- Synthesis and properties of novel polyimide fibers containing phosphorus groups in the main chain
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A series of polyamic acid copolymers (co-PAAs) containing phosphorous groups in the main chain were synthesized using different ratios of two diamines, i.e., bis(3-aminophenyl)methyl phosphine oxide (DAMPO) and 4,4′-oxydianiline (ODA), with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) by polycondensation in N,N′-dimethyacetamide (DMAc). The co-PAA solutions were spun into fibers by a dry-jet wet spinning process, and then polyimide copolymer (co-PI) fibers were obtained by thermal imidization. ATR-FTIR spectra and elemental analysis confirmed the chemical structure of PAA and PI fibers. The as-prepared PI fibers have smooth and dense surface as well as uniform diameter. Compared with the blank PI-0, the Tg values of co-PI fibers increased considerably with the increase in DAMPO content. TGA results indicated that the co-PI fibers possessed good thermal stability up to 510 °C and a residual char yield of up to 61% at 850 °C. All co-PI fibers exhibited excellent elongation, and their tensile strength and modulus can reach 0.9 GPa and 14.97 GPa when the molar ratio of DAMPO/ODA was 6/4 and the draw ratio was 3.0. The relationship between microstructure and mechanical property is also discussed.
- Zhao, Yong,Feng, Tao,Li, Guomin,Liu, Fangfang,Dai, Xuemin,Dong, Zhixin,Qiu, Xuepeng
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- Quaternary Phosphorus-Induced Iodocuprate(I)-Based Hybrids: Water Stabilities, Tunable Luminescence and Photocurrent Responses
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Four (triphenyl)phosphonium-based quaternary phosphorus salts with different substituents (varying from methyl to n-butyl) were selected to be structural directed agents (SDAs) to construct four iodocuprate(I) hybrids via solution method, i.e., [(PPh3Me)(Cu3I4)]n (1), [(PPh3Et)(Cu3I4)]n (2), (PPh3iPr)2(Cu2I4) (3), [(PPh3nBu)(Cu3I4)]n (4). The inorganic iodocuprates in 1, 2 and 4 are 1-D (Cu3I4)nn– chains constructed from Cu5I11 units, but (Cu2I4)2– in 3 is a di-nuclear cluster. Interestingly, the strength of Cu···Cu and π–π stacking interactions are weakened with the lengthening of alkyl groups on P-atom. The best water stability of 4 can be ascribed to the better hydrophobicity of n-butyl group, which deters the dispersing of organic and inorganic moieties and as a result, inhibit hydrolysis reaction. Furthermore, all compounds exhibit typical reversible luminescent thermochromic behaviors, among which 4 exhibits blue emission and the quenching of higher energy (HE) zone in 1 and 2 are led by strong π–π stacking interactions. Besides, effective and repeatable photocurrent responses can be detected in these compounds. In all, by systematically introducing alkyl groups into (triphenyl)phosphonium as SDAs to prepare hybrid iodocuprates, we can find that the longer alkyl groups can achieve stronger tunable PL materials with enhanced water stabilities.
- Zhang, Wen-Ting,Liu, Jian-Zhi,Liu, Jing-Bo,Song, Kai-Yue,Li, Yi,Chen, Zhi-Rong,Li, Hao-Hong,Jiang, Rong
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- Electrospray Mass Spectrometric Studies of Some Phosphonium Cations
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A series of methylphosphonium cations derived from mono- and polyphosphines were generated by interaction of the phosphine with methyl iodide.Electrospray mass spectra of the cations were obtained directly from dichloromethane-methanol solutions.In all cases the intact phosphonium cations were observed, often as the base peak, emphasizing the 'soft' nature of this type of ionization.Some of the polyphosphines showed additional peaks at m/z 16 and 32 units higher than the molecular ions due to oxidation of the non-methylated phosphine groups.Collisionally activated dissociation mass spectra show a consistent mode of fragmentation with the formation of alkene ions being dominant.Where comparisons are possible, there is a close correlation with the electron impact mass spectra of the neutral phosphines.
- Colton, Ray,Traeger, John C.,Harvey, Justin
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- Unexpected oxidative dimerisations of a cyclopentadienyl-phosphane formation of unprecedented, structurally remarkable phosphacyclic compounds
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The reactions of Me2PCp# (1) (Cp# = C 5HMe4) with Ph3PCH2X+ X-(X = Cl, Br, I) and diiodomethane as potential electrophiles have been investigated. Unexpectedly, in all four cases unprecedented oxidative dimerisations of the cyclopentadienylphosphane 1 have been observed. In the reactions with the phosphonium salts, an ionic group 15 analogue of octamethyl-tetrahydro-s-indacene with different: counterions X- has been obtained (5-7) as a result of X+ transfer and H+ elimination. In the reaction of 1 with dilodomethane a fourfold anellated, partially unsaturated, heterocyclic compound 9 exhibiting two spiro carbon centres, which are directly linked, was formed, presumably as a result of iodine radical transfer. Both of the novel phosphorus heterocycles have been characterised by means of single crystal XRD analysis.
- Lichtenberg, Crispin,Elfferding, Michael,Sundermeyer, Joerg
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- Solvent-dependent changes in the ene reaction of RTAD with alkenes: The cyclopropyl group as a mechanistic probe
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(Chemical Equation Presented) The vinylcyclopropyl moiety was used as an efficient probe to test mechanistic possibilities of the triazolinedione-alkene ene reaction. In non-hydroxylic solvents, this reaction afforded only the ene adducts via a closed three-membered aziridinium imide (Al) intermediate, whereas in hydroxylic solvents a dipolar intermediate is favored and trapped by the cyclopropyl moiety to form the corresponding cyclopropyl-rearranged solvent-trapped adducts.
