共查询到20条相似文献,搜索用时 31 毫秒
1.
Wei DENG Ye Feng WANG Chen ZHANG Lei LIU Qing Xiang GUO 《中国化学快报》2006,17(3):313-316
Qing Xiang GUON-Arylated heterocycles such as pyrroles, indoles, and imidazoles are important building blocks for the synthesis of natural products, pharmaceuticals, and function materials1. Usually these compounds were synthesized by Cu-catalyzed Ullmann… 相似文献
2.
Cation-π interactions have been widely exploited and utilised in the structural biology arena, their fundamental importance in supramolecular chemistry and the pivotal role they play in host guest chemistry has rapidly expanded. In terms of organic synthesis π-π, CH-π and cation-π interactions are often invoked providing hypotheses for observed selectivities and reaction outcomes although fundamental studies of these interactions are less well reported, especially in the organic synthesis arena. This article considers cation-π interactions in the field of asymmetric organocatalysis and provides a summary of cases where such interactions may play an important role. Importantly this article sets out to highlight where such interactions could be operating in order to highlight the potential wealth of investigations to be had in this area rather than categorically claiming such interactions are in operation. For asymmetric catalysis this is particularly important as the geometry of a transition state dictates the stereochemical outcome of the reaction, this article provides a perspective on such phenomena. 相似文献
3.
Nan Zhang Dr. Leigang Li Juan Wang Dr. Zhiwei Hu Dr. Qi Shao Prof. Xiangheng Xiao Prof. Xiaoqing Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8143-8148
Surface regulation is an effective strategy to improve the performance of catalysts, but it has been rarely demonstrated for nitrogen reduction reaction (NRR) to date. Now, surface-rough Rh2Sb nanorod (RNR) and surface-smooth Rh2Sb NR (SNR) were selectively created, and their performance for NRR was investigated. The high-index-facet bounded Rh2Sb RNRs/C exhibit a high NH3 yield rate of 228.85±12.96 μg h−1 mg−1Rh at −0.45 V versus reversible hydrogen electrode (RHE), outperforming the Rh2Sb SNRs/C (63.07±4.45 μg h−1 mg−1Rh) and Rh nanoparticles/C (22.82±1.49 μg h−1 mg−1Rh), owing to the enhanced adsorption and activation of N2 on high-index facets. Rh2Sb RNRs/C also show durable stability with negligible activity decay after 10 h of successive electrolysis. The present work demonstrates that surface regulation plays an important role in promoting NRR activity and provides a new strategy for creating efficient NRR electrocatalysts. 相似文献
4.
ARMSTRONG Alan EDMONDS Ian COOKE Richard S. SHANAHAN Stephen E. KNIGHT Jamie D. CUMMING Graham R. 《中国化学》2005,23(9):1270-1272
Structure/reactivity relationships of N-alkoxycarbonyl- and N-carboxamidooxaziridines are explored, and conditions are discovered for the efficient amination of sulfides and primary amines. Reactions of these oxaziridines with alkenes are also examined, and lead to interesting new heteroatom transfer reaction products. Finally, the aminative rearrangement of 2-alkoxydihydropyrans leads to a useful stereocontrolled synthesis of pyrrolidines which can undergo synthetic manipulations to give [2.2.1]- and [3.2.1]-azabicycles. 相似文献
5.
LIU Tie-mei WANG Shu-sheng ZHU Guang-ze LI Ming-yang ZHANG Li-ping 《高等学校化学研究》2007,23(3):300-302
Antibody-directed enzyme prodrug therapy(ADEPT) is a new strategy for the treatment of cancer that has arisen in recent twenty years, the main merits of which are that it can improve the selectivity of anticancer drugs and reduce the side effects in remote tissue. In the present study, two prodrugs-glycosylated aromatic nitrogen mustard derivatives were synthesized. Glucose and lactose were converted into glycosyl donors-trichloroacetimidate; the obtained glycosyl donors were glycosylated with p-nitrophenol(glycosyl donors) to form β-glucosyl p-nitrobenzene and β-lactosyl p-nitrobenzene that were protected by acetyl in a stereoselective manner; the two products were reduced by zinc dust and then treated with ethylene oxide, afforded two glycosylated nitrogen mustard derivatives that were protected by acetyl; the last step was to deacetylate and then afforded the two target compounds that could be used as prodrugs of ADEPT for further Anti-tumor research. 相似文献
6.
