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991.
The reaction of readily accessible 1,1-dialkylhydrazones with commercially available o-(trimethylsilyl)aryl triflates provides a direct one-step route to pharmaceutically important 1-alkylindazoles. The products are obtained in high yields by one-pot NCS-chlorination/aryne annulation or Ac(2)O-acylation/deprotection/aromatization protocols. 相似文献
992.
A novel thermal rearrangement, involving pyrimidine ring opening and subsequent ring closure leading to recyclization of the system, was identified in the reaction of (6-oxo-1,6-dihydropyrimidin-2-yl)guanidines 3 (where NR(1)R(2) = NH(2), NH alkyl, NH aralkyl, NHCH(2)Ph(R)) with triethyl orthoacetate, affording 4-substituted-2-methyl-6H-pyrimido[1,2-a][1,3,5]triazin-6-ones 6 and their ring opened products. However, no such rearrangement was observed with (6-oxo-1,6-dihydropyrimidin-2-yl)guanidines 3 bearing a tertiary amino or anilino substituent (i.e. where NR(1)R(2) = N(CH(3))(2), indoline, morpholino, NHAr). As expected, 2-substituted-4-methyl-6H-pyrimido[1,2-a][1,3,5]triazin-6-ones 4 were obtained as the final products. Experimental structural determination and theoretical studies were carried out to get an understanding of the observed thermal rearrangement. In addition, an attempt to obtain similar pyrimido[1,2-a][1,3,5]triazin-6-ones using N,N-dimethylacetamide dimethyl acetal (DMA-DMA) as one carbon inserting synthon had furnished triazine ring annulated product 14 bearing N,N-dimethyl enamino substituent at position 4 as a result of further reaction with a second molecule of DMA-DMA. 相似文献
993.
H Degenbeck AS Felten EC Escudero-Adán J Benet-Buchholz L Di Bari G Pescitelli A Vidal-Ferran 《Inorganic chemistry》2012,51(16):8643-8645
We describe an efficient methodology for the preparation of new chiral zinc complexes by assembling dynamically racemic biphenol derivatives and chiral 1,2-diamines with suitable zinc(II) precursors. Mononuclear and dinuclear zinc(II) complexes were formed from differently substituted biphenols. The solid-state and solution structural characterization of the resulting compounds allowed us to demonstrate a preferential sense of induced axial chirality for mononuclear complexes, a phenomenon that was not observed for the dinuclear ones. 相似文献
994.
Ondřej Rudolf Vladimír Mrkvička Antonín Lyčka Michal Rouchal Antonín Klásek 《Helvetica chimica acta》2012,95(8):1352-1372
The Riemschneider reaction of 3‐thiocyanatoquinoline‐2,4(1H,3H)‐diones with conc. H2SO4 was investigated. Using different reaction conditions, 13 types of reaction products were isolated. Compounds bearing a Me, Et, or Bu group at C(3) afforded mainly [1,3]thiazolo[5,4‐c]quinoline‐2,4‐diones and 1,9b‐dihydro‐9b‐hydroxythiazolo[5,4‐c]quinoline‐2,4‐diones. In the case of the 3‐Bu derivatives of the starting compounds, C‐debutylation was also observed. If a Bn group is present at C(3), rapid C‐debenzylation of the starting thiocyanates occurred, yielding [1,3]oxathiolo[4,5‐c]quinoline‐2,4‐diones, and mixtures of mono‐, di‐, and trisulfides derived from 4‐hydroxy‐3‐sulfanylquinoline‐2‐ones. The reaction mechanism of all of the transformations is discussed. All new compounds were characterized by IR, 1H‐ and 13C‐NMR, and EI and ESI mass spectra, and in some cases, 15N‐NMR spectra were also used to characterize new compounds. 相似文献
995.
A new multiscale modeling method for simulating the loss processes in polymer solar cell nanodevices
The photoelectric power conversion efficiency of polymer solar cells is till now, compared to conventional inorganic solar cells, still relatively low with maximum values ranging from 7% to 8%. This essentially relates to the existence of exciton and charge carrier loss phenomena, reducing the performance of polymer solar cells significantly. In this paper we introduce a new computer simulation technique, which permits to explore the causes of the occurrence of such phenomena at the nanoscale and to design new photovoltaic materials with optimized opto-electronic properties. Our approach consists in coupling a mesoscopic field-theoretic method with a suitable dynamic Monte Carlo algorithm, to model the elementary photovoltaic processes. Using this algorithm, we investigate the influence of structural characteristics and different device conditions on the exciton generation and charge transport efficiencies in case of a novel nanostructured polymer blend. More specifically, we find that the disjunction of continuous percolation paths leads to the creation of dead ends, resulting in charge carrier losses through charge recombination. Moreover, we observe that defects are characterized by a low exciton dissociation efficiency due to a high charge accumulation, counteracting the charge generation process. From these observations, we conclude that both the charge carrier loss and the exciton loss phenomena lead to a dramatic decrease in the internal quantum efficiency. Finally, by analyzing the photovoltaic behavior of the nanostructures under different circuit conditions, we demonstrate that charge injection significantly determines the impact of the defects on the solar cell performance. 相似文献
996.
