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51.
Platinum‐Catalyzed Cascade Rearrangement Reaction of 1,5‐Diynyl Esters: Unusual Regioselective 1,5‐Hydride Migration 下载免费PDF全文
A highly regioselective sequential 1,3‐acyloxy migration/pentannulation/1,5‐hydride migration reaction is disclosed which provides an efficient access to (E)‐2‐vinyl‐3‐oxo‐1‐methyleneindenes under neutral and mild reaction conditions. The migrated hydrogen atom was derived from an unactivated alkyl group, and the long‐range 1,5‐H shift was confirmed through related deuterium experiments. 相似文献
52.
A microwave-assisted general method for the synthesis of 2-aminovinyl benzimidazoles has been developed.Treatment of the 1,2-phenylenediamines and N-arylated/N,N-dialkylated 3-aminoacroleins with bis(cyclopentadienyl)zirconium(IV) dichloride(Cp2Zr Cl2) as the catalyst under microwave irradiation for 3–5 min followed by in situ Mn O2 oxidation afforded thirteen 2-aminovinyl benzimidazoles in good yields. 相似文献
53.
Hui Zhao Xiang-Guo Hu Min-Jie Xu Qun-Xing Cai Yu-Jun Liu Duo-Meng Su Shi-Jin Chen Kai Wang Zhu-Nan Gong 《中国化学快报》2017,28(6):1172-1175
Leonurine (1), an important ingredient in leonurus sibiricus L., can be used for some gynecological disease. We have developed a concise and efficient synthetic route of Leonurine, which can be optimized for mass production. Commercially available compound 6 and 2,3-dihydrofuran (7) were used as starting materials. And the toxicity study on zebrafish shows that Leonurine would promote the hatching of zebrafish embryos at low concentration and result in acute death or chronic lethal toxicity at high concentration. 相似文献
54.
Xiaoyu Li Cuiqing Zhang Changyuan Hu Linchong Xu Quanhong Hu Shuwang Duo Wenkui Li Yongfang Kang 《Journal of Cluster Science》2017,28(5):2409-2418
A novel Bi2O4@TiO2 heterojunction was constructed by a simple two-step method. The charges migration between Bi2O4 and TiO2 via the heterojunction improves the electron/hole separation efficiency. Furthermore, Bi2O4@TiO2 heterostructures exhibit better adsorption capability for methyl orange molecular due to their higher specific surface area than pure Bi2O4. As a result, Bi2O4@TiO2 hybrids show an improved visible light photocatalytic activity and photostability for the degradation of methyl orange. 相似文献
55.
56.
Molecular self-assembly offers a promising route to the preparation of advanced materials for the construction of novel chiral sensing devices, and the inspiration for the development of such systems is often derived from simple biological models. Diphenylalanine (FF), an extensively studied short peptide, can self-assemble into highly ordered nano-/micro-structures. Here we report the electrochemical recognition of tryptophan enantiomers using three FF self-assembled structures produced in the presence of graphene quantum dots (GQDs), chitosan (CS) and cetyltrimethylammonium bromide (CTAB). Although the difference in the peak potentials of the enantiomers is very small, enantiomeric differences can be detected by the magnitude of the DPV current signals. The recognition efficiencies of the three self-assembled materials are different, due to the different structures formed during the self-assembly process. 相似文献
57.
Guo Ye Jingkun Xu Xiumei Ma Qianjie Zhou Danqin Li Xiaoyu Liang Xuemin Duan Weiqiang Zhou 《Journal of Solid State Electrochemistry》2017,21(1):81-90
In this paper, poly[poly(N-vinyl-carbazole)] (PPVK) films electrodeposited in tetrahydrofuran (THF) containing 12 % boron trifluoride diethyl etherate (BFEE) were studied as electrode active material for supercapacitors. The morphology and thermal property were characterized by SEM, atomic force microscopy (AFM), and thermogravimetry (TG), respectively. The electrochemical capacitive behaviors of the PPVK films were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The electrochemical results showed that the specific capacitance of PPVK films in CH3CN solution was about 126 mF cm?2 at 1.5 mA cm?2 and the capacitance retention was only 14.4 % after 1000 cycles. It was exciting to improve the specific capacitance up to 169.3 mF cm?2 at 1.5 mA cm?2 and to make the cyclic stability increase to 81.8 % capacitance retention after 5000 cycles when the equivalent BFEE was added into the CH3CN solution containing 0.05 M Bu4NBF4 electrolyte. These results clearly demonstrated that BFEE was an efficient promoter for the enhancement of the capacitance performance of PPVK films. Therefore, with the help of BFEE electrolyte, the PPVK films have potential application as capacitive materials in high-performance energy storage devices. 相似文献
58.
Recently Haezendonck–Goovaerts (H–G) risk measure has received much attention in (re)insurance and portfolio management. Some nonparametric inferences have been proposed in the literature. When the loss variable does not have enough moments, which depends on the involved Young function, the nonparametric estimator in Ahn and Shyamalkumar (2014) has a nonnormal limit, which challenges interval estimation. Motivated by the fact that many loss variables in insurance and finance could have a heavier tail such as an infinite variance, this paper proposes a new estimator which estimates the tail by extreme value theory and the middle part nonparametrically. It turns out that the proposed new estimator always has a normal limit regardless of the tail heaviness of the loss variable. Hence an interval with asymptotically correct confidence level can be obtained easily either by the normal approximation method via estimating the asymptotic variance or by a bootstrap method. A simulation study and real data analysis confirm the effectiveness of the proposed new inference procedure for estimating the H–G risk measure. 相似文献
59.
In this paper, let α be any real number between 0 and 2, we study the Dirichlet problem for semi-linear elliptic system involving the fractional Laplacian: We will first establish the equivalence between PDE problem (1) and the corresponding integral equation (IE) system (Lemma 2). Then we use the moving planes method in integral forms to establish our main theorem, a Liouville type theorem for the integral system (Theorem 3). Then we conclude the Liouville type theorem for the above differential system involving the fractional Laplacian (Corollary 4).
相似文献
$$\left \{\begin {array}{l} (-{\Delta })^{\alpha /2}u(x)=v^{q}(x),\ \ \ x\in \mathbb {R}^{n}_{+},\\ (-{\Delta })^{\alpha /2}v(x)=u^{p}(x),\ \ \ x\in \mathbb {R}^{n}_{+},\\ u(x)=v(x)=0,\ \ \ \ \ \ \ \ \ \ x\notin \mathbb {R}^{n}_{+}. \end {array}\right .\label {elliptic} $$
(1)