Dr. Vladimir Y. Mikshiev Prof. Dr. Alexander F. Pozharskii Prof. Dr. Alexander Filarowski Dr. Alexander S. Novikov Dr. Alexander S. Antonov Prof. Dr. Peter M. Tolstoy Mikhail A. Vovk Olesya V. Khoroshilova 《Chemphyschem》2020,21(7):651-658
The protonation of the carboxamide nitrogen atom is an essential part of in vivo and in vitro processes (cis-trans isomerization, amides hydrolysis etc). This phenomenon is well studied in geometrically strongly distorted amides, although there is little data concerning the protonation of undistorted amides. In the latter case, the participation of amide nitrogen in hydrogen bonding (which can be regarded as the incipient state of a proton transfer process) is less well-studied. Thus, it would be a worthy goal to investigate the enthalpy of this interaction. We prepared and investigated a set of peri-substituted naphthalenes containing the protonated dimethylamino group next to the amide nitrogen atom (“amide proton sponges”), which could serve as models for the study of an intramolecular hydrogen bond with the amide nitrogen atom. X-Ray analysis, NMR spectra, basicity values as well as quantum chemical calculations revealed the existence of a hydrogen bond with the amide nitrogen, that should be attributed to the borderline between moderate and weak intramolecular hydrogen bonds (2–7 kcal ⋅ mol−1). 相似文献
7.
IntroductionInrecentyears ,thestudyontheeffectofindoorlight concentrationgaseouspollutiontohumanhealthisdeeplyconcerned .Themainreasonisthat,withtheper fectingoftheindoorgastightnessandheat shieldingper formance ,theappearanceofnewarchitecturalanddeco rati… 相似文献
8.
Two modes of reactivity of N-silylphosphoranimines have been utilized to prepare the title compounds containing either B–N=P or Si–N=P–N–B linkages. First, silicon-nitrogen bond cleavage reactions of the N-silylphosphoranimines, Me3SiN=PMe(R)OCH2CF3 (1: R=Me, 2: R=Ph), with various chloroboranes gave the new N-borylphosphoranimines, Ph(Me2N)B–N=PMe2OCH2CF3 (2) and [(Me3Si)2N](Cl)B–N=PMe2OCH2CF3 (10). In other cases, however, the expected B–N=P products were unstable and cyclic phosphazenes [Me(R)P=N]3,4 were obtained. Second, deprotonation-substitution reactions of the aminophosphoranimines, Me3SiN=P(R)Me–N(R)H, were used to prepare a series of novel (borylamino)-phosphoranimines, Me3SiN=P(R)(Me)–N(R)–B(NMe2)2 (18: R=Me, R=t-Bu; 19: R=R=Me; 20: R=Ph, R=t-Bu; 21: R=Ph, R=Me) and Me3SiN=PMe2–N(t-Bu)–B(Ph)X (22: X=NMe2, 23: X=OCH2CF3). All of the new boron–nitrogen–phosphorus products were fully characterized by multinuclear NMR (1H, 13C, and 31P) spectroscopy and elemental analysis. 相似文献
9.
