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981.
Redox‐Neutral α‐Allylation of Amines by Combining Palladium Catalysis and Visible‐Light Photoredox Catalysis
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Jun Xuan Ting‐Ting Zeng Zhu‐Jia Feng Qiao‐Hui Deng Prof. Dr. Jia‐Rong Chen Dr. Liang‐Qiu Lu Prof. Dr. Wen‐Jing Xiao Prof. Dr. Howard Alper 《Angewandte Chemie (International ed. in English)》2015,54(5):1625-1628
An unprecedented α‐allylation of amines was achieved by combining palladium catalysis and visible‐light photoredox catalysis. In this dual catalysis process, the catalytic generation of allyl radical from the corresponding π‐allylpalladium intermediate was achieved without additional metal reducing reagents (redox‐neutral). Various allylation products of amines were obtained in high yields through radical cross‐coupling under mild reaction conditions. Moreover, the transformation was applied to the formal synthesis of 8‐oxoprotoberberine derivatives which show potential anticancer properties. 相似文献
982.
Le Guo Xiaochen Ma Huaquan Fang Xiangqing Jia Prof. Dr. Zheng Huang 《Angewandte Chemie (International ed. in English)》2015,54(13):4023-4027
Catalytic α‐alkylation of esters with primary alcohols is a desirable process because it uses low‐toxicity agents and generates water as the by‐product. Reported herein is a NCP pincer/Ir catalyst which is highly efficient for α‐alkylation of a broad scope of unactivated esters under mild reaction conditions. For the first time, alcohols alkylate unactivated α‐substituted acyclic esters, lactones, and even methyl and ethyl acetates. This method can be applied to the synthesis of carboxylic acid derivatives with diverse structures and functional groups, some of which would be impossible to access by conventional enolate alkylations with alkyl halides. 相似文献
983.
Teng‐Shuo Zhang Rui Du Yan‐Yin Zhao Jia‐Dan Xue Hui‐Gang Wang Xuming Zheng 《Journal of Raman spectroscopy : JRS》2016,47(3):299-309
The B‐band resonance Raman spectra of 2(1H)‐pyridinone (NHP) in water and acetonitrile were obtained, and their intensity patterns were found to be significantly different. To explore the underlying excited state tautomeric reaction mechanisms of NHP in water and acetonitrile, the vibrational analysis was carried out for NHP, 2(1D)‐pyridinone (NDP), NHP–(H2O)n (n = 1, 2) clusters, and NDP–(D2O)n (n = 1, 2) clusters on the basis of the FT‐Raman experiments, the B3LYP/6‐311++G(d,p) computations using PCM solvent model, and the normal mode analysis. Good agreements between experimental and theoretically predicted frequencies and intensities in different surrounding environments enabled reliable assignments of Raman bands in both the FT‐Raman and the resonance Raman spectra. The results indicated that most of the B‐band resonance Raman spectra in H2O was assignable to the fundamental, overtones, and combination bands of about ten vibration modes of ring‐type NHP–(H2O)2 cluster, while most of the B‐band resonance Raman spectra in CH3CN was assigned to the fundamental, overtones, and combination bands of about eight vibration modes of linear‐type NHP–CH3CN. The solvent effect of the excited state enol‐keto tautomeric reaction mechanisms was explored on the basis of the significant difference in the short‐time structural dynamics of NHP in H2O and CH3CN. The inter‐molecular and intra‐molecular ESPT reaction mechanisms were proposed respectively to explain the Franck–Condon region structural dynamics of NHP in H2O and CH3CN.Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
984.
Wei-Wei Jiang Jia Su Xing-De Wu Juan He Li-Yan Peng Xiao Cheng 《Natural product research》2015,29(9):842-847
Geissoschizine methyl ether N-oxide, a new oxindole alkaloid, along with 14 known alkaloids, was isolated from the aerial part of Uncaria rhynchophylla. Their structures were identified by comprehensive spectral methods, including 2D NMR experiments, and confirmed by comparing with the literature data. In vitro acetylcholinesterase (AChE) inhibitory activity assay showed that the new compound exhibited anti-AChE activity with IC50 value of 23.4 μM. 相似文献
985.
Preparation of a monolith functionalized with zinc oxide nanoparticles and its application in the enrichment of fluoroquinolone antibiotics
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Dan Liu Jiutong Ma Yan Jin Xiqian Li Xiao Zhou Qiong Jia Weihong Zhou 《Journal of separation science》2015,38(1):134-140
This study describes the enrichment ability of ZnO‐modified methacrylic acid‐co‐ethylene dimethacrylate polymer monoliths as stationary phases for the simultaneous determination of antibiotics (ofloxacin, ciprofloxacin, enoxacin, and pefloxacin) combined with high‐performance liquid chromatography. The prepared monolith was characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier‐transformed infrared spectroscopy, and thermogravimetric analysis. The polymer monolith microextraction method has been applied to the enrichment of fluoroquinolone antibiotics and satisfactory results were obtained in the analysis of water samples. Compared with the conventional methacrylic acid based monolith, the developed monolith exhibited a higher enrichment capacity because of the introduction of zinc oxide into the preparation process. 相似文献
986.
