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101.
J. Sanmartín M. R. Bermejo J. A. García-Vázquez J. Romero A. Sousa 《Transition Metal Chemistry》1993,18(5):528-530
Summary The electrochemical oxidation of anodic metals (iron and copper) in MeCN solutions of 2-pyridinone (HOPy), 1-hydroxy-2-pyridinethione (HPT), 2-pyridinemethanethiol-1-oxide (HPMTO) or its dimer 2,2-dithiodimethyldipyridine-1,1-dioxide (PMTO)2, gave the simple complexes Fe(OPy)2 · H2O, Cu(OPy)2 · 3H2O, Fe(PT)2 · 3H2O, Fe(PT)3, Cu(PT)2, Fe(PMTO)2·3H2O and Cu(PMTO)2·H2O, respectively. When 1,10-phenanthroline (phen) was added to the electrolytic phase, only two mixed complexes were obtained: Cu(OPy)2phen·3H2O and Fe(PT)2phen·2H2O. The possible molecular structures of the complexes were studied on the basis of their i.r. spectra and magnetic properties. 相似文献
102.
Ana B. Gaspar 《Coordination chemistry reviews》2005,249(23):2661-2676
One of the most important trends in the spin crossover (SCO) field is focused on the synthesis of new molecule-based functional materials in which the SCO properties may be combined with other physical or chemical properties in a synergic fashion. The current stage of investigations regarding interplay and synergic effects between SCO, magnetic coupling, liquid crystalline properties, host-guest interactions, non-linear optical properties, electrical conductivity, and ligand isomerization is highlighted and discussed. 相似文献
103.
Die erste Röntgenstrukturanalyse eines 3,7-Dehydrotropon ( 1 )-Derivates, nämlich von 2-Diisopropylammo-3,7-dehydrotropon ( 4 ) zeigt das Ringsystem in 4 als planaren Bicyclus mit nahezu C2V-Symmetrie. Dementsprechend enthalten Dehydrotropone formell zwei trans-konfigurierte Doppelbindungen in einem 7-gliedrigen Ring; auch das O-Atom und das N-Atom mit seinen Ligandatomen liegen in derselben Ebene wie die Ringatome. Die Bindung zwischen den beiden C-Atomen, welche die Heteroatome tragen, (C(1) and C(2)), ist wesentlich langer (1,56 Å) als die anderen Bindungen im Ringsystem (1,37-1,46 Å). Dies impliziert eine ‘push-pull’-π-Elektronen-Delokalisierung, in der auch das O-und das N-Atom involviert sind, und macht eine ‘aromatische’ Ring-Delokalisierung weniger wahr-scheinlich. Im Gegensatz zu 2-(t-Butyl)-3,7-dehydrotropon ( 3 ) existiert das 2-Diiso-propylamino-3,7-dehydrotropon ( 4 ) im Kristall als Monomeres, was dem stabili-sierenden Einfluss der ‘push-pull’-Delokausierung zugeschrieben werden kann. 相似文献
104.
Rodrigues JA Abramovitch RA de Sousa JD Leiva GC 《The Journal of organic chemistry》2004,69(9):2920-2928
In preliminary communications, we reported the diastereoselective synthesis of cularine and sarcocapnine via the intramolecular ring closure of nitrenium and oxenium ions, a new highly diastereoselective reductive methylation with (+)-8-phenylmenthyl chloroacetate followed by reduction with sodium borohydride, and a facile entry to the isoquinoline precursors by aza-Wittig electrocyclic ring closure. We now report the full details of the syntheses of (+)-O-demethylcularine, (+)-cularine, (+)-sarcocapnidine, (+)-sarcocapnine, and (+)-crassifoline and describe different methods of synthesis of their precursors. 相似文献
105.
Maurício Cavicchioli Antonio Carlos Massabni Luciana Rebelo Guilherme Eduardo Ernesto Castellano Armando Paduan-Filho Ana Maria da Costa Ferreira 《Transition Metal Chemistry》2007,32(3):355-361
Structural, electrochemical and spectroscopic data of a new dinuclear copper(II) complex with (±)-2-(p-methoxyphenoxy)propionic acid are reported. The complex {tetra-μ-[(±)-2-(p-methoxyphenoxy)propionato-O,O′]-bis(aqua)dicopper(II)} crystallizes in the monoclinic system, space group P21/n with a = 14.149(1) ?, b = 7.495(1) ?, c = 19.827(1) ?, β = 90.62(1) and Z = 4. X-ray diffraction data show that the two copper(II) ions are held together through four carboxylate bridges, coordinated
as equatorial ligands in square pyramidal geometry. The coordination sphere around each copper ion is completed by two water
molecules as axial ligands. Thermogravimetric data are consistent with such results. The ligand has an “L” type shape due
to the angle formed by the β-carbon of the propionic chain and the linked p-methoxyphenoxy group. This conformation contributes to the occurrence of a peculiar structure of the complex. The complex
retains its dinuclear nature when dissolved in acetonitrile, but it decomposes into the corresponding mononuclear species
if dissolved in ethanol, according to the EPR measurements. Further, cyclic voltammograms of the complex in acetonitrile show
that the dinuclear species maintains the same structure, in agreement with the EPR data in this solvent. The voltammogram
shows two irreversible reduction waves at E
pc = −0.73 and −1.04 V vs. Ag/AgCl assigned to the Cu(II)/Cu(I) and Cu(I)/Cu° redox couples, respectively, and two successive oxidation waves at E
pa =− 0.01 and +1.41 V vs. Ag/AgCl, assigned to the Cu°/Cu(I) and Cu(I)/Cu(II) redox couples, respectively, in addition to the oxidation waves of the
carboxylate ligand. 相似文献
106.
