- En route to stable all-carbon-substituted silylenes: Synthesis and reactivity of a bis(α-spirocyclopropyl)silylene
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The synthesis of a bis(α-spirocyclopropyl)silylene is reported and its reactivity revealed. Liberation of the silylene was accomplished by UV-light-mediated photolysis of a trisilane precursor. Insertion and addition reactions prove the existence and versatility of this new family of bis(α-spirocyclopropyl)-substituted silylenes. Substitution on the flanking cyclopropyls for improved steric shielding of the reactive center remains challenging.
- Redies, Kai M.,Fallon, Thomas,Oestreich, Martin
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- Synthesis, crystal and structural characterization, Hirshfeld surface analysis and DFT calculations of three symmetrical and asymmetrical phosphonium salts
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Three stable phosphonium salts of 1,4-butanediylebis(triphenylphosphonium) dibromide I, butane-4?bromo-1-(triphenylphosphonium) bromide II and 1,3-propanediylbis(triphenylphosphonium) tetrahydroborate III were synthesized and structurally characterized. Single crystal X-ray diffraction analysis, spectroscopic methods and thermal analysis methods were used for the characterization of titled compounds. Crystallographic data showed that compound I crystallized in the triclinic crystal system with Pī space group and compound II crystallized in the monoclinic crystal system with P21/c space group. The crystal packing structures of I and II were stabilized by various intermolecular interactions, especially of C–H···π contacts. The molecular Hirshfeld surface analysis and 2D fingerprint revealed that the C···H contacts have 24.3% and 18.4% contributions in the crystal packings of compounds I and II, respectively. In addition, the H···Br (28.5%) contact has a considerable contribution to the crystal architecture of compound II. Theoretical studies were performed by DFT method to investigate the structural properties of the titled compounds. The isotopic ratio of boron in tetrahydroborate anion of compound III calculated by 1H NMR spectroscopy. The isotopic ratio for 10B/11B was 19.099 / 80.900%. Reduction of some carbonyl compounds to corresponding alcohols was performed by compound III and the optimum conditions were determined.
- Delaram, Behnaz,Gholizadeh, Mostafa,Makari, Faezeh,Nokhbeh, Seyed Reza,Salimi, Alireza
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- Evaluation of bifunctional chiral phosphine oxide catalysts for the asymmetric hydrosilylation of ketimines
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A series of bifunctional phosphine oxides have been prepared and evaluated as catalysts for the trichlorosilane mediated asymmetric hydrosilylation of ketimines. bis-Phosphine oxides, hydroxy-phosphine oxides, and biaryl phosphine oxides all demonstrated good catalytic activity, but poor to moderate enantioselectivity. A bis-P-chiral phosphine oxide displayed the highest enantioselectivity of 60%.
- Warner, Christopher J.A.,Berry, Sian S.,Jones, Simon
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- Kinetics and mechanistic investigation of epoxy-anhydride compositions cured with quaternary phosphonium salts as accelerators
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Mechanism and curing kinetics of bisphenol A epoxy resin-iso-methyltetrahydrophthalic anhydride compositions using quaternary phosphonium salts as accelerators were investigated by differential scanning calorimetry (DSC) and electrospray mass-spectrometry (ESI-MS). The DSC method was applied to investigate curing kinetics and apparent activation energy values for the overall curing process. The DSC results showed that some of the phosphonium salts lead to a lower activation energy, that means they are more effective accelerators for the curing of epoxy-anhydride systems. The mechanism of curing was studied by ESI-MS using the model reaction of epichlorohydrin (E) with phthalic anhydride (PA) in the presence of phosphonium salts or 2-methylimidazole. Products containing the alkyl moiety of the phosphonium salt in form of alkyl esters could be identified. This suggests that the phosphonium salts activate the anhydride by electrophilic attack.
- Amirova, Lyaysan R.,Burilov, Alexander R.,Amirova, Liliya M.,Bauer, Ingmar,Habicher, Wolf D.