- Roubelakis, Manolis M.,Vougioukalakis, Georgios C.,Angelis, Yiannis S.,Orfanopoulos, Michael
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- Stereoselective synthesis of (6Z,8E)-undeca-6,8,10-trien-3-one (yuzunone) for its characterization in yuzu and various citrus essential oils
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(6Z,8E)-Undeca-6,8,10-trien-3-one (yuzunone) is reported to be one of the main olfactory contributors of the specific fruity-green-balsamic odor of yuzu peel oil. Using an original stereoselective synthesis, we prepared a pure sample of yuzunone, which was used as a reference compound to check its presence by GC–MS and GC–O in 5 commercial samples of yuzu and citrus essential oils. Surprisingly, we could not detect yuzunone by GC–MS in any of our samples. However, it could be detected by a small part of the panelists involved in GC–O/AEDA experiments in a yuzu commercial oil, but its olfactory contribution proved to be very limited.
- Uehara, Ayaka,Baldovini, Nicolas
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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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Page/Page column 33
(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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- Iron Catalyzed Double Bond Isomerization: Evidence for an FeI/FeIII Catalytic Cycle
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Iron-catalyzed isomerization of alkenes is reported using an iron(II) β-diketiminate pre-catalyst. The reaction proceeds with a catalytic amount of a hydride source, such as pinacol borane (HBpin) or ammonia borane (H3N?BH3). Reactivity with both allyl arenes and aliphatic alkenes has been studied. The catalytic mechanism was investigated by a variety of means, including deuteration studies, Density Functional Theory (DFT) and Electron Paramagnetic Resonance (EPR) spectroscopy. The data obtained support a pre-catalyst activation step that gives access to an η2-coordinated alkene FeI complex, followed by oxidative addition of the alkene to give an FeIII intermediate, which then undergoes reductive elimination to allow release of the isomerization product.
- Woof, Callum R.,Durand, Derek J.,Fey, Natalie,Richards, Emma,Webster, Ruth L.
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supporting information
p. 5972 - 5977
(2021/03/17)
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- Highly Efficient and Convenient Access to Phosphinates via CHCl3-Assisted Direct Phosphorylation between R2P(O)H and ROH by Phosphonium Salt Catalysis
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A mild, efficient, convenient and scalable method to synthesize phosphinates via direct phosphorylation between R2P(O)H and ROH was developed. All aromatic substrates completed this transformation with excellent yields (up to 98 %), and preliminary mechanistic studies suggest that a carbene-involving process from CHCl3 to CH2Cl2 facilitates the phosphorylation.
- Jiang, Zhiyu,Wang, Tianli,Yu, Xiaojun,Zhang, Hong-Su,Zhang, Song
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supporting information
(2020/05/25)
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- Practical synthesis of phosphonium salts with orthoformates and their application as flame retardants in polycarbonate
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An efficient and practical approach to phosphonium salts has been developed. By the reaction of phosphines and different acid sources with orthoformates in one-step operation, the process allowed rapid access to phosphonium salts with diverse counterions in high yield after the purification by recrystallization. The flame retardant performance in PC has also been examined by blending several phosphonium salts to PC respectively. Phosphonium phosphates showed excellent flame retardancy in PC with only 2 phr blending.
- Jiang, Pingkai,Li, Tao,Xu, Chencong,Zhang, Yong Jian
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- Quaternary phosphonium salt flame retardant and synthesis method and application thereof
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The invention provides a quaternary phosphonium salt flame retardant and a synthesis method and application thereof, and the method comprises the following steps: by taking an acidic compound, ortho-formic acid trisubstituted ester and an organic phosphine compound III or IV as raw materials, carrying out a one-step reaction process to prepare the quaternary phosphonium salt flame retardant I or II. The flame retardant disclosed by the invention has good thermal stability and has an excellent flame-retardant effect when being applied to various polymers. The method is simple and convenient insynthesis operation, low in raw material price, mild in synthesis condition and high in yield. According to the synthesis method, introduction of halogen ions is avoided, and dozens of anions are successfully introduced. By adding a small amount of the flame retardant, the obtained PC flame-retardant composite material UL-94 can reach the V-0 grade.
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Paragraph 0220-0224
(2020/06/20)
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- Synthesis of Chiral Spin-Labeled Amino Acids
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Spin-labeled amino acids (SLAAs) are often used to determine intermolecular distances and conformations in proteins via double electron-electron resonance. Currently available SLAAs can be difficult to incorporate selectively and have little resemblance to natural side chains in proteins. Enantioselective synthesis of three spin-labeled l-amino acids is described, starting from readily available 2,2,6,6-tetramethyl-4-piperidinone. These SLAAs better replicate canonical residues in proteins and aim for biological incorporation via genetic incorporation or solid-phase peptide synthesis.
- Vuong, Wayne,Mosquera-Guagua, Fabricio,Sanichar, Randy,McDonald, Tyler R.,Ernst, Oliver P.,Wang, Lei,Vederas, John C.
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supporting information
p. 10149 - 10153
(2019/12/24)
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- A method for the preparation of entecavir (by machine translation)
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The invention discloses a compound of formula (I) shown in the method for the preparation of entecavir, the method according to the following steps: shown in formula (II) intermediate of the raw materials, as shown in formula (III) of the polystyrene load the high price of iodine is the oxidizing agent, in order to of a catalytic amount of N - hydroxy imide compound as co-oxidizing agent, under the action of the additive, in formula (I). The beneficial effect of the present invention is of relatively expensive the iodine passes through polystyrene after load, can be a simple filtration recovery, recycling, the production cost is low, the preparation method is suitable for industrial production. (by machine translation)
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Paragraph 0006; 0012
(2018/10/11)
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- ATP3 and MTP3: Easily Prepared Stable Perruthenate Salts for Oxidation Applications in Synthesis
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The Ley–Griffith tetra-n-propylammonium perruthenate (TPAP) catalyst has been widely deployed by the synthesis community, mainly for the oxidation of alcohols to aldehydes and ketones, but also for a variety of other synthetic transformations (e.g. diol cleavage, isomerizations, imine formation and heterocyclic synthesis). Such popularity has been forged on broad reaction scope, functional group tolerance, mild conditions, and commercial catalyst supply. However, the mild instability of TPAP creates preparation, storage, and reaction reproducibility issues, due to unpreventable slow decomposition. In search of attributes conducive to catalyst longevity an extensive range of novel perruthenate salts were prepared. Subsequent evaluation unearthed a set of readily synthesized, bench stable, phosphonium perruthenates (ATP3 and MTP3) that mirror the reactivity of TPAP, but avoid storage decomposition issues.
