- Corrosion inhibition of magnesium alloy in NaCl solution by ionic liquid: Synthesis, electrochemical and theoretical studies
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A new ionic liquid, benzyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([BPP][NTf2]), for magnesium alloy is synthesized. The potential of [BPP][NTf2] to be inhibitor is firstly estimated as compared with [P6,6,6,14][NTf2] by theoretical calculations. Then, the inhibition of AZ31B Mg alloy in 0.05 wt% NaCl solution is evaluated by [BPP][NTf2] is investigated by Tafel linear polarization method, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The most optimum inhibitor efficiency of [BPP][NTf2] is 91.4% at room temperature. The adsorption of [BPP][NTf2] on the surface of AZ31B Mg alloy obeys Langmuir isotherm with predominantly chemical adsorption. The corresponding result is further analyzed by the theory. The corrosive product is detected by Fourier transform infrared spectrum (FTIR). The possible inhibition mechanism is proposed, in which the effect of cation on inhibition is proposed in addition to the influence of anion.
- Su, Huishuang,Liu, Yue,Gao, Xing,Qian, Yafeng,Li, Weijie,Ren, Tiegang,Wang, Li,Zhang, Jinglai
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- Arylmethyloxyphenyl derivatives: Small molecules displaying P-glycoprotein inhibition
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Some arylmethyloxyphenyl derivatives were prepared as simplified structures of analogous arylpiperazines with high affinity toward dopaminergic D 2 and serotonergic 5-HT1A receptors and inhibiting P-glycoprotein (P-gp). The compounds 5b and 8b displayed good P-gp inhibition activity measured as [3H]vinblastine transport inhibition in the Caco-2 cell monolayer and intracellular doxorubicin accumulation in MCF7/Adr cells by flow cytometry. Compounds 5b and 8b also inhibited, dose-dependently, ATP-ase activation induced by P-gp substrate vinblastine.
- Colabufo, Nicola Antonio,Berardi, Francesco,Perrone, Roberto,Rapposelli, Simona,Digiacomo, Maria,Balsamo, Aldo
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- Preparation of fat-liquor based on jojoba oil under phase transfer catalysis
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Jojoba oil is of immense importance for industrial applications. There are a lot of published articles concerning its various uses in cosmetics, detergents, surfactants and lubricants. Therefore, this work was devoted to exploring its application for further use in the leather industry as a fat-liquoring agent. The fat-liquoring process is one important step in leather manufacturing, with the intention of obtaining leather of full, soft handle, flexibility, and pliability as well as improving its mechanical properties. The study involved preparation of jojoba fat-liquor via a sulfitation process. An improvement of the sulfitation process based on combined SO3 content was achieved under phase transfer catalysis (PTC). Two differently prepared types of phase transfer catalyst of phosphonium and ammonium types were investigated, namely, benzyl tri-phenyl phosphonium chloride (BTPP) and tri-ethyl benzyl ammonium chloride (TEBA). The fat-liquored leather led to an improvement in its mechanical properties such as tensile strength and elongation at break. In addition, a significant enhancement of the texture of the treated leather by jojoba fat-liquor as indicated in the scanning electron microscope (SEM) images was observed.
- Nashy, El-Shahat H. A.,Megahed,Abd El-Ghaffar
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- THERAPY
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The invention addresses radioresistance in cancer treatment involving radiotherapy and, in particular, limitations associated with the use of the drug sulfasalazine. Specifically, it provides a series of compounds for use as radiosensitizers in the treatment of cancers such as glioblastomas which are lethal and inherently resistant to radiotherapy, in one embodiment, the invention provides compounds of general formula (I), their stereoisomers and pharmaceutically acceptable salts for use as radiosensitizers in the treatment of cancer wherein ring A is selected from optionally substituted phenyl, biphenyl and fluorenyl; each X is independently selected from: -C1-6 alkyl (preferably C1-3 alkyl, e.g. -CH3), -O-C1-6 alkyl (preferably -O-C1-3 alkyl, e.g, -OCH3), -S-C1-6 alkyl (preferably -S-C1-3 alkyl, e.g, -SCH3), -OH, -SH, -CO2R1 (where R1 is H or C1-6 alkyl, preferably C1-3 alkyl, e.g. -CH3), -SO2-C1-6 alkyl (preferably -SO2-C1-3 alkyl, e.g. -SO2-CH3), -SO2-NR2R3 (where R2 is H and R3 is optionally substituted phenyl), -NR4R5 (wherein R4 and R5 are independently selected from H, C1-6 alkyl (preferably C1-3 alkyl, e.g. -CH3), and -CO-C1-6 alkyl (preferably -CO-C1-3 alkyl, e.g. -CO-CH3), halogen (e.g. F, Cl or Br), and optionally substituted tetrazolyl; n is an integer from 0 to 5, preferably 0 to 2, e.g. 1 or 2; and denotes an E or Z double bond.
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(2021/04/02)
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- Structure-Activity-Relationship-Aided Design and Synthesis of xCT Antiporter Inhibitors
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The xCT antiporter is a cell membrane protein involved in active counter-transportation of glutamate (outflux) with cystine (influx) over the human cell membrane. This feature makes the xCT antiporter a crucial element of the biosynthesis of the vital free radical scavenger glutathione. The prodrug sulfasalazine, a medication for the treatment of ulcerative colitis, was previously proven to inhibit the xCT antiporter. Starting from sulfasalazine, a molecular scaffold jumping followed by SAR-assisted design and synthesis provided a series of styryl hydroxy-benzoic acid analogues that were biologically tested in vitro for their ability to decrease intracellular glutathione levels using four different cancer cell lines: A172 (glioma), A375 (melanoma), U87 (glioma) and MCF7 (breast carcinoma). Depletion of glutathione levels varied among the compounds as well as among the cell lines. Flow cytometry using propidium iodide and the annexin V marker demonstrated minimal toxicity in normal human astrocytes for a promising candidate molecule (E)-5-(2-([1,1′-biphenyl]-4-yl)vinyl)-2-hydroxybenzoic acid.