Junzhi Li Junming Cao Xifei Li Junhua Hu Yaohui Zhang Hirbod Maleki Kheimeh Sari Chunxiao Lv IgorVZatovsky Wei Han 《Journal of Energy Chemistry》2021,(4):420-427
The carbon materials as anode electrodes have been widely studied for potassium ion batteries(PIBs).However,the large size of potassium ions prevents their intercalation/deintercalation,resulting in poor storage behaviors.Herein,a novel design of N/S codoped hierarchical carbonaceous fibers(NSHCF)formed from nanosheets self-assembled by catalyzing Aspergillus niger with Sn is reported.The asprepared NSHCF at 600℃(NSHCF-600)exhibits a high reversible capacity of 345.4 m Ah g-1 at 0.1 A g-1 after 100 cycles and an excellent rate performance of 124.5 m Ah g-1 at 2 A g-1.The excellent potassium storage performance can be ascribed to the N/S dual-doping,which enlarges interlayer spacing(0.404 nm)and introduces more defects.The larger interlayer spacing and higher pyridinic N active sites can promote K ions diffusion and storage.In addition,the ex situ transmission electron microscopy reveals the high reversibility of potassiation/depotassiation process and structural stability. 相似文献
10.
11.
A. D. Antuf’eva M. V. Dmitriev O. A. Maiorova I. G. Mokrushin A. R. Galeev E. V. Shklyaeva G. G. Abashev 《Russian Journal of Organic Chemistry》2018,54(9):1350-1357
A series of ferrocenyl-substituted methyl ketones and chalcones were synthesized and converted to unsymmetrical 4,6-disubstituted pyrimidin-2-amines and 2-(1H-pyrrol-1-yl)pyrimidines in which the ferrocene fragment is separated from the pyrimidine ring by π-deficient (pyridine) or π-excessive (thiophene) heterocycle. The forbidden band gap of the obtained compounds was determined on the basis of their UV spectra (\(E_{\text{g}}^{\text{opt}}\) = 1.75?2.36 eV), and their electrochemical properties were studied. The presence of a thiophene ring between the ferrocene and pyrimidine fragments reduces the redox potential of the ferrocene fragment (20?30 mV), whereas pyridine spacer between the ferrocene and pyrimidine fragment increases the redox potential of the ferrocene fragment by more than 100 mV. 相似文献
12.
Reactivity of dimethyl carbonate, the environmentally friendly reagent, as methylating agent for nitrogen‐containing heterocyclic compounds has been studied. Reactions of imidazole, pyrazole, pyrrole, morpholine, and piperazine with dimethyl carbonate to afford N‐methylated products were reported. The reactions were carried out with neither catalyst nor solvent at a temperature range of 110–170°C under atmospheric pressure. 相似文献
13.
14.
《Journal of carbohydrate chemistry》2013,32(6):433-442
Eight nitrogen heterocycles, mono and disubstituted tetrazoles and oxadiazoles, were synthesized from methyl d‐glucopyranoside anomers. The monosubstituted tetrazoles resulted from the reaction of 6‐cyanoglucopyranoside derivatives with sodium azide. By alkylation of the monosubstituted tetrazoles, the 1,5 and 2,5 disubstituted tetrazoles were obtained. The monosubstituted tetrazoles were reacted with acetic anhydride to give the oxadiazoles. 相似文献
15.
Kenjiro Fujimoto Jun Suzuki Toshiyuki Mori Mamoru Watanabe 《Journal of Sol-Gel Science and Technology》2000,19(1-3):377-381
Fine powder of K
x
Ga
x
Sn8–x
O16 hollandite was prepared by the sol-gel process using metal alkoxides, and the adsorption behavior of nitrogen monoxide (NO) on it was examined by temperature programmed desorption (TPD) method and in situ diffuse reflectance fourier transform infrared spectroscopy. Any species other than nitrogen monoxide were not detected in the TPD measurement, and the profile showed three stages between 420 and 880 K which were regarded as the desorption of chemically adsorbed NO
x
species. This desorption behavior seems well consistent with the spectral changes in the FT-IR measurement. The absorption band at 1270 cm–1 was decayed in the first stage from 420 to 640 K, and the bands at 1235 and 1570 cm–1 in the second stage from 640 and 770 K. In the third stage above 770 K, the strong band at 1340 cm–1 disappeared. These NO
x
species on the hollandite were estimated to have a form of NO3
– in the first and second stages and a form of NO2
– in the third stage, considering the data on adsorption of nitrogen oxides on La2O3 and CaO. 相似文献
16.