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p. 1088 - 1097
(2016/03/12)
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- Synthesis and properties of new tetrachlorocobaltate (II) and tetrachloromanganate (II) anion salts with dicationic counterions
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New tetrachlorocobaltate (II) and tetrachloromanganate (II) ionic compounds containing various counterdications were synthesized and characterized. These salts are soluble in polar solvents such as methanol and water. Physical properties such as thermal stability, melting point, and magnetic susceptibility of these salts depend on the cation or anion structure. The thermal stability of the phosphinium or imidazolium based salts is higher than that of the pyridinium or triethylaminonium analogues. The melting point of these compounds is following the order of triphenylphosphinium > pyridinium > imidazolium dications, and symmetrical dicationic salts > unsymmetrical ones. The magnetic susceptibility (χMT values) of tetrachloromanganate (II) anions-based salts is higher than that of tetrachlorocobaltate (II) anions-based salts. These dicationic salts exhibit weak antiferromagnetic interactions and have higher magnetic susceptibility than that of the previously reported tetrachloromanganate (II) and tetrachlorocobaltate(II) salts with monocationic counterion.
- Chang, Jui-Cheng,Ho, Wen-Yueh,Sun, I-Wen,Chou, Yu-Kai,Hsieh, Hsin-Hsiu,Wu, Tzi-Yi
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experimental part
p. 497 - 507
(2011/03/21)
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- Synthesis and properties of new (μ-oxo)bis[trichloroferrate(III)] dianion salts incorporated with dicationic moiety
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New (μ-oxo)bis[trichloroferrate(III)] dianions-based ionic compounds that contain various counterdications were synthesized and characterized with regards to their crystal structures, thermal properties, and magnetic susceptibility. These salts are soluble in polar solvents such as methanol and water. The melting point of these compounds is affected by the dication following the order of triphenylphosphinium > pyridinium > imidazolium dications, and symmetrical dicationic salts > unsymmetrical ones. In these compounds, the trichloroferrate dianion exists in either a linear or a bent form, which is affected by the dications. Interestingly, the dicationic diferrate compounds show magnetic coupling constants fairly smaller than those reported in literature for diferrate salts in which monocations are the counterion. Furthermore, unlike the diferrate salts associated with separate monocations, the linear diferrate dicationic compounds show magnetic coupling constant lower than that of bent diferrate dicationic salts.
- Chang, Jui-Cheng,Ho, Wen-Yueh,Sun, I-Wen,Chou, Yu-Kai,Hsieh, Hsin-Hsiu,Wu, Tzi-Yi,Liang, Shih-Shin
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experimental part
p. 2976 - 2984
(2011/01/06)
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- Diferrocenyl molecular wires. the role of heteroatom linkers
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Diferrocenyl molecular "wires", in which two ferrocenes are linked by a conjugated chain, allowing the communication of redox information between the ferrocenes, are a versatile platform on which to investigate notions of molecular conductivity. In this paper, we examine the role of heteroatoms=including O, P, S, and Se, as well as C atoms in various oxidation states=separated from the ferrocenes by intervening double bonds which minimize any steric effects. Surprisingly, oxygen is a better electronic mediator than sulfur, a phenomenon we attribute to superior molecular orbital overlap. These fundamental studies on redox coupling will help to guide the design of efficient organic conductors for organic electronics.
- Li, Yu,Josowicz, Mira,Tolbert, Laren M.
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supporting information; experimental part
p. 10374 - 10382
(2010/09/06)
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- Carboxylic acids and derivatives thereof and pharmaceutical compositions containing them
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The present invention relates to a novel class of compounds for treating hyperlipidemia, obesity and impaired glucose tolerance/noninsulin dependent diabetes mellitus without adversely affecting energy metabolism, and pharmaceutical compositions comprising the aforementioned compounds for the treatment of obesity, hyperlipidemia and maturity-onset diabetes.
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- Understanding the structural properties of a homologous series of bis-diphenylphosphine oxides
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A homologous series of bis-diphenylphosphine oxides (C6H5)2PO-(CH2)nPO(C 6H5)2 (with n = 2-8; denoted 2-8] have been investigated to explore the effects of a range of competing and cooperative intermolecular and intramolecular interactions on the structural properties in the solid state. The important factors influencing the structural properties include intramolecular aspects such as the conformation of the aliphatic chain and the intramolecular interaction between the two P=O dipoles in the molecule, and intermolecular aspects such as long-range electrostatic interactions (dominated by the arrangement of the P=O dipoles), C-H ... O interactions, C-H ... π interactions and π ... π interactions. Compounds 3 and 5 could be crystallized only as solvate co-crystals (3 · water and 5 · (toluene)2], whereas the crystal structures of all the other compounds contain only the bis-diphenylphosphine oxide molecule. The crystal structures have been determined from single-crystal X-ray diffraction data, with the exception of 7 (which has been determined here from powder X-ray diffraction data) and 4 (which was known previously). The compounds with even n represent a systematic structural series, exhibiting characteristic, essentially linear P=O ... P=O ... P=O dipolar arrays, together with C-H ... O and C-H ... π interactions. For the compounds with odd n, on the other hand, uniform structural behaviour is not observed across the series, although certain aspects of these crystal structures contribute in a general sense to our understanding of the structural properties of bis-diphenylphosphine oxides. Importantly, for the compounds with odd n, there is "frustration" with regard to the molecular conformation, as the preferred all-anti conformation of the aliphatic chain gives rise to an unfavourable parallel alignment of the two P=O dipoles within the molecule. Clearly the importance of avoiding a parallel alignment of the P=O dipoles becomes greater as n decreases. Local structural aspects (investigated by high-resolution solid-state 31P NMR spectroscopy) and thermal properties of the bis-diphenylphosphine oxide materials are also reported.
