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991.
Gutiérrez MM Amorebieta VT Estiú GL Olabe JA 《Journal of the American Chemical Society》2002,124(35):10307-10319
The electrophilic reactivity of the pentacyanonitrosylferrate(II) ion, [Fe(CN)(5)NO](2)(-), toward hydrazine (Hz) and substituted hydrazines (MeHz, 1,1-Me(2)Hz, and 1,2-Me(2)Hz) has been studied by means of stoichiometric and kinetic experiments (pH 6-10). The reaction of Hz led to N(2)O and NH(3), with similar paths for MeHz and 1,1-Me(2)Hz, which form the corresponding amines. A parallel path has been found for MeHz, leading to N(2)O, N(2), and MeOH. The reaction of 1,2-Me(2)Hz follows a different route, characterized by azomethane formation (MeNNMe), full reduction of nitrosyl to NH(3), and intermediate detection of [Fe(CN)(5)NO](3)(-). In the above reactions, [Fe(CN)(5)H(2)O](3)(-) was always a product, allowing the system to proceed catalytically for nitrite reduction, an issue relevant in relation to the behavior of the nitrite and nitric oxide reductase enzymes. The mechanism comprises initial reversible adduct formation through the binding of the nucleophile to the N-atom of nitrosyl. The adducts decompose through OH(-) attack giving the final products, without intermediate detection. Rate constants for the adduct-formation steps (k = 0.43 M(-)(1) s(-)(1), 25 degrees C for Hz) decrease with methylation by about an order of magnitude. Among the different systems studied, one-, two-, and multielectron reductions of bound NO(+) are analyzed comparatively, with consideration of the role of NO, HNO (nitroxyl), and hydroxylamine as bound intermediates. A DFT study (B3LYP) of the reaction profile allows one to characterize intermediates in the potential hypersurface. These are the initial adducts, as well as their decomposition products, the eta(1)- and eta(2)-linkage isomers of N(2)O. 相似文献
992.
The synthesis of compound 12 which has a hexahydro‐1,5‐methanoazocino[4,3‐b]indole structure for the synthesis of pentacyclic strychnos type alkaloids (tubifolin and tubifolidine) is described. Many new compounds 5–12 have also been synthesized. 相似文献
993.
The synthesis of liquid single crystal hydrogels (“LSCH”) in suitable molds offers an innovative concept to realize bifocal contact‐ or intraocular‐lenses. LSCH combine the properties required for applications as bifocal ophthalmic lenses: the soft and water‐containing hydrogel enables oxygen permeation and exhibits high birefringence due to the liquid crystalline phase structure built up by rigid rod‐like amphiphiles. Via a photo‐initiated crosslinking reaction of aqueous solutions of monomeric lyotropic liquid crystalline amphiphiles in the macroscopically ordered liquid crystalline state, we obtain optically uniaxially ordered and transparent LSCH. The orientation process and the phase structure of the anisotropic hydrogel is analyzed by deuterium NMR‐spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
994.
Alvaro M Formentín P García H Palomares E Sabater MJ 《The Journal of organic chemistry》2002,67(15):5184-5189
Three N-alkylpyridinium photosensitizers having chiral alkyl groups have been prepared by reacting 2,4,6-triphenylpyrylium tetrafluoroborate ion with (1R,2S)-(-)-norephedrine, (S)-(+)-2-(aminomethyl)pyrrolidine, and (R)-(-)-1-cyclohexylethylamine. Laser flash photolysis allows detection of the corresponding triplet excited states that are quenched by hydrogen atom donors and electron donors. Asymmetric quenching of the chiral triplet excited state was observed using enantiomerically pure 1,2-diamino cyclohexane as quencher. Low enantiomeric excess values (up to 7%) were measured for the photochemical cyclization of 5-methyl-4-hexenoic acid to its corresponding gamma-lactone using these chiral N-alkylpyridinium as photosensitizers. 相似文献
995.
Vera L.M. Silva Artur M.S. Silva Rosa M. Claramunt Concepción López Dionisia Sanz Lourdes Infantes Ángela Martínez López Felipe Reviriego Ibon Alkorta José Elguero 《Tetrahedron》2019,75(48):130690
Tetrakis(1H-pyrazol-1-yl)methanes are very rare compounds of which only two are known: the unsubstituted 1 obtained classically by Hückel in 1937 from carbon tetrachloride and prepared again several times and the 3,5-dimethyl substituted 2 obtained serendipitously by Pombeiro in 2009. We have now extended this group to include four new derivatives 8, 9, 11 and 12 bearing methyl groups. The X-ray crystal structure of the four compounds has been determined. They have been studied by NMR both in solution (1H, 13C, 15N) and in the solid state (13C and 15N). DFT calculations of the six compounds (geometries, energies and absolute shieldings) have been used to discuss the experimental observations. 相似文献
996.