- Moore, Peter W.,Read, Christopher D. G.,Bernhardt, Paul V.,Williams, Craig M.
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supporting information
p. 4556 - 4561
(2018/03/13)
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- Copper-Catalyzed Oxidative Difunctionalization of Terminal Unactivated Alkenes
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The copper(II)-promoted free-radical oxidative difunctionalization of terminal alkenes to access ketoazides by utilizing molecular oxygen has been reported. A series of styrene derivatives have been evaluated and were found to be compatible to give the desired difunctionalized products in moderate to good yields. The role of molecular oxygen both as an oxidant and oxygen atom source in this catalytic transformation has been unquestionably demonstrated by 18O-labeling studies and a radical mechanistic pathway involving the oxidative formation of azidyl radicals is also designed. This environment-friendly catalytic oxidative protocol can transform aldehyde to nitrile.
- Hussain, Muhammad Ijaz,Feng, Yangyang,Hu, Liangzhen,Deng, Qingfu,Zhang, Xiaohui,Xiong, Yan
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p. 7852 - 7859
(2018/05/30)
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- Process for preparing biphenyl compounds
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The present invention relates to a process for preparing a compound having the formula (I), said process comprising the following steps: a) the addition of an oxygen source into a solution of a compound of formula (II), in a water-miscible solvent, b) the addition of a laccase in the solution obtained after step a); and c) the possible recovering of the compound of formula (I) thus obtained.
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Page/Page column 29; 30
(2019/01/04)
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- Synthesis of 2,2-diarylvinyl phenyl selenides by dehydration of 2-hydroxyalkyl phenyl selenides
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A novel route to 2,2-diarylvinyl phenyl selenides is reported by dehydration of the corresponding 2,2-diaryl-2-hydroxyethyl phenyl selenides, prepared by oxyphenylselenenylations of the corresponding 1,1-diarylethylenes, upon treatment with p-toluenesulfonic acid.
- Stuhr-Hansen, Nicolai
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- Production of cyclic carbonate
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The purpose of the present invention is to provide a practical method for producing a cyclic carbonate, which is widely used for various applications such as electrolytic solutions for lithium-ion secondary batteries and plastic materials, by a reaction between an epoxide (oxirane) and carbon dioxide, the method giving consideration to the reduction of environmental loads and making it possible to produce said cyclic carbonate with high yield under mild conditions, such as at room temperature and atmospheric pressure. The present invention relates to a method for producing a cyclic carbonate, the method being characterized by reacting an epoxide and carbon dioxide in the presence of an iodine-anion-containing phosphonium salt and a compound including a hydrogen atom that can form a hydrogen bond with an oxygen atom in the epoxide.
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Paragraph 0124
(2017/11/08)
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- PERMANENTLY GRAFTED GLACIOPHOBIC NANOMATERIALS AND METHODS OF MAKING
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The present disclosure provides for substrates for glaciophobic polymer-nanoparticle composites, glaciophobic polymer-nanoparticle composites, methods of making glaciophobic polymer-nanoparticle composites, methods of making films on substrates, and the like.
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Page/Page column 12
(2017/09/02)
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- Metal-free synthesis of 2-aminonaphthalenes by intramolecular transannulation of 1-sulfonyl-4-(2-alkenylphenyl)-1,2,3-triazoles
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A facile metal-free synthesis of naphthalenes by intramolecular transannulation of 1-sulfonyl-4-(2-alkenylphenyl)-1,2,3-triazoles was realized. The in situ formed ketenimine was proposed as the key intermediate, and the desired 2-aminonaphthalenes were generated in up to 87% yield in refluxing 1,2-dichloroethane without any catalyst or additive.
- Xu, Ze-Feng,Yu, Xing,Yang, Dongdong,Li, Chuan-Ying
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supporting information
p. 3161 - 3164
(2017/04/21)
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- Palladium-catalyzed synthesis of monofluoroalkenes from 3,3-difluoropropenes using dimethylmalonate and derivatives as nucleophiles
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The synthesis of monofluoroalkenes bearing a malonate or its derivatives at the β position is presented. The reaction can be performed with various 3,3-difluoropropenes. A preliminary result for an enantioselective variant is also reported. Further synthetic transformations of a monofluoroalkene were also accomplished.
- Drouin, Myriam,Tremblay, Sébastien,Paquin, Jean-Fran?ois
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supporting information
p. 2376 - 2384
(2017/03/20)
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- Permanently grafted icephobic nanocomposites with high abrasion resistance
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In this work, a series of copolymer/silica nanocomposites are investigated that exhibit excellent anti-icing behavior and can be covalently grafted to any substrate containing C-H bonds with high durability. The copolymers of interest consist of pendant benzophenone, hexafluorobutyl, and a variety of other comonomers that, under mild UV irradiation, can be covalently grafted on a variety of substrates and generate a densely cross-linked network of polymer and well-dispersed nanoparticles. The robustness of thin films was compared in a series of terpolymers with different acrylic comonomer content. Thin films prepared with tert-butyl ester side groups had less backbone chain scission and, therefore, a greater extent of cross-linking than films prepared with n-butyl ester side groups. The iso-butyl acrylate comonomer promotes photoreaction efficiency in terms of kinetic rate and network robustness, leading to films that can sustain high shear forces and abrasion. The anti-icing capability of the composite was investigated using the impact of supercooled water on different substrates. The composite maintains its icephobicity after modified Taber testing with multiple abrasion cycles using a 300 g load, which demonstrates excellent mechanical resistance. In addition, this study has led to rational design rules for copolymers that maximize permanent attachment of different surface functionalities in terms of both grafting density and reaction kinetics.
