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991.
Long‐Lived Trifluoromethanide Anion: A Key Intermediate in Nucleophilic Trifluoromethylations
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Prof. Dr. G. K. Surya Prakash Dr. Fang Wang Zhe Zhang Prof. Dr. Ralf Haiges Dr. Martin Rahm Prof. Dr. Karl O. Christe Dr. Thomas Mathew Prof. Dr. George A. Olah 《Angewandte Chemie (International ed. in English)》2014,53(43):11575-11578
The trifluoromethanide anion is the postulated key intermediate in nucleophilic trifluoromethylation reactions. However, for more than six decades, the trifluoromethanide anion was widely believed to exist only as a short‐lived transient species in the condensed phase. It has now been prepared in bulk for the first time in THF solution. The trifluoromethanide anion with the [K(18‐crown‐6)]+ cation was unequivocally characterized by low‐temperature 19F and 13C NMR spectroscopy. Its intermediacy in nucleophilic trifluoromethylation reactions was directly evident by its reaction chemistry with various electrophilic substrates. Variable‐temperature NMR spectroscopy, along with quantum mechanical calculations, support the persistence of the trifluoromethanide anion. 相似文献
992.
Analytical formulas for next-to-leading order temperature corrections to the thermal state variables of interacting nucleons in bulk matter are derived in the degenerate limit. The formalism developed is applicable to a wide class of non-relativistic and relativistic models of hot and dense matter currently used in nuclear physics and astrophysics (supernovae, proto-neutron stars and neutron star mergers) as well as in condensed matter physics. We consider the general case of arbitrary dimensionality of momentum space and an arbitrary degree of relativity (for relativistic models). For non-relativistic zero-range interactions, knowledge of the Landau effective mass suffices to compute next-to-leading order effects, but for finite-range interactions, momentum derivatives of the Landau effective mass function up to second order are required. Results from our analytical formulas are compared with the exact results for zero- and finite-range potential and relativistic mean-field theoretical models. In all cases, inclusion of next-to-leading order temperature effects substantially extends the ranges of partial degeneracy for which the analytical treatment remains valid. Effects of many-body correlations that deserve further investigation are highlighted. 相似文献
993.
Ramu Rajasekaran Prakash Rao Aruna Dornadula Koteeswaran Loganathan Padmanabhan Kulandaivel Muthuvelu Ram Rathan Rai Palraj Thamilkumar Chilakapati Murali Krishna Singaravelu Ganesan 《Photochemistry and photobiology》2013,89(2):483-491
Urine is one of the diagnostically important bio fluids, as it has different metabolites in it, where many of them are native fluorophores. Native fluorescence characteristics of human urine samples were studied using excitation–emission matrices (EEMs) over a range of excitation and emission wavelengths, and emission spectra at 405 nm excitation, to discriminate patients with cancer from the normal subjects. The fluorescence spectra of urine samples of cancer patients exhibit considerable spectral differences in both EEMs and emission spectra with respect to normal subjects. Different ratios were calculated using the fluorescence intensity values of the emission spectra and they were used as input variables for a multiple linear discriminant analysis across different groups. The discriminant analysis classifies 94.7% of the original grouped cases and 94.1% of the cross‐validated grouped cases correctly. Based on the fluorescence emission characteristics of urine and statistical analysis, it may be concluded that the fluorophores nicotinamide adenine dinucleotide (NADH) and flavins may be considered as metabolomic markers of cancer. 相似文献
994.
A facile synthesis of some diketones that fit into a steroid motif was achieved from Mannich salts and cyclic ketones under microwave irradiation. 相似文献
995.
A variety of carbonyl compounds can be easily converted to the corresponding 1,3‐oxathiolanes in the presence of a catalytic amount of tantalum(V) chloride [TaCl5] on silica gel in dichloromethane. Mild reaction conditions, efficiency, high yields, operational simplicity, and only 2.5 mol% of TaCl5 catalyst are some of the major advantages of the procedure. 相似文献
996.
Dichlorine monoxide is a selective reagent for the monochlorination at the active quinonoid position in benzoquinones and naphthoquinones. 相似文献
997.
A one‐pot synthesis of oxime derivatives 3a–3f of 1‐phenyl‐3‐arylpyrazole‐4‐carboxaldehydes has been accomplished by the Vilsmeier–Haack reaction of acetophenone phenylhydrazones 1a–1f under a new workup procedure. 相似文献
998.
Sangeeta Bajpai Prakash Chandra Srivastava 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):1077-1085
Abstract A series of 1,3-dihydro-2λ4-benzotellurole-2,2-diyl di-thiocarbamates C8H8TeR2 and C8H8TeIR ( R═ S 2CNC5H10, S2CNHC6H5, S2CNC4H8O) have been synthesised by the reactions of C8H8TeI2 with the corresponding ammonium salts of piperidine-, aniline- and morpholine- dithiocarbamates in 1:1 and 1:2 molar ratio, respectively. They have been characterized by FT-IR and (1H, 13C) NMR spectroscopy. The reaction of C8H8TeI2 with (NH4S2CNC5H10) in 1:2 molar ratio gives C8H8Te(S2CNC5H10)2 [IR, (1H, 13C)NMR evidence] and X-ray quality crystals of Te(S2CNC5H10)2 in very low yield, demonstrating the formation of the first Te–C bond-cleaved product.The monomers of Te(S2CNC5H10)2 are connected through intermolecular Te…S secondary bonds and it exists as a dimer in the solid state. These dimers are interconnected through intermolecular S…S secondary bonds to yield 3D-supramolecular network. 相似文献
999.
Mari Sithambaram Karthikeyan Manjathuru Mahalinga Prakash Karegoundar Boja Poojary Bantwal Shivarama Holla 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):3231-3240
A series of 7-substituted arylidene-1,3-thiazolo[2,3-c]-1,2,4-triazine-4,6-diones were synthesized in an one-pot multicomponent reaction of 6-arylmethyl-3-mercapto-1,2,4-triazin-5-ones with substituted benzaldehydes and monochloroacetic acid in the presence of acetic anhydride, acetic acid, and sodium acetate. The structures of the new compounds were supported by IR, 1H NMR, MS, and analytical data. All the new compounds were tested for their antibacterial and antifungal activity. Arylidene thiazolo triazinediones with 1,3-benzodioxolo substituent at seventh and p-chlorophenyl or 2,4-dichlorophenyl substituents at third displayed good antibacterial and antifungal activity. And also compound bearing 2,3,5-trimethoxyphenyl substituent at seventh and 2,4-dichlorophenyl substituent at third displayed good activity. 相似文献
1000.
Sanjiv Arora Deepak K. Aneja Mahesh Kumar Chetan Sharma Om Prakash 《Journal of Thermal Analysis and Calorimetry》2013,111(1):17-25
A series of new unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles (3a–d) has been synthesized to evaluate their antibacterial and thermal properties. All compounds have been tested for their in vitro antibacterial activity against two Gram-positive bacteria namely, Staphylococcus aureus and Bacillus subtilis. Among the tested compounds, compound 2-(4-chlorophenyl)-5-(thiophen-2-yl)-1,3,4-oxadiazole (3c) has been found to be most potent member having minimum inhibitory concentration. Thermal stability and melting point of compounds have been studied by TG and DSC analysis in air atmosphere at heating rate of 10 °C min?1. Thermal degradation kinetics of the most potent antibacterial compound 3c has been carried out by multiple heating rate model free kinetic methods namely, Ozawa–Flynn–Wall, modified Coats-Redfern, and Kissinger. 相似文献