- Cirillo, Davide,Sarowar, Shahin,?yvind Enger, Per,Bj?rsvik, Hans-René
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p. 2650 - 2668
(2021/06/01)
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- Chiral Imidodiphosphoric Acid-Catalyzed Highly Diastereo- and Enantioselective Synthesis of Poly-Substituted 3,4-Dihydro-2 H-pyrans: [4 + 2] Cycloadditions of β,γ-Unsaturated α-Ketoesters and 3-Vinylindoles
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Imidodiphosphoric acids were employed to catalyze inverse-electron-demand hetero-Diels-Alder reaction of β,γ-unsaturated α-ketoesters and 3-vinylindoles. A series of optically active 3,4-dihydro-2H-pyran derivatives with three contiguous stereogenic centers was synthesized in excellent yields (70-99%), diastereoselectivities (>20:1), and enantioselectivities (73-99%). The resulting indole containing 3,4-dihydro-2H-pyran could be converted to tetrahydropyran derivatives, which appear in several biological active compounds by simple hydrogenation reduction.
- Guan, Xu-Kai,Liu, Guo-Feng,An, Dong,Zhang, Heng,Zhang, Suo-Qin
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supporting information
p. 5438 - 5442
(2019/08/01)
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- Long sought synthesis of quaternary phosphonium salts from phosphine oxides: Inverse reactivity approach
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Quaternary phosphonium salts (QPS), a key class of organophosphorus compounds, have previously only been available by routes involving nucleophilic phosphorus. We report the realisation of the opposite approach to QPS utilising phosphine oxides as the electrophilic partner and Grignard reagents as nucleophiles. The process is enabled through the crucial intermediacy of the derived halophosphonium salts. The route does not suffer from the slow kinetics and limited availability of many parent phosphines and a broad range of QPS were prepared in excellent yields.
- Vetter, Anna C.,Nikitin, Kirill,Gilheany, Declan G.
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p. 5843 - 5846
(2018/06/13)
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- Synthesis of aryl and heterocyclic polyenes and their activity in free radical scavenging
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Aryl polyenes and heterocyclic polyenes with the same central C20 unit of β,β-carotene but different terminal groups were synthesised. Their free radical scavenging activity was measured by a 1,1-diphenyl-2-picrylhydrazinyl spectrophotometric method. The results indicated that all the new compounds have free radical scavenging activity.
- Deng, Kaini,Yang, Zuxing,Luo, Juan,Wu, Kaiqun
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p. 129 - 132
(2018/04/20)
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- Ionic Liquids as Solvents for SN2 Processes. Demonstration of the Complex Interplay of Interactions Resulting in the Observed Solvent Effects
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Bimolecular nucleophilic substitution reactions between triphenylphosphine and benzylic electrophiles have been examined in an ionic liquid to probe interactions with species along the reaction coordinate. Trends in the rate constant were found on both varying the leaving group and the electronic nature of the aromatic ring. In all the cases considered, interactions between the components of the ionic liquid and the transition state were shown to be more significant in determining reaction outcome than previously observed for this class of reaction. This demonstrates the importance of considering interactions of the ionic liquid components with all species along the reaction coordinate when investigating the origin of ionic liquid solvent effects, along with how such effects might be exploited.
- Schaffarczyk McHale, Karin S.,Haines, Ronald S.,Harper, Jason B.
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p. 1162 - 1168
(2019/01/04)
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- Benzofuran compound and its preparation, use (by machine translation)
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The invention relates to a benzofuran compound and its preparation, use, its structural formula such as formula (I) as shown: Wherein R1 , R2 , R4 Are selected from hydrogen, C1 - C5 Alkyl, nitro, halogen, ester, hydroxy, amino, amide base or alkoxyl; R3 Hydrogen, C1 - C5 Alkyl, benzyl, aromatic or heteroaromatic group. The invention also relates to the benzofuran compounds in inhibiting the application of gram-positive to be used repeatedly. The invention relates to 3 - oxime substituted benzene and furan structure aromatic ring as the center, the establishment and optimize the preparation method of the compound, and on the preparation of novel compound of the bacteriostatic screening experiment, through initial bacteriostatic test to confirm that preparation compound has broad-spectrum bacteriostatic activity. (by machine translation)
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Paragraph 0057-0058
(2017/08/18)
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- One-pot synthesis of 2,4,5-trisubstituted imidazole derivatives catalyzed by BTPPC under solvent-free conditions
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A simple and efficient method for one-pot synthesis of lophine derivatives (2,4,5-trisubstituted imidazoles) by using the benzyltriphenylphosphonium chloride (BTPPC), as a catalyst, under solvent-free conditions is described. BTPPC is an available and inexpensive catalyst; also, it can be easily supplied. This procedure led to the corresponding 2,4,5-trisubstituted imidazoles products in high yields.
- Alikarami, Mohammad,Amozad, Mozhgan
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p. 177 - 184
(2017/07/24)
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- Synthesis and antimicrobial evaluation of 3-substituted-imine-6-hydroxy-benzofuran derivatives
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A series of 3-substituted-imine-6-hydroxy-benzofuran derivatives were chemically synthesized and biologically evaluated as antibacterial and antifungal agents against Candida albicans, Escherichia coli, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Bacillus subtilis. Most compounds showed a selective antibacterial activity to gram-positive bacteria and four compounds revealed great antibacterial activities against methicillin-resistant Staphylococcus aureus comparing to the positive control (Ceftazidime) with MIC80 = 12.5–25 μg/mL. Structure-activity relationship studies demonstrated that the free hydroxy group at the C-6 position is essential to the antibacterial activity, and the aromatic imine fragment at the C-3 position also greatly increases antibacterial activity.