- Gao, Jing,Martin, Andrew,Yatvin, Jeremy,White, Evan,Locklin, Jason
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p. 11719 - 11728
(2016/08/04)
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- Design, synthesis and SAR study of novel sulfonylureas containing an alkenyl moiety
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A series of sulfonylurea compounds was designed and synthesized via introducing an alkenyl moiety into the aryl-5 position and most title compounds exhibited enhanced antifungal activities and limited herbicidal activities compared with chlorsulfuron. Then, a CoMSIA calculation for antifungal activities was carried out to establish a 3D-QSAR model in which a cross-validated q2 of 0.585 and a correlation coefficient r2 of 0.989 were obtained. The derived model revealed that hydrophobic and electrostatic fields were the two most important factors for antifungal activity. Structure optimization was performed according to the CoMSIA model and compound 9z was found to be as potent as chlorothalonil in vitro against C. cornigerum, the pathogen of the wheat sharp eyespot disease. In order to study the fungicidal mechanism, 9z was successfully docked into yeast AHAS using a flexible molecular docking method and the resulting binding pattern was similar to that of chlorimuron-ethyl, indicating that the antifungal activity of compounds 9 was probably due to the inhibition of fungal AHAS.
- Wei, Wei,Cheng, Dandan,Liu, Jingbo,Li, Yuxin,Ma, Yi,Li, Yonghong,Yu, Shujing,Zhang, Xiao,Li, Zhengming
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p. 8356 - 8366
(2016/09/09)
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- A transition-metal-free Heck-type reaction between alkenes and alkyl iodides enabled by light in water
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A transition-metal-free coupling protocol between various alkenes and non-activated alkyl iodides has been developed by using photoenergy in water for the first time. Under UV irradiation and basic aqueous conditions, various alkenes efficiently couple with a wide range of non-activated alkyl iodides. A tentative mechanism, which involves an atom transfer radical addition process, for the coupling is proposed.
- Liu, Wenbo,Li, Lu,Chen, Zhengwang,Li, Chao-Jun
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supporting information
p. 6170 - 6174
(2015/06/08)
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- A Palladium(II)-Catalyzed C-H Activation Cascade Sequence for Polyheterocycle Formation
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Polyheterocycles are found in many natural products and are useful moieties in functional materials and drug design. As part of a program towards the synthesis of Stemona alkaloids, a novel palladium(II)-catalyzed C-H activation strategy for the construction of such systems has been developed. Starting from simple 1,3-dienyl-substituted heterocycles, a large range of polycyclic systems containing pyrrole, indole, furan and thiophene moieties can be synthesized in a single step. Don't overdo it: A palladium(II)-catalyzed C-H activation cascade sequence for the synthesis of polyheterocycles is reported. Aromatization of the initially formed dihydro species occurred with a quinone oxidant. In some cases the use of one equivalent of the oxidant enabled isolation of the dihydro species as a single isomer (see scheme; X=NMe, O, S).
- Cooper, Stephen P.,Booker-Milburn, Kevin I.
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supporting information
p. 6496 - 6500
(2015/06/02)
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- Organoselenium-catalyzed, hydroxy-controlled regio- and stereoselective amination of terminal alkenes: Efficient synthesis of 3-amino allylic alcohols
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An efficient route to prepare 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of bases by orangoselenium catalysis has been developed. In the absence of bases α,β-unsaturated aldehydes were formed in up to 97% yield. Control experiments reveal that the hydroxy group is crucial for the direct amination.
- Deng, Zhimin,Wei, Jialiang,Liao, Lihao,Huang, Haiyan,Zhao, Xiaodan
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supporting information
p. 1834 - 1837
(2015/04/27)
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- 2-Pyridyl-phosphine and -diphosphine complexes of nickel(0), their reactivity (including aqueous solution chemistry), and some related, incidental methylphosphonium iodides
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The chemistry of Ni0-dicarbonyl(pyridylphosphine) complexes of the type Ni(CO)2L2, where L is either P-bonded PPh3-npyn (n = 1-3, py = 2-pyridyl; abbreviated PNx, x = 1-3, species 1a-c), or L2 is (P-P)-chelated py2P(CH2)2Ppy2 or, is further developed from earlier studies by our group [the P-P ligands are abbreviated, respectively, as d(py)pe and d(py)pcp]. The complexes are synthesized from C6H6 solutions of Ni(CO)2(PPh3)2, and the Ni(CO)2(PPh3)(PNx) intermediates (1a-c) are detected; Ni(CO)2[d(py)pcp] (2b) is shown by X-ray analysis to have a distorted tetrahedral structure; and the NiII species [Ni2(CO)4(μ-PN2)2]Cl4 is isolated from a light-induced reaction in CDCl3 solution. Complex 2b dissolves in water at ambient conditions via a net double protonation of pyridyl N-atoms, the {Ni(CO)2[2H-d(py)pcp]}2+ being isolated as the bis(triflate) salt; the dication decomposes in minutes with formation of [Ni(H2O)6]2+, CO, the phosphine dioxide, and deprotonated d(py)pcp. Some twenty-two Ni0 complexes, exemplified by Ni(P-P)2, Ni(PNx)2(P-P), Ni(PNx)4, and related PPh3- and Ph2P(CH2)2PPh2 (dppe)-containing species, are synthesized from Ni(1,5-COD)2 and their reactivity studied; for example, oxidative addition of MeI generates trans-Ni(Me)(I)(PN3)2 and trans-Ni(Me)(I)(P-P)2 but, with non-pyridyl containing reactants such as Ni(PPh3)4 and Ni(dppe)2, only (monomethyl)phosphonium iodides are formed. Such iodides, and the bis(methyl) analogues [(CH3)2(diphosphine)]I2, are then studied for clarification of some observed Ni chemistry. The NMR trends (a)-(d) are noted within the series of Ni0 complexes, and are rationalized: (a) the 2JPP values in 1a-c, and the separation between the two doublets, parallel the number of N-atoms present; (b) the 31P{1H} signals in the Ni(PNx)4 and Ni(PNx)2(P-P) complexes shift downfield in the order PN1 2 3 within linear dependences; (c) the 2JPP values for the Ni(PR3)2(P-P) complexes (R = Ph and PNx) decrease in the order R = Ph > PN1 > PN2 > PN3; (d) and the separation between the two 31P{1H} triplets of the Ni(PNx)2(P-P) complexes generally depends on the relative numbers of phenyl and pyridyl groups.