Separation and purification of five alkaloids from Aconitum duclouxii by counter‐current chromatography
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Yarong Wang Shining Cai Yang Chen Xumei Zhou Jia Liu Xin Xu Qiang Xia Mao Lin Jili Zhang Weili Huang Wenjun Wang Canhui Xiang Guozhen Cui Lianfeng Du Huan He Baohui Qi 《Journal of separation science》2015,38(13):2320-2326
C19‐diterpenoid alkaloids are the main components of Aconitum duclouxii Levl. The process of separation and purification of these compounds in previous studies was tedious and time consuming, requiring multiple chromatographic steps, thus resulted in low recovery and high cost. In the present work, five C19‐diterpenoid alkaloids, namely, benzoylaconine ( 1 ), N‐deethylaconitine ( 2 ), aconitine ( 3 ), deoxyaconitine ( 4 ), and ducloudine A ( 5 ), were efficiently prepared from A. duclouxii Levl (Aconitum L.) by ethyl acetate extraction followed with counter‐current chromatography. In the process of separation, the critical conditions of counter‐current chromatography were optimized. The two‐phase solvent system composed of n‐hexane/ethyl acetate/methanol/water/NH3·H2O (25%) (1:1:1:1:0.1, v/v) was selected and 148.2 mg of 1 , 24.1 mg of 2 , 250.6 mg of 3 , 73.9 mg of 4, and 31.4 mg of 5 were obtained from 1 g total Aconitum alkaloids extract, respectively, in a single run within 4 h. Their purities were found to be 98.4, 97.2, 98.2, 96.8, and 96.6%, respectively, by ultra‐high performance liquid chromatography analysis. The presented separation and purification method was simple, fast, and efficient, and the obtained highly pure alkaloids are suitable for biochemical and toxicological investigation. 相似文献
987.
The Convenient Synthesis of 11‐Methyl‐3,8‐disubstituted‐12‐aryl‐3,4,7,8,9,12‐hexahydro‐1H‐chromeno[2,3‐b]quinoline‐1,10(2H)‐dione Derivatives
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Guang‐Fan Han Li‐Jun Zhao Li‐Zhuang Chen Jia‐Wei Du Zhong‐Xia Wang 《Journal of heterocyclic chemistry》2015,52(4):1219-1225
The 2‐arylidene‐3‐oxobutanenitrile derivatives 2 were prepared by the Knoevenagel condensation between aldehydes and 3‐oxobutanenitrile 1 , which was obtained by acid hydrolysis of β‐aminocrotononitrile. 3‐Acetyl‐2‐amino‐4H‐chromen‐5(6H)‐one derivatives 3 were synthesized by reaction of 2‐arylidene‐3‐oxobutanenitrile 2 and 5‐substituted‐1,3‐cyclohexanedione in ethylene glycol. The 11‐methyl‐3,8‐disubstituted‐12‐aryl‐3,4,7,8,9,12‐hexahydro‐1H‐chromeno[2,3‐b]quinoline‐1,10(2H)‐dione derivatives 4 were obtained by Friedländer reaction of compounds 3 with 5‐substituted‐1,3‐cyclohexanedione, using p‐toluenesulfonic acid monohydrate as catalyst. The structures of all novel compounds were characterized by elemental analysis, IR, MS, and 1H NMR spectra. The crystal and molecular structure of compound 4f has been determined by single crystal XRD analysis. 相似文献
988.
以巯基乙酸甲酯(MT)修饰的纳米金(AuNPs)为探针,构建了比色生物传感器检测脂肪酶活性.在pH 6.5弱酸性条件下,脂肪酶水解MT-AuNPs上的酯键生成带负电荷的羧酸根;在pH 3.0的酸性条件下,探针间会产生强烈的氢键作用使AuNPs聚集,基于此可以检测脂肪酶活性.考察了温度、pH等因素对传感器响应信号的影响.MT-AuNPs溶液在650和520 nm处的吸光度比值A650/A520与脂肪酶活性大小在3.0×10-4 ~4.5 ×10-2 U/mL范围内呈现良好的线性关系,检出限为2.25×10-4 U/mL(S/N=3).测定了5种商品化脂肪酶的活性,实验结果与恒电位滴定法测定结果一致,证明本方法具有良好的实用性. 相似文献
989.
990.
Thermal Cyclization of Copper Carbenoid of α‐Dizao α‐Phosphorylacetate: Unexpected and Novel Access to Oxaphosphirane
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Under the catalysis of Cu(OTf)2 in refluxing CH2Cl2, ethyl α‐dizao α‐(diethylphosphoryl)acetate was shown to undergo a new cyclization reaction to afford a pentacovalent oxaphosphirane product. The reaction is proposed to occur through the addition of the P=O double bond to the copper carbenoid, followed by the hydrolysis of the ylide intermediate. Our finding represents the first example on producing oxaphosphiranes from dizao phosphoryl compounds. On the other hand, the corresponding rhodium carbenoid displayed the different reactivity under the same thermal conditions, to produce the β‐propiolactone through the well‐recognized C‐H insertion pathway. 相似文献