Substituent effects in addition of iodine thiocyanate to alkenes

The plots of logarithms of relative rates of ISCN addition to alkenes versus alkene IPs and versus alkene HOMO energies reveal that the alkene relative reactivity depends upon both electronic and steric effects of the substituents. Steric effects are related not only to the degree of substitution on the CC bond but also to the relative position, size, and branching of alkyl substituents.     

Telomerization and dimerization of isoprene by in situ generated palladium-carbene catalysts

The palladium-catalyzed telomerization of isoprene with methanol and dimerization of isoprene have been studied in presence of in situ generated palladium-carbene catalysts. Unprecedented catalyst productivity has been observed for these two reactions. A selectivity switch from the telomer to the dimer product occurred by using different substituted carbene ligands. Among the imidazolium salts tested 1,3-dimesitylimidazolium mesylate (1), 1,3-dimesityl-4,5-dihydroimidazolium chloride (3) gave the best yields for telomerization reaction whereas 1,3-bis-(2,6-diisopropylphenyl)-4,5-dihydroimidazolium tetrafluoroborate (5) and 1,3-bis-(2,6-diisopropylphenyl)-4,5-dimethyl-4,5-dihydroimidazolium chloride (9) form dimers in high yield and good selectivity.     

Metallic samarium and iodine promoted facile and efficient syntheses of trisubstituted alkenes from the acetates of Baylis-Hillman adducts

Promoted by samarium metal in the presence of a catalytic amount of iodine, the Baylis-Hillman adducts underwent reductive elimination to form (E)-methylcinnamic ester derivatives. When the iodine was used in 1:1 ratio with metallic samarium, stereospecific syntheses of allylic iodide derivatives, (2Z)-2-(iodomethyl)alk-2-enoates, were achieved. Thus, this gives a new approach to the selective construction of stereo-defined trisubstituted alkenes with the simple Sm/I₂ system.     

Intramolecular hydroamination catalysed by Ag complexes stabilised in situ by bidentate ligands

A series of silver complexes generated in situ from AgOSO₂CF₃ (AgOTf) and a range of bidentate ligands were investigated as catalysts for the intramolecular hydroamination of 4-pentyn-1-amine. A variety of P- and N-donor ligands were tested including the novel pyrazole-phosphine ligand 1-(2-(diphenylphosphino)phenyl)pyrazole. The best catalyst was formed from equimolar amounts of the P,N-donor ligand 1-(2-(diphenylphosphino)ethyl)pyrazole and AgOTf, which achieved a turnover rate of 129 h⁻¹ for the cyclisation of 4-pentyn-1-amine.     

Iodofluorination of alkenes and alkynes promoted by iodine and 4-iodotoluene difluoride

It was found that a mixture of molecular iodine and 4-iodotoluene difluoride are useful to generate in situ the couple ‘IF’ that was able to add in a Markovnikov fashion and with prevalent anti-stereoselectivity to various alkenes and alkynes.     

Synthesis,electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new phthalocyanines peripherally fused to four flexible crown ether moieties

Novel Ni(II), Zn(II), Co(II) and Cu(II) phthalocyanines with four peripheral 4-[methyleneoxy(18-crown-6)] groups have been synthesized via the cyclic tetramerization of 4-[{(18-crown-6)-yl}methyleneoxy]phthalonitrile and the corresponding metal salts (NiCl₂, Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The thermal stabilities of the metal-free and metallophthalocyanine compounds were determined by thermogravimetric analysis. The structures of the target compounds were confirmed using elemental analysis, IR, ¹H-NMR, ¹³C-NMR, UV–Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while the cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, the metal-free, nickel, zinc and copper phthalocyanines show only ring-based reduction and oxidation processes. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes.     