- He, Wan,Xu, Buzhe,Bao, Jian,Deng, Xinxian,Liu, Wenlu,Zhang, Yong,Jiang, Faqin,Fu, Lei
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p. 2485 - 2497
(2016/10/25)
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- Synthesis and tyrosinase inhibition activity of trans-stilbene derivatives
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Synthesis of a focussed library of trans-stilbene compounds through Wittig and other base catalysed condensation reactions is presented. The synthesized stilbenes were screened for their inhibitory potential against murine tyrosinase activity to explore the structure activity relationship (SAR). Presence of electron withdrawing group (-CN) at the double bond and hydroxyl group or halogen atom especially at para-position on the aromatic rings was found to significantly elevate the inhibitory activity. Among all the compounds screened, compounds 2, 6, 8, 10, 11, 15 and 21 were found to exhibit appreciable inhibitory activity. Compound 21 ((E)-2,3-bis(4-Hydroxyphenyl)acryonitrile) was found to be the most active with an IC50 value of 5.06 μM which is less than half of the value 10.78 μM observed for resveratrol (common standard used in murine tyrosinase activity studies) under similar conditions. The results obtained from the present study reveal structural/functional group sensitivity for the tyrosinase inhibitory activity of stilbenoid moieties and are expected to be very helpful for the design and synthesis of novel, selective and effective tyrosinase inhibitors.
- Ismail, Tabasum,Shafi, Syed,Srinivas, Jada,Sarkar, Dhiman,Qurishi, Yasrib,Khazir, Jabeena,Alam, Mohammad Sarwar,Kumar, Halmuthur Mahabalarao Sampath
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- Nitrogen: Versus phosphorus nucleophiles-how changing the nucleophilic heteroatom affects ionic liquid solvent effects in bimolecular nucleophilic substitution processes
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A series of nitrogen and phosphorus nucleophiles have been investigated to determine whether the previously established ionic liquid solvent effects on a bimolecular nucleophilic substitution (SN2) reaction vary with the nature of the nucleophilic centre. Reaction of group 15 triphenyl nucleophiles with benzyl bromide showed a different trend in the rate constant with increasing proportions of ionic liquid in the reaction mixture than was observed with pyridine. This result suggests additional interactions are important; a supposition supported by differences in reaction outcome observed when the electrophile was varied in reactions with triphenylphosphine. A novel ionic liquid solvent effect was observed in the reaction of tributylamine with benzyl bromide, with the position of equilibrium varying with the proportions of the ionic liquid present in the reaction mixture. Overall, the work presented demonstrates the importance of considering all possible interactions between an ionic liquid solvent and species along the reaction coordinate and has expanded upon our current predictive framework for ionic liquid solvent effects. Such understanding is important as it allows further development of a predictive framework for the application of ionic liquids in preparative chemistry.
- Schaffarczyk McHale, Karin S.,Hawker, Rebecca R.,Harper, Jason B.
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supporting information
p. 7437 - 7444
(2016/09/12)
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- A hierarchical porous ionic organic polymer as a new platform for heterogeneous phase transfer catalysis
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In this work we demonstrate for the first time the construction of a hierarchical porous ionic organic polymer via the polymerization of the vinyl-functionalized quaternary phosphonium salt monomer under solvothermal conditions. The resultant polymerized quaternary phosphonium (PQP) salt features a hierarchical porous structure and excellent amphiphilicity. After anion-exchange with peroxotungstate, the afforded W2O11/PQP demonstrates excellent performances as a heterogeneous phase-transfer catalyst in the context of epoxidation of olefin and oxidation of dibenzothiophene when using the environmentally benign H2O2 as the oxidant, superior to the homogeneous counterparts and other types of phase-transfer catalysts. Our work thereby paves a way to advance hierarchical porous ionic organic polymers as a new type of platform for heterogeneous phase transfer catalysis.
- Sun, Qi,Ma, Shengqian,Dai, Zhifeng,Meng, Xiangju,Xiao, Feng-Shou
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p. 23871 - 23875
(2016/01/15)
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- Synthesis and biological evaluation of resveratrol-coumarin hybrid compounds as potential antitumor agents
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Eighteen resveratrol-coumarin hybrid compounds (6 or 7-styryl-3- phenylcoumarin) were designed, synthesized and thirteen compounds were evaluated for their antitumor activities against MCF-7, HCT-28, and K562 tumor cell lines. Among them, compounds 2Z, 2E, 5E, and 7E showed varying degrees of growth inhibition of the above cell lines (IC50: 3.78-19.16 μmol/L). On the basis of the biological results, structure-activity relationships were obtained and discussed.
