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31.
Wei Qin Rishabh Jain Francisco C. Robles Hernández Prof. Dr. Jeffrey D. Rimer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5893-5898
Zeolite crystals can be used as seeds or aluminosilicate sources in syntheses to control polymorphs and/or reduce the quantity of organics used as structure-directing agents. A frequently invoked hypothesis for interzeolite transformations is that zeolites share some underlying similarity in structure, most notably in cases pertaining to organic-free syntheses. Herein, we show for the first time that ZSM-5 (MFI) can be directly obtained from USY (FAU) through an interzeolite transformation between parent–daughter structures lacking common building units in the absence of a structure-directing agent and seeds. We show that interzeolite transformation leads to a crystalline product with fewer defects. Our findings also reveal that ZSM-5 is a metastable intermediate that undergoes further transformation to mordenite (MOR) and quartz. The MFI-to-MOR transition is counter to reported trends for which transformations lead to structures with reduced molar volume. Herein, we propose mechanistic arguments that suggest the driving force for interzeolite transformation is more complex than guidelines posited in the literature. 相似文献
32.
The one-pot, three-step, four-component Ugi-IMDAF reaction with 5-hydroxymethylfurfural provides simple access to hydroxymethyl-substituted epoxyisoindolones in a diastereoselective and stereospecific manner. The protocol avoids the transfer or isolation of isocyanides, and the broad scope was illustrated by the synthesis of 22 different compounds bearing various substituents on the heterocyclic core. 相似文献
33.
Easy and effective preparation of new 1H-pyrrolizine carboxylates was achieved with high efficiency via KHMDS-induced carbocyclization of N-alkynyl proline carboxylates under substantially mild conditions. Meanwhile, some trans-diiodoallylic N-proline carboxylates were obtained from N-propargyl proline carboxylates using molecular I2 with or without KHMDS. This method is quite feasible in terms of practical and quick access to the pyrrolizines and their derivatives over the formation of carbanions. 相似文献
34.
O. V. Golovchenko E. R. Abdurakhmanova S. O. Vladimirov M. Y. Brusnakov T. O. Krupoder V. V. Sukhoveev 《Phosphorus, sulfur, and silicon and the related elements》2020,195(10):848-857
AbstractIt is shown that the interaction of 1-acylamino-2,2-dichloroethenyl(triphenyl)-phosphonium chlorides with alkanolamines having a primary amino group results in the formation of 4-oxazolylphosphonium salts containing hydroxyalkylamine substituents at position 5 of the oxazole cycle. Under similar conditions the reaction of N-substituted alkanolamines with 1-acylamino-2,2-dichloroethenyl-(triphenyl)phosphonium chlorides leads to the formation of 1,3-oxazolidin-2-ylidene derivatives, in which the triphenylphosphonium group is located in the side chain. The structure of the new synthesized compounds has been reliably proven by elemental analysis, IR, 1Н, 13С, 31Р NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction. 相似文献
35.
Fanghua Zhang Jiwei Yin Chao Zhang Mengnan Han Xuming Wang Shuangqing Fu Jie Du Honglei Zhang Wei Li 《Macromolecular bioscience》2020,20(7)
Affibody‐conjugated RALA (affi‐RA) are designed for delivering oligomeric 5‐fluorodeoxyuridine (FUdR, metabolite of 5‐FU) strand to raise the selectivity of 5‐fluorouracil (5‐FU), decrease its toxicity and improve its suboptimal therapeutic efficacy. The nanodrugs, FUdR@affi‐RA, are spontaneously assembled by electrostatic interaction between positively charged affi‐RA and negatively charged FUdR15‐strands (15 consecutive FUdR). FUdR@affi‐RA exhibits excellent stability under simulated physiological conditions. Compared with free FUdR, FUdR@affi‐RA shows excellent targeting and higher cytotoxicity in human epidermal growth factor receptor 2 (HER2) overexpressing gastric cancer N87 cells. Moreover, the anticancer mechanism studies reveal that FUdR@affi‐RA enhances the expression and activity of apoptosis‐associated proteins in the Bcl‐2/Bax‐caspase 8,9‐caspase 3 apoptotic pathway induced by FUdR. This study indicates that the fusion vector, affi‐RA, presents a promising delivery system platform for nucleoside analogue drugs and provides a new strategy for the development of therapeutics of cancer treatment. 相似文献
36.