Flexible NH3 sensors fabricated by in situ self-assembly of polypyrrole

Novel flexible NH₃ gas sensors were formed by the in situ self-assembly of polypyrrole (PPy) on plastic substrates. A negatively charged substrate was prepared by the formation of an organic monolayer (3-mercapto-1-propanesulfonic acid sodium salt—MPS) on a polyester (PET) substrate using a pair of comb-like Au electrodes. Two-cycle poly(4-styrenesulfonic acid) sodium salt/poly(allylamine hydrochloride) (PSS/PAH) bilayers (precursor layer) were then layer-by-layer (LBL) deposited on an MPS-modified substrate. Finally, a monolayer of PPy self-assembled in situ and PPy multilayer thin films self-assembled LBL in situ on a (PSS/PAH)₂/MPS/Au/Cr/PET substrate. The thin films were analyzed by atomic force microscopy (AFM). The effects of the precursor layer (PSS), the deposition time of the monolayer of PPy and the number of PPy multilayers on the gas sensing properties (response) and the flexibility of the sensors were investigated to optimize the fabrication of the film. Additionally, other sensing properties such as sensing linearity, reproducibility, response and recovery times, as well as cross-sensitivity effects were studied. The flexible NH₃ gas sensor exhibited a strong response that was comparable to or even greater than that of sensors that were fabricated on rigid substrate at room temperature.     

二维离子色谱法同时测定环境水样中的碘离子、硫氰酸根和高氯酸根

建立了二维离子色谱法同时测定环境水样中的碘离子、硫氰酸根离子和高氯酸根离子的方法。先采用常规阴离子色谱柱(IonPac AS16, 250 mm×4 mm)将水样中的碘离子、硫氰酸根离子和高氯酸根离子与干扰离子进行分离。样品溶液通过抑制器后,将含有碘离子、硫氰酸根离子和高氯酸根离子的淋洗液导入富集柱(MAC-200, 80 mm×0.75 mm),再通过毛细管阴离子色谱柱(IonPac AS20 Capillary, 250 mm×0.4 mm)进行分离和定量分析。方法的线性范围为0.05～100 μg/L,相关系数达到0.9999,检出限为0.02～0.05 μg/L。样品中碘离子、硫氰酸根离子和高氯酸根离子的加标回收率在85.1%～100.1%之间,回收率的相对标准偏差(RSD)(n=6)在1.7%～4.9%之间。该法试剂用量小,灵敏度比常规离子色谱提高30～40倍,同时去除了样液中的高浓度基体杂质,适用于水样中低含量碘离子、硫氰酸根离子和高氯酸根离子的检测。     

Thermal and mechanical properties of in situ polymerized PS/EPDM blends

In situ polymerized PS/EPDM blends were prepared by dissolving poly(ethylene-co-propylene-co-2-ethylidene-5-norbornene) (EPDM) in styrene monomer, followed by bulk polymerization at 60 °C and 80 °C . EPDM has excellent resistance to such factors as weather, ozone and oxidation, attributed to its non-conjugated diene component, and it could be a good alternative for substituting polybutadiene-based rubbers in PS toughening. The in situ polymerized blends were characterized by dynamic mechanical analysis, thermogravimetric analysis, gel permeation chromatography, and tensile and Izod impact resistance tests. The PS/EPDM blends are immiscible and present two phases, a dispersed elastomeric phase (EPDM) in a rigid PS matrix whose phase behavior is strongly affected by the polymerization temperature. Mechanical properties of the blends are influenced by the increase in the average size of EPDM domains with the increase in the polymerization temperature and EPDM content. The blends polymerized at 60 °C containing 5 wt% of EPDM presents an increase in the impact resistance of 80% and containing 17 wt% of EPDM presents an increase in the strain at break of 170% in comparison with the value of PS. The blend polymerized at 80 °C containing 17 wt% of EPDM presents an increase in the strain at break of 480% and in impact resistance of 140% in comparison with the value of PS.     