N‐coordinate Pd2+ complexes [PdL2] (L: N‐N‐quinoline‐8‐yl‐R‐benzenesulfonamides) ( 6–10 ) and [PdL2] complexes assembled on multi‐wall carbon nanotubes (MWCNTs) hybrid nanomaterials were fabricated and characterized by various techniques. The [PdL2] impregnated MWCNTs materials ( 11–15 ) were applied as a counter electrode (CE) catalyst for triiodide to iodide reduction reaction in the dye‐sensitized solar cells (DSSC) and investigated electro‐catalytic activities. The MWCNTs‐supported [PdL2] CEs ( 11–15 ) are exhibits as Pt‐free CE with good power conversion efficiencies (PCEs), and compared to platinum and bare MWCNTs CEs and the PCE of bare MWCNTs was clearly improved by means of [PdL2] complexes ( 6–10 ). The DSSCs based on the hybrid counter electrodes (CEs) ( 11–15 ) and bare MWCNTs are indicated a relative efficiency ( ? rel ) of 64.27%, 54.07%, 53.75%, 51.52% 44.82% and 27.27% concerning a Pt CE control device set at 100%. The report emphasizes that [PdL2] impregnated MWCNTs type counter electrodes (CEs) ( 11–15 ) are promising as effectively catalyst in working device design, particularly taking into account the eco‐friendly approach of the hybrids. 相似文献
997.
Hasan Kırmızıbekmez Yiğit İnan Rengin Reis Hande Sipahi Ahmet C. Gören Erdem Yeşilada 《Natural product research》2019,33(17):2541-2544
Phytochemical investigations on the EtOH extract of Clematis viticella led to the isolation of six flavonoid glycosides, isoorientin (1), isoorientin 3′-O-methyl ether (2), quercetin 7-O-α-L-rhamnopyranoside (3), quercetin 3,7-di-O-α-L-rhamnopyranoside (4), manghaslin (5) and chrysoeriol 7-O-β-D-glucopyranoside (6), one phenylethanol derivative, hydroxytyrosol (7), along with three phenolic acids, caffeic acid (8), (E)-p-coumaric acid (9) and p-hydroxybenzoic acid (10). The structures of the isolates were elucidated on the basis of NMR and HR-MS data. All compounds were isolated from C. viticella for the first time. Compounds 7 and 8 showed significant anti-inflammatory activity at 100 μM by reducing the release of NO in LPS-stimulated macrophages comparable to positive control indomethacin. Compounds 3 and 7 exhibited anti-inflammatory activity through lowering the levels of TNF-α while 1, 3 and 5 decreased the levels of neopterin better than the positive controls. 相似文献
998.
Iván Montenegro 《Natural product research》2019,33(8):1214-1217
A series of novel dihydrochalcone derivatives 2–7 were synthesized from dihydroisorcordoin 1 which was isolated from the aerial parts of Adesmia balsamica. The structures of all compounds were confirmed by 1H NMR, 13C NMR, and HRMS. Their anti-oomycete activity was evaluated in vitro against Saprolegnia parasitica and Saprolegnia diclina. Some of the newly synthesized compounds exhibited better anti-oomycete activities at low values compared with bronopol and fluconazole as positive controls. Among them, compound 7 exhibited strong activity, with minimum inhibitory concentration and minimum oomyceticidal concentration values of 75 and 100 μg/mL, respectively. 相似文献
999.
Xi‐Jie Dai Oliver D. Engl Thierry Len Stephen L. Buchwald 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3445-3449
Herein, we report a practical two‐step synthetic route to α‐arylpyrrolidines through Suzuki–Miyaura cross‐coupling and enantioselective copper‐catalyzed intramolecular hydroamination reactions. The excellent stereoselectivity and broad scope for the transformation of substrates with pharmaceutically relevant heteroarenes render this method a practical and versatile approach for pyrrolidine synthesis. Additionally, this intramolecular hydroamination strategy facilitates the asymmetric synthesis of tetrahydroisoquinolines and medium‐ring dibenzo‐fused nitrogen heterocycles. 相似文献
1000.
Titas Braukyla Rui Xia Maryte Daskeviciene Tadas Malinauskas Alytis Gruodis Vygintas Jankauskas Zhaofu Fei Cristina Momblona Cristina Roldn‐Carmona Paul J. Dyson Vytautas Getautis Mohammad Khaja Nazeeruddin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11388-11394
The synthesis of three enamine hole‐transporting materials (HTMs) based on Tröger's base scaffold are reported. These compounds are obtained in a three‐step facile synthesis from commercially available materials without the need of expensive catalysts, inert conditions or time‐consuming purification steps. The best performing material, HTM3, demonstrated 18.62 % PCE in PSCs, rivaling spiro‐OMeTAD in efficiency, and showing markedly superior long‐term stability in non‐encapsulated devices. In dopant‐free PSCs, HTM3 outperformed spiro‐OMeTAD by a factror of 1.6. The high glass‐transition temperature (Tg=176 °C) of HTM3 also suggests promising perspectives in device applications. 相似文献