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281.
282.
A mild and efficient protocol for the synthesis of spiro[indoline-3,4′-pyrazolo[3,4-b]quinoline]diones via a one-pot, three-component condensation of isatins, 1,3-dicarbonyls, and 5-amino-1-phenyl-3-methylpyrazole using [NMP]H2PO4 as a catalyst in EtOH/H2O is described. The catalyst could be recycled and reused four times without significant loss of activity. Spiro[indoline-3,4′-pyrazolo[3,4-b]quinoline]diones with stabilized zwitter ionic resonance structures showed feasible application as new fluorescent probes and pH indicators. These chemosensors have a good wavelength shift and showed excellent sensitivity in the range of pH from 11 to 13. 相似文献
283.
284.
Jai Devi Suman Kumari Sonika Asijaa Rajesh Malhotra 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):1409-1417
Abstract Hexacoordinated organosilicon complexes of type R3Si(L) (R = ethyl, butyl, phenyl; HL = ligand, obtained by the condensation of 4-aminoantipyrine with 2-hydroxyacetophenone, 2-hydroxybenzophenone, 2-hydroxybenzaldehyde, and 2-hydroxynapthaldehyde) have been synthesized and characterized by elemental analysis, molar conductance, and spectroscopic studies (IR, 1H, 13C, and 29Si NMR). The spectroscopic studies indicated that the ligands acted as tridentate coordinating through azomethine nitrogen, carbonyl oxygen, and oxygen of hydroxyl after deprotonation to the central silicon atom. The ligands and their organosilicon complexes have been evaluated for antimicrobial activities against fungi (Aspergillus niger and Candida albicans), and against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis), and Gram-negative bacteria (Escherichia coli). The aim of the present work is to synthesize novel eco-friendly fungicides and bactericides and to study the effect of the biological activity of ligands on the complexation with organosilicon moiety. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
285.
Dudekula Sharmila K. Yuvaraj Subrat Kumar Barik Dipak Kumar Roy Kiran Kumarvarma Chakrahari Rongala Ramalakshmi Bijan Mondal Dr. Babu Varghese Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15219-15225
The synthesis, structural characterization, and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}2] with LiBH4 ? THF at ?70 °C, followed by treatment with [M(CO)3(MeCN)3] (M=W, Mo, and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(μ3‐BH)(Cp*Co)2(μ‐CO)M(CO)5] ( 1 – 3 ; 1 : M=W, 2 : M=Mo, 3 : M=Cr). During the syntheses of complexes 1 – 3 , capped‐octahedral cluster [(Cp*Co)2(μ‐H)(BH)4{Co(CO)2}] ( 4 ) was also isolated in good yield. Complexes 1 – 3 are isoelectronic and isostructural to [(μ3‐BH)(Cp*RuCO)2(μ‐CO){Fe(CO)3}] ( 5 ) and [(μ3‐BH)(Cp*RuCO)2(μ‐H)(μ‐CO){Mn(CO)3}] ( 6 ), with a trigonal‐pyramidal geometry in which the μ3‐BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis‐phosphine ligands, the room‐temperature photolysis of complexes 1 – 3 , 5 , 6 , and [{(μ3‐BH)(Cp*Ru)Fe(CO)3}2(μ‐CO)] ( 7 ) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph2P(CH2)nPPh2] (n=1–3) yielded complexes 9 – 11 , [3,4‐(Ph2P(CH2)nPPh2)‐closo‐1,2,3,4‐Ru2Fe2(BH)2] ( 9 : n=1, 10 : n=2, 11 : n=3). Quantum‐chemical calculations by using DFT methods were carried out on compounds 1 – 3 and 9 – 11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO–LUMO gaps, in accordance with the high stabilities of these complexes, and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy, and 1H, 13C, and 11B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1 , 2 , 4 , 9 , and 10 . 相似文献
286.