- Calcagno, Patrizia,Kariuki, Benson M.,Kitchin, Simon J.,Robinson, James M. A.,Philp, Douglas,Harris, Kenneth D. M.
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p. 2338 - 2349
(2007/10/03)
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- Synthesis of 2-phenyl-2-cycloalkenones via palladium-catalyzed tandem epoxide isomerization-intramolecular aldol condensation
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We have extended the scope of our palladium-catalyzed tandem epoxide isomerization/aldol condensation reaction to encompass intramolecular condensations, which provide facile access to conjugated cycloalkenones from epoxy aldehydes or diepoxides. For example, reaction of 5,6-epoxy-6- phenylhexanal with Pd(OAc)2-PBu3 catalyst in the presence of NaHCO3 and 3A molecular sieves forms 2-phenyl-2-cyclopentenone (80%). Similarly, 1,2;5,6-diepoxy-1-phenylhexane affords 3-methyl-2-phenyl-2-cyclopentenone (72%). The observation of dicarbonyl intermediates (e.g., 1-phenyl-2,5- hexanedione in the latter case) demonstrates that the reaction proceeds via Pd-catalyzed isomerization of the diepoxide to the diketone, followed by base-catalyzed aldol condensation.
- Kim, Ji-Hyun,Kulawiec, Robert J.
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p. 3107 - 3110
(2007/10/03)
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- THERMAL CONVERSION OF 1,5,9-TRIYNES. CYCLOADDITIONS OR SIGMATROPIC SHIFTS?
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The gas phase pyrolyses of variously labeled 1,5,9-decatriynes (1) and 1,5,9-cyclododecatriynes (2) were investigated to determine possible modes of thermal isomerizations.Conditions included temperatures in the range 400-600 deg C, pressures of 40 -10E-4 Torr, and contact times of ca 1 ms to 15 s.The labeling patterns in 1 and 2 were chosen such as to be able to distinguish direct intramolecular cycloadditions of the alkyne units to form an aromatic ring (perhaps with subsequent rearrangements), and sigmatropic shifts of the 1,5-diyne moieties.Methods for synthesizing the isotopically (particularly (13)C) labeled triynes were devised and implemented.The route to 5,6-(13)C2-1,5,9-decatriyne (1c) made use of a new procedure for the synthesis of symmetrically disubstituted alkynes involving coupling between two equivalents of an alkyl copper reagent and diiodoacetylene-(13)C2.The synthesis of 1,10-(13)C2-1,5,9-cyclododecatriyne (2b) was accomplished starting with K(13)CN, elaboration to labeled diethyl succinate, a crucial bis-Wittig condensation to labeled 1,5,9-cyclododecatriene 10, and bromination-dehydrobromination of the latter (NaOH-ethylene glycol).Products from the pyrolysis of unlabeled 1a included dicyclobutabenzene, naphtalene and 3,4-dimethylidene-1-(but-3-ynyl)cyclobutene.Pyrolysis of 1b gave 3,6-dideuteriodicyclobutabenzene and partially deuterated naphthalene, that of 1c produced 1,2-(13)C2-dicyclobutabenzene and 9,10-(13)C2-naphthalene.While the pyrolysis of 2a resulted in hexamethylidenecyclohexane (hexaradialene), 2b furnished 1,4-(13)C2-hexaradialene.The results rule out the occurence of cycloadditions of the alkyne units, but are consistent with the intervention of a series sigmatropic shifts which connect starting materials with products.
- Dower, William V.,Vollhardt, K. Peter C.
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p. 1873 - 1882
(2007/10/02)
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