culture system. Cells were co-cultured by using transwell inserts with a 0.4-μm porous membrane to separate C2C12 and 3 T3-L1 preadipocyte cells. Each cell type was grown independently on the transwell plates. Following cell differentiation, inserts containing 3 T3-L1 cells were transferred to C2C12 plates and inserts containing C2C12 cells were transferred to 3 T3-L1 plates. A total of 10 μg/μl of cortisol was added to the medium. Following treatment of cortisol for 3 days, the cells in the lower well were harvested for analysis. Caspases such as caspase 3, caspase 7, and caspase 9 were selected for the analysis. qRT-PCR results indicated the significant increase in the mRNA expression of caspase 3, caspase 7, and caspase 9. Caspase 3, 7, and 9 activities were also increased in the mono- and co-cultured C2C12 and 3 T3-L1 cells. In addition, confocal microscopical investigation indicated that cortisol increases caspase expressions in the mono- and co-cultured C2C12 and 3 T3-L1 cells. Taking all these together, we concluded that the co-culture system reflects the exact effect of cortisol on caspase expression, which is quite distinct from one dimensional mono-cultured experiments.     

晶态Ca3C60与Ca5C60的能带结构研究

用三维EHMO晶体轨道程序分别对Ca3C60，Ca5C60进行了能带结构的计算．计算结果表明，Ca3C60没有导电性，能隙约为0．9eV；而在Ca5C60的能带结构中，费米面刚好穿过半满带，表明Ca5C60是导体；同时在费米面附近有较大的态密度值，表明Ca5C60与K3C60等类似，具有较高的超导转变温度．电荷分析表明，在这两种情况下，钙原子的4s电子基本上全转移到C60上，C60分子可形成一个稳定的带6到10个电子的负离子．     

Stereo selective synthesis of C3–C12 fragment of iriomoteolide-1a

A convergent and flexible synthetic route for the synthesis of C3–C12 fragment of iriomoteolide-1a is described. The key steps are: Mannich reaction, Keck asymmetric allylation, Sharpless asymmetric epoxidation and cross-metathesis protocol.     

Synthetic Studies toward C3‐C9 Segment of Soraphen A1α

The ring‐closure metathesis of the diene (2S,3R,4S)‐1‐(tert‐butyldiphenylsilyloxy)‐2,4‐dimethylhex‐5‐en‐3‐yl acrylate produced the dihydropyrone with the correct stereochemistry for Soraphen A_1α synthesis. The C2,C3 stereocenters were introduced by the addition of the (Z)‐crotyl‐n‐butylstannane to the β‐alkoxyaldehyde(S)‐3‐(benzyloxy)‐2‐methylpropanal in presence of TiCl₄ as a chelating catalyst to give the desired anti,syn homoallyic alcohol (2S,3R,4S)‐1‐(tert‐butyldiphenylsilyloxy)‐2,4‐dimethylhex‐5‐en‐3‐ol.     

The accurate determination of C0–C3 alkylphenol concentrations in crude oils

Accurate determination of the concentrations of volatile and semi-volatile phenols in oils is required to reliably quantify the solute levels that are likely to be loaded into oilfield production waters following partition redistribution. We show, from a gas chromatography–mass spectrometry analysis of a North Sea crude oil, that significantly different concentration data for several C₀–C₃ alkylphenols may be obtained, depending upon whether the response of the fragmentation ion or the molecular ion is used, and whether the data are corrected for the relative response factor (RRF) of individual phenols. We also show how a comparison of concentration data for individual phenols obtained both with and without RRF correction can enable the recognition of co-elution. The accurate quantification of phenols in oils can be used to predict more effectively the requirement for production water-treatment facilities and can provide more reliable inventories of these toxic compounds discharged into the environment. The oil–water partition coefficient of p-cresol increases in crude oils with increasing nitrogen, sulfur, and oxygen-containing (NSO)-compounds. The occurrence of high phenols concentrations and relatively low NSO contents in some condensates may present particular problems in water treatment and disposal.