The electronic sensitivity and effectiveness of the pristine, Fe,- Mg-, Al- and Ga-doped ZnO nanoclusters interacted with 5-fluorouracil (5-FU) anticancer drug are theoretically investigated in the gas phase using the B3LYP/wB97XD density functional theory calculations with LANL2DZ basis set. It is concluded that 5-FU adsorption on the doped nanoclusters has relatively higher adsorption energy as compared with the pristine zinc oxide. A number of thermodynamic parameters, such as band gap energy (Eg), adsorption energy (Ead), molecular electrostatic potential, global hardness (η) and density of electronic states, are attained and compared. Also, calculated geometrical parameters and electronic properties for the studied systems indicate that Mg- and Ga-doped Zn12O12 present higher sensitivity to 5-FU compared with the pristine nanocluster. Theoretical results reveal that adsorption of 5-FU on the doped nanoclusters is influenced by the electronic conductance of the nanocluster. Therefore, Mg- and Ga-doped ZnO can be considered as promising nanobiosensors for detection of 5-FU in medicine. 相似文献
37.
Jun-Rui Lyu Shao-Yi Wu Yu-Jing Hong Hao Wu Hui-Ning Dong 《Magnetic resonance in chemistry : MRC》2022,60(3):398-406
In this work, the g factors, d–d transition band, local distortion, and their concentration dependences for impurity V4+ in 20Li2O–20PbO–45B2O3–(15 − x)P2O5:V2O5 (0 ≤ x ≤ 2.5 mol%) glasses are theoretically investigated by using perturbation formulas of g factors for a tetragonally compressed octahedral 3d1 cluster. In the light of the cubic polynomial concentration functions for cubic field parameter Dq, covalency factor N, and relative tetragonal compression ratio ρ, the calculated concentration dependences of d–d transition band and g factors for V4+ show good agreement with the experimental data. With increasing x, N (≈0.7682–0.8165) displays the monotonously increasing trend, whereas ρ (≈6.5–4.2%) and Dq (≈1504.9–1481.1 cm−1) exhibit the decreasing tendencies. The above concentration dependences can be ascribed to the modifications of the V4+–O2− bonding and orbital admixtures around the impurity V4+ due to the effects of V2O5 doping on the stability of the glass network, the strength of local crystal fields, and the electron cloud distribution. 相似文献
38.
Synthesis of 5‐substituted 1H‐tetrazoles using a recyclable heterogeneous nanonickel ferrite catalyst 下载免费PDF全文
An efficient method was developed for the [2 + 3] cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles using nanonickel ferrite (NiFe2O4) as an effective heterogeneous catalyst in dimethylformamide. The main advantages of this method are high yields, simple methodology and easy work‐up. The catalyst can be recovered and reused for several cycles with predictable activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
39.
40.
Unraveling the Degradation Mechanism of Purine Nucleotides Photosensitized by Pterins: The Role of Charge‐Transfer Steps 下载免费PDF全文
Mariana P. Serrano Dr. Carolina Lorente Dr. Claudio D. Borsarelli Dr. Andrés H. Thomas 《Chemphyschem》2015,16(10):2244-2252
Photosensitized reactions contribute to the development of skin cancer and are used in many applications. Photosensitizers can act through different mechanisms. It is currently accepted that if the photosensitizer generates singlet molecular oxygen (1O2) upon irradiation, the target molecule can undergo oxidation by this reactive oxygen species and the reaction needs dissolved O2 to proceed, therefore the reaction is classified as 1O2‐mediated oxidation (type II mechanism). However, this assumption is not always correct, and as an example, a study on the degradation of 2′‐deoxyguanosine 5′‐monophosphate photosensitized by pterin is presented. A general mechanism is proposed to explain how the degradation of biological targets, such as nucleotides, photosensitized by pterins, naturally occurring 1O2 photosensitizers, takes place through an electron‐transfer‐initiated process (type I mechanism), whereas the contribution of the 1O2‐mediated oxidation is almost negligible. 相似文献