- Le Page, Matthew D.,Patrick, Brian O.,Rettig, Steven J.,James, Brian R.
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p. 276 - 288
(2015/06/02)
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- Novel Resveratrol-Based Aspirin Prodrugs: Synthesis, Metabolism, and Anticancer Activity
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(Graph Presented). Regular aspirin use has been convincingly shown to reduce the risk of colorectal cancer. However, long-term use of aspirin leads to gastrotoxicity. Herein, we designed and synthesized a novel class of resveratrol-based aspirin prodrugs to simultaneously release aspirin and resveratrol to attenuate the side effects caused by aspirin. Prodrug RAH exerted enhanced anticancer activities which are better than a physical mixture of aspirin and resveratrol as well as each individually. Metabolism of RAH in mice showed that the majority of RAH is decomposed to release resveratrol and aspirin or salicylic acid either in the intestine or after absorption. Mechanistic studies demonstrate RAH inhibits cell cycle arrest through downregulation of cyclins and induces apoptosis by activation of caspase-3 in cancer cells. These findings highlighted the improved anticancer properties of resveratrol-based aspirin prodrugs. RAH may represent novel and safe alternatives of aspirin for the purpose of daily use in the future.
- Zhu, Yingdong,Fu, Junsheng,Shurlknight, Kelly L.,Soroka, Dominique N.,Hu, Yuhui,Chen, Xiaoxin,Sang, Shengmin
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p. 6494 - 6506
(2015/09/08)
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- β-Amyrin Biosynthesis: The Methyl-30 Group of (3S)-2,3-Oxidosqualene Is More Critical to Its Correct Folding to Generate the Pentacyclic Scaffold than the Methyl-24 Group
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Oxidosqualene cyclases catalyze the transformation of oxidosqualene (1) into numerous cyclic triterpenes. Enzymatic reactions of 24-noroxidosqualene (8) and 30-noroxidosqualene (9) with Euphorbia tirucalli β-amyrin synthase were conducted to examine the role of the branched methyl groups of compound 1 in the β-amyrin biosynthesis. Substrate 8 almost exclusively afforded 30-nor-β-amyrin (>95.5%), which was produced through a normal cyclization pathway, along with minor products (4.5%). However, a lack of the Me-30 group (analogue 9) resulted in significantly high production of premature cyclization products, including 6/6/6/5-fused tetracyclic and 6/6/6/6/5-fused pentacyclic skeletons (64.6%). In addition, the fully cyclized product (35.4%) having the 6/6/6/6/6-fused pentacycle was produced; however, the normally cyclized product, 29-nor-β-amyrin was present in only 18.6% of these products. The conversion yield of substrate 8 possessing a Z-Me group at the terminus was approximately twofold greater than that of compound 9 with an E-Me group. Thus, the Me-30 group is essential for the correct folding of a chair-chair-chair-boat-boat conformation of compound 1 for the production of the β-amyrin scaffold, whereas the Me-24 group exerts little influence on the normal polycyclization cascade. Here, we show that the Me-30 group plays critical roles in constructing the ordered architecture of a chair-chair-chair-boat-boat structure, in facilitating the ring-expansion reactions, and in performing the final deprotonation reaction at the correct position.
- Hoshino, Tsutomu,Miyahara, Yuri,Hanaoka, Masaki,Takahashi, Kazunari,Kaneko, Ikki
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supporting information
p. 15769 - 15784
(2015/11/03)
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- The mechanism of the first step of the Mitsunobu reaction
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Previous DFT calculations employing phosphine (PH3) and dimethyl azodicarboxylate showed that a cyclic O,N-phosphorane was energetically favored relative to betaine formation. In this study strong experimental support for the formation of the phosphorane is described. The question of whether betaine formation occurs via nucleophilic attack of the phosphine on the azodicarboxylate as has been previously assumed, or via a [4+2] cycloaddition (cheletropic) reaction to give the O,N-phosphorane, followed by ring-opening to give the betaine has not been resolved. An answer to this intriguing question is provided.
- Camp, David,Von Itzstein, Mark,Jenkins, Ian D.
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p. 4946 - 4948
(2015/06/23)
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- Effective synthesis of cyclic carbonates from carbon dioxide and epoxides by phosphonium iodides as catalysts in alcoholic solvents
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Phosphonium iodides effectively catalyzed the reaction of CO2 and epoxides under mild conditions such as ordinary pressure and ambient temperature in 2-propanol, and the corresponding five-membered cyclic carbonates were obtained in high yields.
- Aoyagi, Naoto,Furusho, Yoshio,Endo, Takeshi
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supporting information
p. 7031 - 7034
(2013/12/04)
-
- Stereoselective total synthesis of both (6R,9R,10S,7E)- and (6S,9R,10S,7E)-epimers of oxylipin (9R,10S,7E)-6,9,10-trihydroxyoctadec-7-enoic acid
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An asymmetric synthesis of both the stereoisomers (2a & 2b) of the structure 2 proposed for (9R,10S,7E)-6,9,10-trihydroxyoctadec-7-enoic acid, an immunostimulant oxylipin from the n-butanol extract of the corms of Dracontium loretense, has been accomplished. The key steps involved are using Jacobsen's hydrolytic kinetic resolution (HKR), Julia-Kocienski olefination, regioselective epoxide ring opening and Wittig olefination. The configuration (9R,10S,7E)-6,9,10-trihydroxyoctadec-7-enoic acid was established as 2a from comparison of NMR data, HPLC analysis and [α]D values of naturally derived (9R,10S,7E)-6,9,10-trihydroxyoctadec-7-enoic acid, and comparison with the synthetic diastereomers 2a and 2b.