Subash C. Verma Chhoten L. Jain Amita Kumari Madan M. Padhi Ramesh B. Devalla 《Journal of separation science》2013,36(7):1255-1262
Ursolic acid (UA) is the most important bioactive phytoconstituent of Eucalyptus × hybrida Maiden leaves and exhibits anticancer, antimutagenic, anti‐inflammatory, antioxidative, and antiprotozoal activities. In this study, microwave‐assisted extraction technique was employed for rapid isolation of UA from the leaves of Eucalyptus × hybrida and simultaneously HPLC‐diode array method was developed for the quantification of UA. Effects of several experimental parameters on the extraction efficiencies of UA, such as type and volume of extraction solvents, microwave power and extraction time, were evaluated. The optimal extraction conditions were found to be 20 mL of a mixture of chloroform/methanol, 60:40; liquid‐to‐material ratio, 4:1; preleaching time, 10 min; microwave power, 600 W; temperature, 50°C; and microwave irradiation time, 5 min. Under the optimum conditions, the yield of UA was found to be 1.95 ± 0.08% in the dry leaves of Eucalyptus × hybrida. The results showed that microwave‐assisted extraction is a more rapid extraction method with higher yield and lower solvent consumptions than the conventional method. It is a faster, convenient, and appropriate method and it may be used for rapid isolation and quantification of UA and other important phytoconstituents present in the leaves of Eucalyptus × hybrida. 相似文献
287.
Dr. Amit Kumar Dr. Nitee Kumari Dr. Sateesh Dubbu Dr. Sumit Kumar Taewan Kwon Dr. Jung Hun Koo Jongwon Lim Inki Kim Prof. Yoon-Kyoung Cho Prof. Junsuk Rho Prof. In Su Lee 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9547-9556
Interest and challenges remain in designing and synthesizing catalysts with nature-like complexity at few-nm scale to harness unprecedented functionalities by using sustainable solar light. We introduce “nanocatalosomes”—a bio-inspired bilayer-vesicular design of nanoreactor with metallic bilayer shell-in-shell structure, having numerous controllable confined cavities within few-nm interlayer space, customizable with different noble metals. The intershell-confined plasmonically coupled hot-nanospaces within the few-nm cavities play a pivotal role in harnessing catalytic effects for various organic transformations, as demonstrated by “acceptorless dehydrogenation”, “Suzuki–Miyaura cross-coupling” and “alkynyl annulation” affording clean conversions and turnover frequencies (TOFs) at least one order of magnitude higher than state-of-the-art Au-nanorod-based plasmonic catalysts. This work paves the way towards next-generation nanoreactors for chemical transformations with solar energy. 相似文献
288.
289.
The paper deals with the exploitation of Ipomoea carnea as a feedstock for the production of bioethanol. Dilute acid pretreatment under optimum conditions (3 %H2SO4, 120 °C for 45 min) produced 17.68 g L?1 sugars along with 1.02 g L?1 phenolics and 1.13 g L?1 furans. A combination of overliming and activated charcoal adsorption facilitated the removal of 91.9 % furans and 94.7 % phenolics from acid hydrolysate. The pretreated biomass was further treated with a mixture of sodium sulphite and sodium chlorite and, a maximum lignin removal of 81.6 % was achieved. The enzymatic saccharification of delignified biomass resulted in 79.4 % saccharification with a corresponding sugar yield of 753.21 mg g?1. Equal volume of enzymatic hydrolysate and acid hydrolysate were mixed and used for fermentation with a hybrid yeast strain RPRT90. Fermentation of mixed detoxified hydrolysate at 30 °C for 28 h produced ethanol with a yield of 0.461 g g?1. A comparable ethanol yield (0.414 g g?1) was achieved using a mixture of enzymatic hydrolysate and undetoxified acid hydrolysate. Thus, I. carnea biomass has been demonstrated to be a potential feedstock for bioethanol production, and the use of hybrid yeast may pave the way to produce bioethanol from this biomass. 相似文献
290.
ABSTRACT Mutans streptococcus glucosyltransferases are the significant virulent factors in causing dental caries. The binding specificity of acarbose was probed with glucosyl and fructosyl sub-site binding ligands using multiple inhibition kinetics. The results indicate that acarbose and a glucosyl subsite binding ligand (1-deoxynojirimycin) are mutually or partially exclusive. On the other hand, acarbose with a fructosyl subsite ligand (fructose) might induce a conformational change leading to enhanced binding at the adjacent subsite. 相似文献