- Shen, Wei,Mao, Jianfeng,Sun, Juan,Sun, Minjie,Zhang, Can
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p. 1630 - 1640
(2013/07/26)
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- Tuning the nature of the fluorescent state: A substituted polycondensed dye as a case study
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An extensive spectroscopic analysis is presented of an elongated polycondensed dye with a donor-acceptor substitution. The charge-transfer (CT) state, polarized along the long molecular axis, is close in energy to a local excitation (LE) of the polycondensed system, roughly polarized along the short molecular axis, which makes this system particularly suitable to investigate the subtle LE/CT interplay. An essential-state model is presented that quantitatively reproduces absorption and fluorescence spectra, as well as fluorescence emission and excitation anisotropy spectra collected in solvents of different polarity and viscosity, which sets a sound basis for the understanding of how solvent polarity and solvent relaxation affect the nature of low-lying excitations. The markedly different fluorescence emission and excitation anisotropy spectra measured in glassy and liquid polar solvents unambiguously demonstrate the major role played by solvent relaxation in the definition of fluorescence properties of the dye. Charge-transfer or local excitations? Fluorescence emission from a substituted azachrysene chromophore is shown to change its nature according to solvent polarity. The different polarization of the low-energy local and charge-transfer excitations (see scheme) is responsible for highly informative fluorescence anisotropy spectra. Experimental results are interpreted and reproduced based on an original three-state model. Copyright
- Sissa, Cristina,Calabrese, Valentina,Cavazzini, Marco,Grisanti, Luca,Terenziani, Francesca,Quici, Silvio,Painelli, Anna
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p. 924 - 935
(2013/02/23)
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- Synthesis and study of fluorescent properties of benzothiazolylthieno- thiophene derivatives
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A number of benzothiazolylthienothiophenes have been synthesized. Spectral studies have revealed that all these compounds have fluorescent properties that depend on their structure. Dependence of absorption and fluorescence bands positions on the nature of substituents have been established. Increase of the electron-withdrawing nature of substituents led to bathochromic shift of the absorption and fluorescence bands as well as to decrease of the fluorescence intensity.
- Zavarzin,Karabaeva,Shimkina,Shorunov,Yarovenko,Platonova,Kobeleva,Valova,Barachevskii,Krayushkin
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p. 1445 - 1452
(2014/07/21)
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- Experimental and theoretical studies on the one-photon and two-photon properties of a series of carbazole derivatives containing styrene
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Symmetric-type carbazole derivatives show great potential for application in two-photon absorption (TPA) materials and organic light-emitting diodes. The absorption spectra and fluorescence emission spectra of three different N-alkyl symmetric-type carbazole derivatives were investigated. The density functional theory (DFT) time-dependent-DFT//Becke, three-parameter, Lee-Yang-Parr/6- 31G* method has been used to theoretically study one-photon absorption properties. The computational results are in good agreement with the available experimental values. The two-photon excited fluorescence of the compounds was surveyed by 120fs pulse at 790nm Ti: sapphire laser operating at 1kHz repetition rate. Two-photon excited fluorescence was obtained in the range of 380-600nm, and TPA cross-sections were calculated. The TPA properties of the series of compounds were investigated by the ZINDO/single and double electronic excitation configuration interaction method. The influence of the chemical structure of the compounds on two-photon optical properties was discussed. The results show how the different changes in one-photon absorption and TPA properties on the basis of lengthening the conjugated bridge and the different carbazole N-alkyl substituents are attributed to the transition dipole moment in the excited process. Copyright
- Li, Liang,Wu, Yiqun,Zhou, Qinling,He, Chunying
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experimental part
p. 362 - 372
(2012/07/28)
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- Synthesis, characterization, X-ray structural analysis, and iodination ability of benzyl(triphenyl)phosphonium dichloroiodate
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Benzyl(triphenyl)phosphonium dichloroiodate (BTPPICl2), BnPh3P+(ICl2)-, is easily synthesized in a nearly quantitative yield by the addition of BnPh 3P+Cl- to a CH2Cl2 solution of iodine monochloride (ICl). BnPh3P+Cl - can be prepared by the reaction of Ph3P and BnCl. The compound was characterized by physicochemical and spectroscopic methods (elemental analysis, FT-IR, and 1H-NMR). The use of phosphonium counterion improves the quality of the BTPPICl2 crystals. BTPPICl2 crystallizes in the monoclinic system, and its crystal and molecular structure has been determined at 100(1) K by X-ray diffraction. The structure was solved by the direct method and had refined R value of 0.0637 for 699 reflections (I>2σ(I)), space group P21/n with a=12.4700(3), b=13.2196(3), c=14.4580(3) A, β=102.6340(10)°, V=2325.67(9) A3, and Z=4. The I-atom is coordinated by two Cl-atoms as ligands in a linear geometry. This compound is a versatile reagent for the efficient and selective iodination of organic substrates, in particular of aromatic phenols to the corresponding iodo compounds, under mild conditions. To assess the generality of method, a wide variety of phenols with electron-donating and electron-withdrawing substituents were studied. BTPPICl2 is a mild iodination reagent, which offers a new avenue for an expeditious iodination of phenols. The inexpensive, relatively non-toxic reagent, and mild conditions are the positive features of the procedure and reagent. Copyright
- Imanieh, Hossein,Ghammamy, Shahriar,Nikje, Mir Mohammad Alavi,Hosseini, Farhang,Aghbolagh, Zahra Shokri,Fun, Hoong-Kun,Khavasi, Hamid Reza,Kia, Reza
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experimental part
p. 2248 - 2255
(2012/01/12)
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- Sintered silicon carbide: A new ceramic vessel material for microwave chemistry in single-mode reactors
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Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single-mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high-temperature fluorine-chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors. Simulating conductive heat transfer in a microwave: Using reaction vials made out of strongly microwave-absorbing silicon carbide (SiC) in a microwave reactor simulates a conductively heated autoclave experiment due to efficient shielding of the electromagnetic field by the SiC vial. Advantages of SiC vials for microwave processing include their excellent corrosion resistance, thermal stability, and high thermal effusivity and conductivity.