A short and convenient synthesis of two series of eight totally new lariat crown ethers is reported in this article. These lariat ethers are derived from triaza‐dibenzo‐27‐crown‐7 and diaza‐dibenzo‐27‐crown‐7 through condensation of appropriate aza‐crown ethers with appropriate substituted compounds in chloroform. The substituted reagents are acetic anhydride, benzoyl chloride, phthalic anhydride, and butanedioic anhydride, respectively. 相似文献
17.
18.
Lobo L Fernandez B Pereiro R Bordel N Sanz-Medel A 《Analytical and bioanalytical chemistry》2007,389(3):743-752
A study about the effect of nitrogen in the calibration curves of a series of analytical emission lines has been carried out
in this work. Fifteen reference materials with different matrices (Fe, Al, Zn, Cu and Ni) were used (three of these reference
materials contain nitrogen in their composition) and plots of intensity versus the product “sputtering rate times element
concentration” were constructed for emission lines of the analytes considered in this work (Al, Fe, Cu, Cr, C, Mo, Zn, Si,
Ti and Ni). Two different fits were performed in each plot, first considering only the points corresponding to samples without
nitrogen in their composition and secondly including all the points. The results show almost negligible differences in the
emission yields calculated. On the other hand, a mixture of Ar containing 0.5% N2 was employed to check if the nitrogen effect was present at higher concentrations than those expected in analysis when samples
with high nitrogen concentrations are used. Differences between the slopes of the calibration curves with the Ar/N2 and pure Ar discharges were obtained (up to 30%). A study of the molecular bands recorded in the spectra when nitrogen is
present in the discharge and determination of the resulting interferences on the analytes have been performed.
Figure Glow discharge powered with radiofrequency energy 相似文献
19.
Idan Avigdori Dr. Alla Pogoreltsev Dr. Alexander Kaushanski Dr. Natalia Fridman Prof. Dr. Mark Gandelman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23682-23685
N-heterocyclic nitrogen Lewis acids are a recent addition to the field of organic chemistry. Based on nitrenium cations, these acids where previously shown to generate Lewis adducts when combined with the appropriate Lewis bases. Herein, a triazinium-based Lewis acid was combined with tBu3P to generate a frustrated Lewis pair (FLP) capable of cleaving, for the first time, Si−H bonds in silanes. Whereas low yields were initially encountered owing to insufficient Lewis acidity, a new nitrenium-based Lewis acid was synthesized, and its superior Lewis acidity was experimentally and computationally confirmed. A FLP based on this acid cleaved the Si−H bond in PhSiH3, generating the triazane product in a quantitative yield. This unprecedented N−H triazane was fully characterized by multinuclear NMR techniques and single-crystal X-ray crystallography. A new class of compounds, N-H triazanes display the potential capacity to participate in hydride transfer reactions. 相似文献
20.
Today it is possible to replace the costly Kjeldahl method by the commonly used Carrier Gas Hot Extraction (CGHE) method for the determination of nitrogen contents of up to 50wt%, because the accuracy of this method was improved up to a 0.2% relative standard deviation. The remaining problem is the availability of defined and stable standards for N analyses by Carrier Gas Hot Extraction. In this study, we compared different certified standards with -TaN, which is a so-called line compound with a defined nitrogen content.A nitrogen content of almost theoretical composition was found for -TaN using compact samples analysed by CGHE and combustion-GC (Dumas-GC) analysis while the nitrogen content decreased in powdered samples. -TaN is a well-suited and stable potential reference material especially if the gas analyser is capable of analysing and decomposing compact pieces of this material. 相似文献