Wolfgang Stadlbauer Rita Laschober Thomas Kappe 《Monatshefte für Chemie / Chemical Monthly》1991,122(10):853-861
Summary 4-Chloro-3-aryl-coumarins and quinolones2 a–e undergo thermolytic ring closure by reaction with sodium azide in refluxing dimethyl formamide to yield indolo[3,2-c]coumarins and indolo[3,2-c]quinolin-6(5H)-ones6 a–e. In the case of the coumarin2 a the azido coumarin5 can be isolated. The mono- and diazacoumestrol-dimethylethers6 a–c are converted into the coumestrol analogues7 a–c and their diacetyl derivatives8 a–c.
Potentielle nichtsteroidale Östrogene und Antiöstrogene, 4. Mitt.: Organische Azide in der Heterocyclensynthese, Teil 13: Synthese von Aza- und Diazacumöstrolen über Azidzwischenstufen
Zusammenfassung 4-Chlor-3-arylcumarine und-chinolone2 a–e reagieren thermolytisch mit Natriumazid in siedendem Dimethylfomamid unter Ringschluß zu Indolo[3,2-c]cumarinen und Indolo[3,2-c]chinolin-6(5H)-onen6 a–e. Nur aus dem Cumarinderivat2 a kann das zwischenzeitlich gebildete Azidocumarin5 isoliert werden. Die so erhaltenen Mono- und Diazacumöstroldimethylether6 a–c werden in die entsprechenden Cumöstrole7 a–c und ihre Diacetylderivate8 a–c umgewandelt.相似文献
107.
A new computationally-assisted methodology (PiMM), which accounts for the effects of intermolecular interactions in the crystal, is applied to the complete assignment of the Raman and infrared vibrational spectra of room temperature forms of crystalline caffeine, theobromine, and theophylline. The vibrational shifts due to crystal packing interactions are evaluated from ab initio calculations for a set of suitable molecular pairs, using the B3LYP/6-31G* approach.The proposed methodology provides an answer to the current demand for a reliable assignment of the vibrational spectra of these methyl-xanthines, and clarifies several misleading assignments. The most relevant intermolecular interactions in each system and their effect on the vibrational spectra are considered and discussed. Based on these results, significant insights are obtained for the structure of caffeine in the anhydrous form (stable at room temperature), for which no X-ray structure has been reported. A possible structure based on C((8))--H...N((9)) and C((1,3))--H...O intermolecular interactions is suggested. 相似文献
108.
Erik G.P. da Silva Ana Carolina do N. Santos Antnio C.S. Costa Dalva M. da N. Fortunato Ndia M. Jos Maria G.A. Korn Walter N.L. dos Santos Srgio L.C. Ferreira 《Microchemical Journal》2006,82(2):159-162
In the present work, a slurry sampling flame atomic absorption spectrometric method to determine directly manganese and zinc in powdered chocolate samples is proposed. The optimization step was performed using univariate methodology involving the following factors: nature and concentration of the acid solution, sonication time, and particle size. The established conditions led to the use of a sample mass of 150 mg, 2.0 mol L− 1 nitric acid solution, sonication time of 15 min, and a slurry volume of 50 mL. This method allows the determination of manganese and zinc with detection limit of 52 and 61 ng g− 1, respectively, and a precision expressed as relative standard deviation (RSD) of 2.6% and 3.2% (both, n = 10) for contents of manganese and zinc of 52.4 and 100.0 μg g− 1, respectively. The proposed method was applied for determination of manganese and zinc in five powdered chocolate samples. In these, the manganese content varied from 42.8 to 52.7 and from 88.6 to 102.4 μg g− 1 of zinc. The analytical results were compared with the results obtained by analysis of these samples after digestion using open vessel and acid bomb digestion procedures and determination using FS-FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results. 相似文献
109.
Abdelhak Benabra Ana Alcudia Noureddine Khiar Inmaculada Fernández Felipe Alcudia 《Tetrahedron: Asymmetry》1996,7(12):3353-3356
The stereochemical outcome of the reaction of chiral secondary alcohols with a phosphinyl chloride was found to be highly dependent on the achiral base used. Thus, the reaction of the readily available sugar derived carbinols, 1 and 2, with methylphenylphosphinyl chloride in the presence of triethylamine yields stereoselectively the corresponding Snp-phosphinates 3Sp and 5Sp in 94 and 92% diastereomeric excess (de). Simply changing the base from triethylamine to pyridine affords Rp-phosphinates 4Rp and 6Rp epimers to 3Sp and 5Sp at the phosphinyl phosphorus in 50 and 40% de respectively. These phosphinate esters were found to be good P-chiral transferring intermediates, they react with Grignard reagents under very mild conditions to give the corresponding phosphine oxides. Both enantiomers Sp- and Rp-o-anisylmethylphenylphosphine oxide (PAMPO) as well Sp- and Rp- methylphenylpropyl phosphine oxide were obained enantiomerically pure in high yields 相似文献
110.
Ana M. Gómez Ana PedregosaSeraf?&#x;n Valverde J.Cristóbal López 《Tetrahedron letters》2003,44(32):6111-6116
Halo-exo-glycals of the gluco-, manno- and galacto- series, readily prepared by reaction of 1-exo-methylene pyranoses with iodonium dicollidinium triflate (IDCT), undergo Suzuki or B-alkyl Suzuki cross-coupling reactions with boronic acids or alkyl boranes to yield, in a stereoselective manner, functionalized exo-glycals. 相似文献