- Gutmann, Bernhard,Obermayer, David,Reichart, Benedikt,Prekodravac, Bojana,Irfan, Muhammad,Kremsner, Jennifer M.,Kappe, C. Oliver
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supporting information; experimental part
p. 12182 - 12194
(2011/02/23)
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- Pentiptycene-derived light-driven molecular brakes: Substituent effects of the brake component
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Five pentiptycene-derived stilbene systems (1R; R = H, OM, NO, Pr, and Bu) have been prepared and investigated as light-driven molecular brakes that have different-sized brake components (1Hrot = 108-109 s-1) with little interaction with the brake component in the trans form ((E)-1R), which corresponds to the brake-off state. When the brake is turned on by photoisomerization to the cis form ((Z)-1R), the pentiptycene rotation can be arrested on the NMR spectroscopic timescale at temperatures that depend on the brake component. In the cases of (Z)-1NO, (Z)-1Pr, and (Z)-1Bu, the rotation is nearly blocked (krot = 2-6 s-1) at 298 K. It is also demonstrated that the rotation is slower in [D6]DMSO than in CD2Cl 2. A linear relationship between the free energies of the rotational barrier and the steric parameter A values is present only for (Z)-1H, (Z)-1OM, and (Z)-1NO, and it levels off on going from (Z)-1NO to (Z)-1Pr and (Z)-1Bu. DFT calculations provide insights into the substituent effects in the rotational ground and transition states. The molar reversibility of the E-Z photoswitching is up to 46%, and both the E and Z isomers are stable under the irradiation conditions.
- Sun, Wei-Ting,Huang, Yau-Ting,Huang, Guan-Jhih,Lu, Hsiu-Feng,Chao, Ito,Huang, Shou-Ling,Huang, Shing-Jong,Lin, Ying-Chih,Ho, Jinn-Hsuan,Yang, Jye-Shane
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experimental part
p. 11594 - 11604
(2010/12/18)
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- Aluminium triflate catalysed cyclisation of unsaturated alcohols: novel synthesis of rose oxide and analogues
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Aluminium trifluoromethanesulfonate was used as an efficient catalyst for the cycloisomerisation of several unsaturated alcohols into cyclic ethers such as rose oxide and some of its ether analogues.
- Coulombel, Lydie,Weiwer, Michel,Dunach, Elisabet
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experimental part
p. 5788 - 5795
(2010/03/03)
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- Microwave chemistry in silicon carbide reaction vials: Separating thermal from nonthermal effects
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Running oil-bath chemistry in a microwave! Using reaction vials made out of strongly microwave-absorbing silicon carbide (SiC) in a microwave reactor simulates experiments conducted in an autoclave with conductive heating because of the efficient shielding of the electromagnetic field by the SiC vial. This technology makes it possible to study the significance of microwave effects.
- Obermayer, David,Gutmann, Bernhard,Oliver Kappe
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supporting information; scheme or table
p. 8321 - 8324
(2010/01/06)
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- Nonthermal microwave effects revisited: On the importance of internal temperature monitoring and agitation in microwave chemistry
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(Graph Presented) The concept of nonthermal microwave effects has received considerable attention in recent years and is the subject of intense debate in the scientific community. Nonthermal microwave effects have been postulated to result from a direct stabilizing interaction of the electric field with specific (polar) molecules in the reaction medium that is not related to a macroscopic temperature effect. In order to probe the existence of nonthermal microwave effects, four synthetic transformations (Diels-Alder cycloaddition, alkylation of triphenylphosphine and 1,2,4-triazole, direct amide bond formation) were reevaluated under both microwave dielectric heating and conventional thermal heating. In all four cases, previous studies have claimed the existence of nonthermal microwave effects in these reactions. Experimentally, significant differences in conversion and/or product distribution comparing the conventionally and microwave-heated experiments performed at the same measured reaction temperature were found. The current reevaluation of these reactions was performed in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using a multiple fiber-optic probe system. Using this technology, the importance of efficient stirring and internal temperature measurement in microwave-heated reactions was made evident. Inefficient agitation leads to temperature gradients within the reaction mixture due to field inhomogeneities in the microwave cavity. Using external infrared temperature sensors in some cases results in significant inaccuracies in the temperature measurement. Applying the fiber-optic probe temperature monitoring device, a critical reevaluation of all four reactions has provided no evidence for the existence of nonthermal microwave effects. Ensuring efficient agitation of the reaction mixture via magnetic stirring, no significant differences in terms of conversion and selectivity between experiments performed under microwave or - oil bath conditions at the same internally measured reaction temperatures were experienced. The observed effects were purely thermal and not related to the microwave field.
- Herrero, M. Antonia,Kremsner, Jennifer M.,Kappe, C. Oliver
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- Arylethenylbenzofuroxan derivatives as drugs for chagas disease: Multigram batch synthesis ysubg a wuttug#bideb process
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In the present work, we developed robust processes for the preparation of new antitrypanosomal benzofuroxans, E and Z isomers of 5-arylethenylbenzo[1,2-c] 1,2,5-oxadiazole p1N-oxide 1-6, in muhigram batch through Wittig-Boden conditions as the key synthetic step. In these conditions, the generation of the benzofurazans, as secondary byproduct, was minimized.
- Porcal, Williams,Merlino, Alicia,Boiani, Mariana,Gerpe, Alejandra,Gonzalez, Mercedes,Cerecetto, Hugo
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p. 156 - 162
(2013/01/03)
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- The design, synthesis, and anti-tumor mechanism study of N-phosphoryl amino acid modified resveratrol analogues
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A novel series of trans-N-phosphoryl amino acid modified resveratrol analogues were synthesized and evaluated in vitro for their cytotoxic effects against CNE-1 and CNE-2 cell lines. These analogues showed good anti-proliferative activity, among which 8d, 8e, 8j, and 9d displayed much stronger inhibition effect than resveratrol and 8d showed the most potent activity with IC50 value at 3.45 ± 0.82 μM. The anti-tumor effects of 8d, 8e, 8j, and 9d were due to the induction of apoptosis, confirmed by the DNA fragmentation and flow cytometry analysis using PI (propidium iodide) staining and Annexin-V-FITC/PI staining assay. The PI staining assay also showed that 8d, 8e, 8j, and 9d caused cell cycles arrest at G0-G1 phase which finally led to cell apoptosis. Further mechanism study on compound 8d against CNE-2 cells has shown the PARP cleavage, which is a hallmark of caspase-3 activation, as well as the activation of caspase-9, and the intracellular ROS generation. These results all suggest that 8d induced a mitochondrial-dependent apoptosis pathway.