Synthesis of polylactide/clay nanocomposites by in situ intercalative polymerization in supercritical carbon dioxide

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted onto the clay surface, leading to an exfoliated morphology. Nanocomposites with high clay contents (30-50 wt.%), called masterbatches, have also been successfully prepared and were recovered as fine powders thanks to the unique properties of the supercritical fluid. Dilution of these masterbatches into commercial l-polylactide by melt blending has led to essentially exfoliated nanocomposites containing 3 wt.% of clay. The mechanical properties of these materials have been assessed by flexion and impact tests. Significant improvements of stiffness and toughness have been observed for the PLA/clay nanocomposites compared to the pure matrix, together with improved impact resistance.     

Degradation and thermal properties of in situ compatibilized PS/POE blends

This paper reported the degradation behaviors and thermal properties of polystyrene (PS)/polyolefin elastomer (POE) blends with AlCl₃ as the catalyst of Friedel-Crafts alkylation reaction. Gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) were adopted to reveal the effects of in situ grafting reaction and degradation of blending compounds on the thermal properties of PS/POE blends. It was found that the changes in both catalyst content and blend composition influenced the competition between in situ grafting reaction and degradation, resulting in the complexity of the thermal properties of PS/POE/AlCl₃ blends.     

Temperature-controlled divergent synthesis of 4-alkoxy- or 4-alkenyl-chromanes via inverse electron-demand cycloaddition with in situ generated ortho-quinone methides

The temperature-controlled divergent synthesis of 4-alkoxy- or 4-alkenyl-chromanes via inverse electron-demand cycloaddition with in situ generated ortho-quinone methides under identical reaction conditions except for thermal condition has been developed. At room temperature, the reaction generated 4-methoxychromanes, whereas the reaction performed at room temperature to 100?°C gave 4-alkenylchromanes. Trifluoromethanesulfonic acid was efficiently suitable in the reaction to give the 4-substituted chromanes. This divergent synthetic strategy exhibits a new method giving carbon–carbon or carbon–oxygen bond by controlling the reaction temperature.     

Synthesis, crystal structures and properties of three new mixed-ligand d metal complexes constructed from pyridinecarboxylate and in situ generated amino-tetrazole ligand

Three new metal-organic frameworks, [Zn(atz)(nic)]_n(1), [Zn(atz)(isonic)]_n·nHisonic(2) and [Cd(atz)(isonic)]_n(3) (Hnic=nicotinic acid, Hisonic=isonicotinic acid), have been firstly synthesized by employing mixed-ligand of pyridinecarboxylate with the in situ generated ligand of 5-amino-tetrazolate(atz⁻), and characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction. The results revealed that 1 presents a two-dimensional (2D) “sql” topological network constructed from the linear chain subunit of Zn(nic)₂ and atz⁻ ligand. A remarkable feature of 2 is a 2-fold interpenetrated diamondoid network with free Hisonic molecules locating in the channels formed by the zigzag chain subunits of Zn(isonic)₂. Complex 3 is a 3D non-interpenetrated pillared framework constructed from the double chain subunits of Cd-COO⁻-Cd. It possesses a rarely observed (4,6)-connected “fsc” topology. The thermal stabilities and fluorescent properties of the complexes were investigated. All of these complexes exhibited intense fluorescent emissions in the solid state at room temperature.     

Determination of tellurium by hydride generation with in situ trapping flame atomic absorption spectrometry