- Saikia, Bishwajit,Devi, Thongam Joymati,Barua, Nabin C.
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p. 2157 - 2166
(2013/03/14)
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- Highly selective Wacker reaction of styrene derivatives: A green and efficient aerobic oxidative process promoted by benzoquinone/NaNO 2/HClO4 under mild conditions
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A green and efficient catalytic redox system for the aerobic oxidative Wacker oxidation of styrene derivatives at room temperature using molecular oxygen as the terminal oxidant without copper chloride has been developed. The newly developed system exhibited excellent catalytic activity for the smooth transformation of terminal styrene derivatives to the desired methyl ketones with up to 96% yield and >99% selectivity. The Royal Society of Chemistry 2013.
- Zhang, Guofu,Xie, Xiaoqiang,Wang, Yong,Wen, Xin,Zhao, Yun,Ding, Chengrong
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supporting information
p. 2947 - 2950
(2013/07/25)
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- Preparation, structure, and reactivity of dipalladium(I) complexes containing the carbanion 2-C6F4PPh2: Coexistence of distinct, noninterconverting head-to-head [dipalladium(0/II)] and head-to-tail [dipalladium(I)] species
-
Comproportionation of trans-[Pd(κ2-2-C6F 4PPh2)2] with [PdL4] (L = PPh 3, AsPh3) gives metal-metal-bonded dipalladium(I) complexes [Pd2I(μ-2-C6F4PPh 2)2(L)2] [L = PPh3 (5), AsPh 3 (6)] in which the bridging ligands adopt a head-to-tail arrangement. The corresponding diplatinum(I) complex [Pt2 I(μ-2-C6F4PPh2) 2(PPh3)2] (9) is obtained similarly from [Pt(κ2-2-C6F4PPh2) 2] and [Pt(PPh3)3]. The separations between the metal atoms in the dipalladium(I) complexes [2.5740(3) A (5), 2.5511(3) A (6)] are slightly less than that in the diplatinum(I) complex 9 [2.61179(15) A]. The axial triphenylarsine ligands of 6 are replaced by tert-butyl isocyanide to give the dipalladium(I) complex [Pd2 I(μ-2-C6F4PPh2) 2(CNtBu)2] (7). However, treatment of trans-[Pd(κ2-2-C6F4PPh2) 2] with [Pd(CNtBu)2], generated in situ from a mixture of tert-butyl isocyanide and [Pd(η5-Cp) (η3-allyl)], gives a formally mixed-valent palladium(0)- palladium(II) complex [Pd20/II(μ-2-C6F 4PPh2)2(CNtBu)2] (8), in which the bridging ligands are arranged head-to-head. In contrast, comproportionation of [Pt(κ2-2-C6F 4PPh2)2] with [Pt3(CN tBu)6] gives the diplatinum(I) complex [Pt 2I(μ-2-C6F4PPh2) 2(CNtBu)2] (10) analogous to 7; there was no evidence for the formation of a dinuclear mixed-valent species. Although complexes 7 and 8 are isomers, with similar Pd-Pd separations [2.5803(4) A (7), 2.5580(2) A (8)], they do not interconvert in solution. The diplatinum(I) complex 9 undergoes oxidative addition with iodine to give an A-frame cation, [Pt2(μ-I)(μ-2-C6F 4PPh2)2(PPh3)2] +, isolated as its PF6- salt (11). In contrast, the dipalladium(I) complex 5 eliminates one of the PPh3 ligands when it undergoes oxidative addition with halogens and with methyl iodide, the products being A-frame dipalladium(II) complexes [Pd2X(μ-Y)(μ- 2-C6F4PPh2)2(PPh3)] [X = Y = I (12), Cl (13); X = Me, Y = I (14)]. The metal-metal distances in 11-14 [2.9478(5) A (11), 2.8078(7) A (12), 2.8241(3) A (13), and 2.8013(5) A (14)] are ca. 0.3 A greater than in their dimetal(I) precursors, consistent with a weaker metal-metal interaction in the dimetal(II) complexes. Unexpectedly, reaction of 5 with iodobenzene gives a mononuclear palladium(II) complex, cis-[Pd(κ2C,P-2-C6F 4PPh2)(κC-2-C6F4PPh 2)(PPh3)] (15). This is suggested to be formed by a sequence of (a) oxidative addition of iodobenzene to 5 to give a σ-phenyl complex analogous to the σ-methyl complex 14, (b) a change in the binding mode of one of the 2-C6F4PPh2 ligands from μ- to κ2-, and (c) reductive elimination of tetraphenylphosphonium iodide and loss of Pd(0).
- Bhargava, Suresh K.,Priver, Steven H.,Willis, Anthony C.,Bennett, Martin A.
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p. 5561 - 5572,12
(2020/08/31)
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- Powerful insight into catalytic mechanisms through simultaneous monitoring of reactants, products, and intermediates
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Keeping an eye on all the players: The combination of bulky phosphonium tags and pressurized sample infusion transforms electrospray ionization mass spectrometry into a tool capable of producing dense data on the relative concentrations of all components of a catalytic reaction, such as the palladium-catalyzed coupling of an aryl iodide with phenylacetylene (see graph).