- Liu, Huachen,Dong, Aijun,Gao, Chunmei,Tan, Chunyan,Liu, Hongxia,Zu, Xuyu,Jiang, Yuyang
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experimental part
p. 10013 - 10021
(2009/04/06)
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- Synthesis and structures of new conformationally rigid 1-aza-1,3-dienes of the acenaphthene series
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The Wittig reaction of 1-tert-butyliminoacenaphthen-2-one with benzylidenetriphenylphosphoranes produces new 1-aza-1,3-dienes of the acenaphthene series, which can bind butyllithium to the C=C bond of the enimine fragment C=C-C=N.
- Skatova,Fedushkin,Maslova,Hummert,Schumann
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p. 2284 - 2289
(2008/09/18)
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- Synthesis of phosphonium salts under microwave activation - Leaving group and phosphine substituents effects
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The specific nonpurely thermal effects of microwaves were evidenced according to neutral or charged leaving groups during nucleophilic substitution of benzylic electrophiles with triphenylphosphine and tributylphosphine. Microwave (MW) irradiation considerably enhanced the reactions with charged alkylating agents, especially under solvent-free conditions. Results are interpreted considering the magnitude of MW effects according to the position of the transition state along the reaction coordinates.
- Cvengros, Jan,Toma, Stefan,Marque, Sylvain,Loupy, Andre
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p. 1365 - 1371
(2007/10/03)
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- Experimental evidence for multiple oxidation pathways in the (salen)Mn-catalyzed epoxidation of alkenes
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The substrate electronic effects on the selectivity in the catalytic epoxidation of para-substituted cis stilbenes 2a-i were investigated by using (R,R)-[N,N′-bis(3,5-di-tBu-salicylidene)-1,2-cyclohexanediamine] manganese(III) chloride 1 in benzene as the catalyst with iodosobenzene as the terminal oxidant. A Hammett study of the selectivity results reveals a stronger electrophilic character than previously assumed in the (salen)Mn-catalyzed reaction. In general, the best correlations with the experimental values were obtained by using the Hammett σ+ values, which gave ρ = -1.37 for the rate of cisepoxide formation and ρ = -0.43 for the rate of the stepwise process leading to the corresponding trans product. The reaction involves two separate pathways as indicated also by the competitive breakdown of the intermediate on the path to trans epoxide for methoxy-substituted substrates. The asynchronicity in the concerted pathway leading to cis epoxide is apparent for 4-methoxy-4′-nitrostilbene, which yields cis epoxide with 75% ee entirely as a result of electronic effects.
- Linde, Christian,Koliai, Nordine,Norrby, Per-Ola,Akermark, Bjoern
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p. 2568 - 2573
(2007/10/03)
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- Ylidylphosphanes and -diphosphanes
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Chlorophosphanyl and dichlorophosphanyl alkylidene- and benzylidenephosphoranes 6 and 8 are converted by reaction with LiAlH4 to the respective phosphanes 7 and 9. The former can be isolated, but decompose on heating or on protonation to give the ylidyl diphosphane 11 and the phosphonium ylide or phosphonium salt, respectively. The final products are the cyclooligophosphanes 15-17. Only the C-tert-butyl derivative 7c is stable in both regards. The conformation of the RPH group in 7 as compared to that of the RPCl group in 6 clearly reflects their different interaction with the ylide moiety.
- Breitsameter, Florian,Schmidpeter, Alfred,Schier, Annette
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p. 381 - 388
(2007/10/03)
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- Stereoselective addition of diphenylphosphine to substituted diphenylethynes: Synthetic, NMR and X-ray crystallographic studies
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The base-catalysed addition of diphenylphosphine to the substituted diphenylethynes RC≡CR′ (R = Ph, R′ = Ph, o-tolyl, m-tolyl or 2-biphenyl; R = m-tolyl, R′ = o-tolyl or m-tolyl) yielded Ph2PC(R)=CHR′ and/or Ph2PCH(R)CH(R′)PPh2. Proton, 13C, 13P and two-dimensional rotating frame Overhauser enhancement 1H NMR spectra have been used to determine the stereochemical pathways of the reactions and the stereochemistry of the products. In general the more hindered alkynes undergo monoaddition ultimately to yield phosphinoalkenes with the Ph2P attached to the carbon bearing the least bulky substituent and cis to the olefinic proton, while for the less hindered alkynes the trans isomer is formed initially and this then reacts further to give mesolerythro-diphosphinoalkanes. Bis(o-tolyl)ethyne does not react with Ph2PH under the same conditions. Crystal structures were determined for E- and Z-Ph2P(Ph)C=CHPh and show distortions of interbond angles consistent with the pattern of strain implied by the foregoing reactions. The sulfides of the phosphinoalkenes and the Mo(CO)4 complexes of the diphosphinoalkanes were also prepared and their 1H, 13C and 31P NMR spectra recorded. In several cases the pattern of 13CO NMR signals for the complexes was used unambiguously to determine the stereochemistry of the parent diphosphines.