The analytical performance of coupled hydride generation — integrated atom trap (HG-IAT) atomizer flame atomic absorption spectrometry (FAAS) system was evaluated for determination of Te in reference material (GBW 07302 Stream Sediment), coal fly ash and garlic. Tellurium, using formation of H₂Te vapors, is atomized in air–acetylene flame-heated IAT. A new design HG-IAT-FAAS hyphenated technique that would exceed the operational capabilities of existing arrangements (a water-cooled single silica tube, double-slotted quartz tube or an “integrated trap”) was investigated. An improvement in detection limit was achieved compared with using either of the above atom trapping techniques separately. The concentration detection limit, defined as 3 times the blank standard deviation (3σ), was 0.9 ng mL^− 1 for Te. For a 2 min in situ pre-concentration time (sample volume of 2 mL), sensitivity enhancement compared to flame AAS, was 222 fold, using the hydride generation — atom trapping technique. The sensitivity can be further improved by increasing the collection time. The precision, expressed as RSD, was 7.0% (n = 6) for Te. The designs studied include slotted tube, single silica tube and integrated atom trap-cooled atom traps. The accuracy of the method was verified using a certified reference material (GBW 07302 Stream Sediment) by aqueous standard calibration curves. The measured Te contents of the reference material was in agreement with the information value. The method was successfully applied to the determination of tellurium in coal fly ash and garlic.     

Development of a versatile rotating ring-disc electrode for in situ pH measurements

There are some electrocatalytic reactions in which the key parameter explaining their behavior is a local change in pH. Therefore, it is of utter importance to develop an electrode that could quantify this parameter in situ, but also be customizable to be used in different systems. The purpose of this work is to build a versatile rotating ring/disc electrode (RRDE) with IrO_x deposited on a glass tube as a ring and any kind of material as disc. As the IrO_x is sensitive to pH variation, the reactions promoted on the disc can trigger proportional pH shifts on the ring. In such assembly, the IrO_x ring presents a fast response time even during the pH transients due to the small thickness of the ring (approximately 10 μm), which enables the detection of interfacial pH changes. The ring electrode was tested toward the interfacial pH shift observed during the electrolytic reduction of water on the disc and also characterized by acid–base titration to determine the response time. As the main conclusions, fast response and durable RRDE were obtained, and this assembly could be used to revisit many electrocatalytic reactions in order to test the importance of local pH on the process.     

Formation of benzo[c]thiophen-1-aminium iodide by the reaction of o-alkynylbenzothioamide with iodine

Reaction of o-alkynylbenzothioamide with molecular iodine was investigated. Unique benzo[c]thiophen-1-aminium iodide was obtained when the tertiary thioamide was used as a reactant. The reaction proceeded efficiently in less polar solvent, whereas the corresponding product was also obtained in a polar solvent. Single crystal X-ray analysis revealed that the benzo[c]thiophen-1-aminium structure possesses a resonance structure in N–C–S bond. Its stabilization shows a clear difference in the result from the reaction of amide analogue with iodine to give no stable compound.     

Differential in situ sensing of extra- and intracellular glutathione by a novel redox-responsive silica matrix-Au nanoprobe

We synthesized a biothiol-sensitive nanoprobe by assembling gold nanoparticles with a novel redox-responsive silica (ReSi) matrix using dithiobis (succinimidyl propionate) and (3-aminopropyl) trimethoxysilane. Thin layer disulfide-bonded networks of the ReSi could differentially respond to extra- and intracellular glutathione in cancer cells within 30 min; furthermore, targeted cellular uptake could be monitored in situ by fluorescence recovery. Sigmoidal dose–response pattern of the nanoprobes presented in this study were attributed to the buried disulfide-linked 3D nanostructure of the ReSi nanoshell, optimized at an appropriate thickness, enabling not only buffering of small redox disturbances in the extracellular milieu but also the satisfied sensitivity for rapid redox sensing. Such a ReSi-functionalized gold nanoparticle-based nanoconjugate possesses the potential to serve as an effective intracellular drug carrier for future cancer theranostics.     

In situ intramolecular difluorocarbene-triggered synthesis of 2-gem-difluoro-2,3-dihydrobenzofuran-3-ols

Herein we report an unprecedented reaction between substituted salicylaldehydes and SCDA to furnish 2,2-difluoro-2,3-dihydrobenzofuran-3-ols. The reaction is highly effective for a range of diverse salicylaldehydes bearing meta-electron-withdrawing substituents. Of particular interest was the discovery that the requirement for a base in the occurred reaction directly correlated with the pKa of the substrates used.