- Vikse, Krista L.,Ahmadi, Zohrab,Manning, Cara C.,Harrington, David A.,McIndoe, J. Scott
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supporting information; experimental part
p. 8304 - 8306
(2011/10/31)
-
- Thermogravimetrical investigations of the dealkoxycarbonylation of N-acyl-α-triphenylphosphonioglycinates
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Thermogravimetrical experiments revealed that immediately after the endothermic process of the melting of N-acyl-α- triphenylphosphonioglycinates 1, an exothermic demethoxycarbonylation of phosphonioglycinates commenced, accompanied by the release of CO2. The residues contained the corresponding N-acylaminomethyltriphenylphosphonium salts 2 (18.3-49.5%), methyltriphenylphosphonium salts 7 (21.8-67.9%), and the corresponding 1,2-di(N-acylamino)fumaric acid dimethyl ester 6 (2.1-26.0%). When the reaction was carried out in the presence of Ph3P and the corresponding triphenylphosphine hydrobromide, hydroiodide, or tetrafluoroborate, N-acyl-α-triphenylphosphoniumglycinate bromides and iodides 1a-f underwent demethoxycarbonylation to form the corresponding N-acylaminomethyltriphenylphosphonium salts 2a-f at 95-130 °C in good to excellent yields (79-100%). On the other hand, tetrafluoroborates 1g-i underwent corresponding reactions at about 170-175 °C to give phosphonium tetrafluoroborates 2g-i in much lower yields (34-67%). Plausible mechanisms of the investigated reaction are discussed. It was also demonstrated that the obtained crude α-(N-acylamino)alkyltriphenylphosphonium salts 2 could be applied as valuable α-amidoalkylating agents in spite of their contamination with inert methyltriphenylphosphonium salts 7.
- Adamek, Jakub,Mrowiec-Bia?on?, Julita,Pa?dzierniok-Holewa, Agnieszka,Mazurkiewicz, Roman
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experimental part
p. 22 - 27
(2011/02/26)
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- New methodology for the conversion of epoxides to alkenes
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Epoxides have been transformed in good yields to alkenes by a process involving (i) ring-opening of the epoxide with 2-mercaptobenzothiazole, (ii) oxidation of the derived ss-hydroxy thioethers to the corresponding sulfones, and (iii) thermal or base-promoted fragmentation of these sulfones to alkenes. The stereochemistry of the starting epoxide is transfer-red faithfully to the alkene product, because of the SN2 epoxide ring-opening reactions and the antiperiplanar SO2 elimination reaction of the ss- alkoxysulfinate intermediates. This methodology may form the basis of a new protecting group strategy for alkenes.
- Wu, Feng-Ling,Ross, Benjamin P.,McGeary, Ross P.
-
experimental part
p. 1989 - 1998
(2010/06/15)
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- Activation of allylic C-F bonds: Palladium-catalyzed allylic amimation of 3,3-difluoropropenes
-
(Chemical Equation Present) Lose one, keep one! A wide range of cyclic and acyclic ss-aminofluoroalkenes are prepared by the title reaction. The key fluorinated palladium π-allyl intermediate is generated using a catalytic allylic C-F bond activation.
- Pigeon, Xavier,Bergeron, Maxime,Barabe, Francis,Dube, Pascal,Frost, Heather N.,Paquin, Jean-Francois
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supporting information; experimental part
p. 1123 - 1127
(2010/05/17)
-
- Basic hydrolysis of 1,4-bis(triphenylphosphonio)buta-1,3-diene dihalides
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Basic hydrolysis of 1,4-bis(triphenylphosphonio)buta-1,3-diene dichloride with 10% NaOH gave isomeric 4-diphenylphosphoryl-4-phenylbut-1(2)-enes and 1-diphenylphosphoryl-1-phenylbuta-1,3-diene, the products of anionotropic migration of a phenyl group from the P atom to the -position. Hydrolysis with Na2CO3 afforded only the diene product. In both cases, triphenylphosphine and triphenylphosphine oxide were isolated as secondary products. Dehydrochlorination of 2-chloro-1,4-bis(triphenylphosphonio) but-2-ene dibromide with triphenylphosphine was proposed as a new convenient route to 1,4-bis(triphenylphosphonio)buta-1,3-diene dibromide.
- Ovakimyan,Pogosyan,Movsisyan,Indzhikyan
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experimental part
p. 560 - 564
(2011/02/17)
-
- PROCESS FOR PRODUCING HIGH PURITY EXO-ALKENYLNORBORNENE
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Embodiments of the present invention are directed generally to methods for producing high purity exo-alkenylnorbornenes from a mixture of conformational isomers thereof.
- -
-
Page/Page column 17
(2009/07/02)
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- Reaction of 2,4-dinitrophenylhydrazones of triphenyl(2-aroylethyl) phosphonium bromides with aqueous alkali and some transformations of the betaines formed
-
Triphenyl(2-p-toluoylethyl)- and triphenyl(2-p-bromobenzoylethyl) phosphonium bromide 2,4-dinitrophenylhydrazones were established to form a bipolar compounds with a negatively charged nitrogen atom and a positively charged phosphonium atom, under the act
- Khachikyan, R. Dzh.
-
experimental part
p. 88 - 91
(2009/05/30)
-
- Solvent-dependent changes in the triazolinedione-alkene ene reaction mechanism
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The influence of the solvent on the triazolinedione-alkene ene reaction mechanism has been investigated. Both inter- and intramolecular kinetic isotope effects with tetramethylethylenes and 2,2,2-(trideuterio)methyl-7-methyl-2,6- octadiene-[D3]-1,1,1 provide, for the first time, strong evidence for changes in the mechanism of the reaction on going from non-protic to polar protic solvents. In non-protic polar or apolar solvents, an aziridinium imide that equilibrates to an insignificant extent with an open intermediate (a dipolar or a polarized biradical) is formed irreversibly in the first, rate-determining step of the reaction, which is followed by fast hydrogen abstraction. On the contrary, in polar protic solvents, hydrogen abstraction is rate limiting, allowing the main dipolar intermediate to equilibrate with its open intermediate(s) as well as with the starting reagents.