- Bookham, Jonathan L.,Smithies, Darren M.,Wright, Anna,Thornton-Pett, Mark,McFarlane, William
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p. 811 - 818
(2007/10/03)
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- Synthesis of C-glycosyl isoxazoles and branched-chain enuloses from 2,3-O-isopropylidene-D-glyceraldehyde
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The synthesis of 5-glycosyl isoxazoles with 3-alkyl-, 3-aryl, 3,4-dialkyl, 3-aryl-4-alkyl or 3-alkyl-4-bromo substituents is reported. Deoxyenuloses were obtained from reaction of 2,3-O-isopropylidene-D-glyceraldehyde and several phosphorus ylides, which contain a carbonyl group, by a Wittig reaction. C-glycosyl α,β-unsaturated ketones were obtained, with the polyhydroxylate chain lengthened by two or three carbon atoms. In the second phase the ketones were transformed into the corresponding C-glycosyl α,β-unsaturated ketoximes, leading to the C-glycosyl isoxazoles, which were converted into the title compounds via removal of the isopropylidene group of suitably protected carbohydrates. The solubility of the synthetized C-glycosyl isoxazoles were modified by free hydroxyl groups in such a way that their behaviour against certain viruses and their potential antiviral activity could be studied.
- Bá?ez Sanz,López Sastre,Pati?o Molina,Romero-ávila García
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p. 1331 - 1350
(2007/10/03)
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- Syntheses of 2-(2-arylethyl)-1-methylimidazoles
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2-(2-Arylethyl)-1-methylimidazoles 3 could be prepared by different methods. The best method was the Wittig reaction of aryltriphenylphosphonium chloride 8 with 2-formyl-1-methylimidazole to give compound 6. Reduction of compound 6 with Raney nickel gave compound 3.
- Shafiee,Morteza-Semnani,Foroumadi
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p. 671 - 673
(2007/10/03)
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- Third generation antitumor platinum(II) complexes of the [1-(fluoro/difluorophenyl)-2-phenylethylenediamine]platinum(II) type
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The diastereomeric 1-(fluoro/difluorophenyl)-2-phenylethylenediamines (4-fluoro: erythro-1/threo-1; 2,4-difluoro: erythro-2/threo-2; 2,6-difluoro: erythro-3/threo-3) and the diastereomeric 1-(4-fluorophenyl)-2-(3-hydroxyphenyl)ethylenediamines (erythro-4/-threo-4) were synthesized from appropriately substituted stilbenes by reaction with IN3 and subsequent LiAlH4 reduction. Coordination of the 1,2-diphenylethylenediamines to platinum was carried out by use of K2PtI4. The water-soluble aquasulfatoplatinum(II) complexes (erythro/threo-1-PtSO4-erythro/threo-4-PtSO4) were obtained from the diiodoplatinum(II) complexes by reaction with Ag2SO4. Additionally erythro/threo-1-PtSO4 and erythro/threo-4-PtSO4 were transformed into the dichloroplatinum(II) complexes (erythro/threo-1-PtCl2, erythro/threo-4-PtCl2) by treatment with KCl. In contrast to the less effective erythro-configurated sulfatoplatinum(II) complexes the threoanalogues showed comparable or even superior activities to cisplatin on the human MDA-MB-231 breast cancer cell line. On the MXT-M-3.2 breast cancer of the mouse only erythro- and threo-4-PtSO4 caused similar effects like cisplatin. The strong inhibitory effect of the diastereomeric sulfatoplatinum(II) complexes on the P-388 leukemia of the mouse was equal to that of cisplatin. On the latter tumor threo-4-PtCl2 was the most active among the less toxic dichloroplatinum(II) derivatives.
- Gust,Schonenberger
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p. 595 - 603
(2007/10/03)
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- Photolysis of (Arylmethyl)triphenylphosphonium Salts. Substituent, Counterion, and Solvent Effects on Reaction Products
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Quaternary (arylmethyl)phosphonium salts of the general formula ArCH2-PR3(+)Y(-) (Ar = substituted phenyl or 1-naphthyl; R = phenyl, ferrocenyl, or butyl; Y(-) = BF4(-) or halide) have been photolyzed in acetonitrile or in methanol.Photolysis involved the cleavage of the P-CH2 bond and the products derived from both, the arylmethyl radical and the carbocation, were formed.The proportion of the radical- and carbocation-derived products was determined as a function of substituents in group Ar, of groups R, counterions Y(-), and the solvent.For the nonoxidizable counterion (BF4(-), the proposed mechanism of the reaction involves initial homolysis, followed by the escape of the radical products from a solvent cage, or by the electron transfer from carbon to phosphorus, yielding the corresponding arylmethyl carbocation.The latter can either react with the solvent to form the observed carbocation-derived product or can undergo recombination with the tertiary phosphine formed to yield the starting phosphonium ion.Some indication of the "inverted substituent effect" resulting from the inhibition of single electron transfer from an easily oxidized radical was obtained.For the oxidizable counterions (halides), an additional pathway is suggested, that involves electron transfer from the anion, yielding the arylmethyl radical and the phosphine, thus decreasing the ionic/radical products ratio.
- Imrie, C.,Modro, T. A.,Rohwer, E. R.,Wagener, C. C. P.
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p. 5643 - 5649
(2007/10/02)
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- The Effect of Electron-Donating and Electron-Withdrawing Substituents on 1H- and 13C-NMR Chemical Shifts of Novel 7'-Aryl-Substituted 7'-Apo-β-carotenes
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The synthesis of 7'-aryl-7'-apo-β-carotenes, where aryl (Ar) is Ph, 4-NO2C6H4, 4-MeOC6H4, 4-(MeO2C)C6H4, C6F5, and 2,4,6-Me3C6H2, is described.NMR Chemical shifts of all H- and C-atoms are presented, together with specific examples of the spectra.In contrast to 1H chemical shifts which, except for H-C(8') and H-C(7'), did not differ greatly from those of β,β-carotene, considerable variations in 13C chemical shifts were observed.Signals of the C(α) atoms of the polyene chain nAr were shielded, those of the C(β) atoms were deshielded, with some exceptions when n = 1; the effects decreased with increasing n.