Šimon P Jambor R Růžička A Lyčka A De Proft F Dostál L 《Dalton transactions (Cambridge, England : 2003)》2012,41(17):5140-5143
NCN chelated monomeric chalcogenides, LSbE (E = S (1), Se (2), L = 2,6-bis[N-(2',6'-dimethylphenyl)ketimino]phenyl), were synthesized and characterized with the help of elemental analysis, NMR spectroscopy and single-crystal X-ray diffraction analyses. The terminal Sb-E (E = S, Se) bonds in 1 and 2 were subjected to theoretical investigation and the results are compared with the hypothetical molecules, PhSb=E (E = S, Se, Te), and earlier reported analogues. 相似文献
997.
Christian Brackmann Anton Bengtsson Marie Larsson Alminger Ulf Svanberg Annika Enejder 《Journal of Raman spectroscopy : JRS》2011,42(4):586-592
Information on the content and bioavailability of provitamin A carotenoids, such as β‐carotene, in plant foods is of great interest due to the widespread vitamin A deficiency in developing countries. While the amount of β‐carotene can readily be quantified with analytical techniques, there is limited information on β‐carotene morphology in native plant materials. Here, we introduce nonlinear microscopy for three‐dimensional, label‐free imaging of carotenoids in fresh and thermally treated plant tissues, providing quantitative information at single‐aggregate level and detailed insight into their distribution. Carotenoids in orange‐fleshed sweet potato (OFSP), carrot, and mango were visualized by coherent anti‐Stokes Raman scattering (CARS) microscopy and, in the case of OFSP, related to the plant‐matrix morphology by simultaneous second‐harmonic generation (SHG) microscopy of starch granules. Sizes, shapes, densities, and location of different types of carotenoid bodies were quantified. While OFSP and carrot showed heterogeneous rod‐shaped bodies with high carotenoid densities indicated by higher CARS signals, the carotenoid‐filled lipid droplets in mango appeared as homogeneous low‐density aggregates of rounded shape. In addition, β‐carotene densities and morphologies in OFSP were studied after thermal processing, showing that the bodies remain intact despite significant changes of the surrounding starch granules. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
998.
Anton Kiriy Volodymyr Senkovskyy Michael Sommer 《Macromolecular rapid communications》2011,32(19):1503-1517
Kumada catalyst‐transfer polycondensation (KCTP) is a new but rapidly developing method with great potential for the preparation of well‐defined conjugated polymers (CPs). The recently discovered chain‐growth mechanism is unique among the various transition metal‐catalyzed polycondensations, and has thus attracted much attention among researchers. Most progress is found in the areas of mechanism and external initiation via new initiators, but also the number of monomers other than thiophene that can be polymerized is steadily increasing. Accordingly, the variety of CP chain architectures is increasing as well, and a considerable contribution of KCTP toward more efficient materials can be expected in the future. This review critically focuses on very recent progress in the synthesis of CPs and the mechanism of KCTP, and is finally aimed at providing a comprehensive picture of this exciting polymerization method.
999.
Michal Ilavsk Karel Bouchal Helena Valentovä František Lednick Antonín Sikora Josef Baldrian 《Journal of Macromolecular Science: Physics》2013,52(5):645-666
Synthesis of the liquid crystalline (LC) diol 6,6′-[ethylenebis(l,4-phenylene-oxy)]-dihexanol (I) is described. The structure of polyurethanes prepared from diol I and 4,4′-methylenedi(phenyl isocyanate) (MDI), 4,4′-methylenedi(cyclohexyl isocyanate) (HMDI), or 2(4)-methyl-l,3-phenylene diisocyanate (TDI) at 1:1 molar ratios of isocyanate and hydroxy groups is studied by dynamic mechanical spectroscopy, differential scanning calorimetry (DSC), polarizing microscopy, and x-ray scattering. The polymer prepared from HMDI and the diol (I/HMDI) shows, on cooling, thermal behavior typical of amorphous polymers. A frequency-temperature superposition could be applied to the mechanical data, and the horizontal shift factor satisfied the Williams-Landel-Ferry (WLF) equation. A more-complex thermal behavior was found for I/HMDI polymer during subsequent heating; above 70°C, the formation of an ordered structure takes place, and this structure melts at about 120°C. Complex thermal behavior is exhibited by I/TDI polymer. On cooling its melt, the polymer forms a nematic phase at about 80°C, which freezes into the LC glassy state. On heating, the mesophase melts, and. subsequently, a better-ordered smectic phase is formed at 95°C, which melts at 120°C. This structure buildup is accompanied by a rapid increase in storage modulus G′, and the sample shows thermorheologically complex mechanical behavior. The polymer formed from the diol and MDI (I/MDI) exhibits a most-complex thermal behavior. On cooling and heating, four transitions can be detected in its thermal mechanical behavior, and the structure of the polymer is strongly dependent on its thermal history. 相似文献
1000.
La2+xMnGe2+y (I) and Ce2+xMnGe2+y (II) are prepared by arc‐melting of the elements in molar ratios of 2:1:2 followed by annealing (sealed silica tubes, 800 °C, 2 weeks). 相似文献