- Vougioukalakis, Georgios C.,Roubelakis, Manolis M.,Alberti, Mariza N.,Orfanopoulos, Michael
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experimental part
p. 9697 - 9705
(2009/10/17)
-
- Facile SN2′ coupling reactions of Wittig reagents with dimethyl bromomethylfumarate: Synthesis of enes, dienes, and related natural products
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(Chemical Equation Presented) A new simple and efficient synthetic protocol with an ample scope has been demonstrated, by employing SN2′ coupling reactions of a variety of Wittig reagents with dimethyl bromomethylfumarate to obtain the corresponding enes, dienes, and related natural and unnatural products.
- Patel, Ramesh M.,Argade, Narshinha P.
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p. 4900 - 4904
(2008/02/07)
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- Enantioconvergent hydrolysis of styrene epoxides by newly discovered epoxide hydrolases in mung bean
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Two novel epoxide hydrolases were discovered in mung bean (Phaseolus radiatus L.) for the first time, either of which can catalyze enantioconvergent hydrolysis of styrene epoxides. Their regioselectivity coefficients are more than 90% for the p-nitrostyrene oxide. Furthermore, the crude mung bean powder was also shown to be a cheap and practical biocatalyst, allowing a one-step asymmetric synthesis of chiral (R)-diols from racemic epoxides, in up to >99% ee and 68.7% overall yield (after recrystallization).
- Xu, Wei,Xu, Jian-He,Pan, Jiang,Gu, Qing,Wu, Xin-Yan
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p. 1737 - 1740
(2007/10/03)
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- Photochemical generation of highly destabilized vinyl cations: The effects of α- and β-trifluoromethyl versus α- and β-methyl substituents
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(Chemical Equation Presented). The photochemical reactions in methanol of the vinylic halides 1-4, halostyrenes with a methyl or a trifluoromethyl substituent at the α- or β-position, have been investigated quantitatively. Next to E/Z isomerization, the reactions are formation of vinyl radicals, leading to reductive dehalogenation products, and formation of vinyl cations, leading to elimination, nucleophilic substitution, and rearrangement products. The vinyl cations are parts of tight ion pairs with halide as the counterion. The elimination products are the result of β-proton loss from the primarily generated α-CH3 and α-CF3 vinyl cations, or from the α-CH3 vinyl cation formed from the β-CH3 vinyl cation via a 1,2-phenyl shift. The β-CF 3 vinyl cation reacts with methanol yielding nucleophilic substitution products, no migration of the phenyl ring producing the α-CF3 vinyl cation occurs. The α-CF3 vinyl cation, which is the most destabilized vinyl cation generated thus far, gives a 1,2-fluorine shift in competition with proton loss. The experimentally derived order of stabilization of the vinyl cations photogenerated in this study, α-CF3 3 3 3, is corroborated by quantum chemical calculations, provided the effect of solvent is taken into account.
- Van Alem, Kaj,Belder, Geerte,Lodder, Gerrit,Zuilhof, Han
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p. 179 - 190
(2007/10/03)
-
- A Second-Generation Synthesis of the C1-C28 Portion of the Altohyrtins (Spongistatins)
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A practical second-generation synthesis of an advanced intermediate in our total synthesis of altohyrtin C (spongistatin 2) has been developed. A new approach to the C1-C15 (AB) portion features a vinyllithium addition to an aldehyde followed by a palladium-catalyzed allylic reduction to install the troublesome C13-C15 segment. Our general approach to the C16-C28 (CD) spiroketal has been retained, but some improvements have been made. Most notably, the kinetically controlled CD-spiroketalization reaction now proceeds in high yield with excellent diastereoselection. This new strategy uses the anti-aldol coupling used in our first-generation synthesis to join AB and CD fragments. A total of 9.6 g of intermediate 57 has been produced using this improved route.
- Hubbs, Jed L.,Heathcock, Clayton H.
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p. 12836 - 12843
(2007/10/03)
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- Synthesis and properties of phosphabetaine structures: III. Phosphabetaines derived from tertiary phosphines and α,β-unsaturated carboxylic acids. Synthesis, structure, and chemical properties
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Methods of synthesis of acylate phosphabetaines by reactions of triphenylphosphine with methacrylic, cinnamic, and p-methoxycinnamic acids are developed. The phosphabetaine form is proposed to exist in equilibrium with the (σ5-oxaphospholane form. The features of methylation of the phosphabetaines are discussed.
- Galkin,Bakhtiyarova,Polezhaeva,Galkina,Cherkasov,Krivolapov,Gubaidullin,Litvinov
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p. 384 - 389
(2007/10/03)
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- Microwave irradiation in organophosphorus chemistry. III. Moderate scale synthesis of reagents for olefin formation
-
Representative phosphonates and phosphonium salts have been prepared on a moderate scale (25-50 g) using a domestic microwave oven. The reactions, conducted in sealed hydrogenation vessels, showed remarkable rate acceleration and excellent yields (>95%) employing this methodology.
- Kiddle
-
p. 3377 - 3382
(2007/10/03)
-
- Synthesis of polyhydroxysterols (I): Synthesis of 24-methylenecholest-4-en-3β,6β-diol, a cytotoxic natural hydroxylated sterol
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Starting from stigmasterol (2), 24-methylenecholest-4-en-3β,6β-diol (1), a cytotoxic natural dihydroxylated sterol, was synthesized via 10 steps in 20% overall yield. The introduction of a side-chain of sterol was achieved by solid-liquid phase-transfer Wittig reaction using (3-methyl-2-oxo)butyltriphenylarsonium bromide (12) and K2CO3. Construction of the steroidal nucleus was finished by the addition of 3β-acetoxycholest-5,6-en-24-one (7) with NBA in dioxane under ambient temperature and by the elimination of 3β, 6β-diacetoxy-5a-bromocholestane-24-one (9). The spectral data of the synthetic product (1) are completely consistent with those of the natural compound (1). Copyright (C) 2001 Elsevier Science Inc.
- Cui, JianGuo,Zeng, LongMei,Su, JingYu,Lu, WeiGang
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