- Hand, Elli S.,Belmore, Kenneth A.,Kispert, Lowell D.
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p. 1928 - 1938
(2007/10/02)
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- Electron Demand in the Transition State of the Cyclopropylidene to Allene Ring Opening
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The electronic structure of the transition state for the cyclopropylidene to allene conversion has been probed.The methodology involved the relative rates of ring opening vs trapping by MeOH for a series of variously substituted 2,3-diarylcyclopropylidenes.With the assumption that the rate of trapping was unaffected by substituents, a Hammett correlation was constructed.The negative value (-0.72) for ρ indicated that the carbenic center attracts electron density in the ring-opening transition state, much like the cyclopropyl cation to allyl cation transition state.Temperature-dependent studies showed that the observed preference for ring opening was driven by entropy factors.Also, using reasonable estimates for the close to diffusion-controlled trapping activation enthalpies, the derived enthalpies for ring opening were in close agreement with the best theoretical values.
- Warner, Philip,Sutherland, Robert
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p. 6294 - 6300
(2007/10/02)
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- (α-Haloalkyl)phosphonium Salts and Sulfur Nucleophiles: A New Type of Reaction Mechanism
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Reaction between (α-haloalkyl)phosphonium salts and some sulfur nucleophiles leads to the substitution product Ph3P+CH2SRX-.Evidence is presented that this substitution is not a normal SN2 reaction and that it occurs through formation of a phosphonium ylide and a disulfide, reaction between them, and action of the resulting salt on the starting phosphonium salt.Then RSX and Ph3=CH2 reenter the sequence, giving rise to a three-step chain nucleophilic substitution.
- Galli, Remo
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p. 5349 - 5356
(2007/10/02)
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- Studies on Organic Fluorine Compounds. XLII. Synthesis and Reactions of Phenyltrifluoromethylacetylenes
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Phenyltrifluoromethylacetylene (4a) was synthesized by the pyrolysis of triphenylphosphonium α-(trifluoroacetyl)benzylide (3a), which was easily derived from benzyl halide (1a).This method can be used for the synthesis of 4-substituted-phenyltrifluoromethylacetylenes (4).The 1,3-dipolar reaction of 4 with diazomethane and phenyl azide proceeds readily to give trifluoromethylated pyrazoles and triazoles.Keywords - trifluoromethyl; acetylene; 1,3-dipolar reaction; intramolecular Wittig reaction; trifluoroacetylphosphonium ylide; pyrazole; diazomethane; phenyl azide
- Kobayashi, Yoshiro,Yamashita, Toshinori,Takahashi, Katsuhiro,Kuroda, Hisashi,Kumadaki, Itsumaro
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p. 4402 - 4409
(2007/10/02)
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- SOLVENT EFFECTS ON KINETICS AND REACTION MECHANISMS. THE FORMATION OF PHOSPHONIUM SALT FROM BENZYL CHLORIDE AND TRIPHENYLPHOSPHINE
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Second-order rate constants and activation parameters for the reaction of benzyl chloride and triphenylphosphine have been measured in 18 protic and aprotic solvents covering a wide range of dielectric constant.The analysis of the medium effects by the more usual multiparameter approaches indicated that polarity and electrophilicity of the solvents are responsible for the observed reactivity.Solvation enthalpies and entropies of the reagents were also measured in some solvents in order to dissect the initial-state and transition-state contributions.
- Maccarone, Emanuele,Perrini, Giancarlo,Torre, Michele
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- 1H-NMR- AND MOESSBAUER INVESTIGATIONS ON THE ION PAIRS OF TETRACHLOROFERRATE(III) ANION WITH QUATERNARY PHOSPHONIUM CATIONS
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Paramagnetic ion pairs were investigated by 1H-NMR and Moessbauer spectroscopy in chloroform and dimethyl sulphoxide.It has been shown that the chemical shifts of 1H-NMR peaks arise from a combination of contact and pseudocontact interactions of opposite sign, and the ratio of interactions was definitely influenced by the extent of solvation.On the basis of Moessbauer measurements it was shown that the change of the cation size had an effect on the electron delocalization and symmetry conditions of iron(III) in solid samples, too.In concentrated frozen solutions of ion pairs, different interactions were indicated by Moessbauer spectros copy in chloroform and dimethyl sulphoxide, in accordance with 1H-NMR results.However, in dilute solution such an anion-solvent interaction was observed directly, which could be shown by the NMR method only indirectly.
- Vincze, L.,Papp, S.
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p. 153 - 162
(2007/10/02)
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- The Nucleophilic Reactivity of Organophosphorus Compounds. Part 4. The Alkylation of Phosphorus Acid Anions with 'Onium Keten Acetals
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The preparations of phosphonium and pyridinium keten acetals are reported and their reactions with a variety of phosphorus acid anions are described.The novel pyridinium keten acetals are useful reagents for the alkylation of various acid anions in aprotic, aqueous-emulsion media.
- Zaslona, Alexander T.,Hall, C. Dennis
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p. 3059 - 3064
(2007/10/02)
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- Synthesis and Photocylization of some 4-(5)Arylethenylimidazoles
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The synthesis of eleven 4-(5)arylethenylimidazoles and their separation into cis and trans isomers is described.Ir, uv, nmr, and mass spectrometric data of the compounds are given.The photocyclization of the unsubstituted and p-substituted compounds is reported.
- Lindberg, Gerd,Stensioe, Karl-Erland,Wahlberg, Kerstin
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p. 679 - 683
(2007/10/02)
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