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51.
Abhishek Upadhyay Laxmi Kant Sharma Vinay K. Singh Rahul Dubey Narendra Kumar Rana Krishna Pal Singh 《Tetrahedron letters》2017,58(13):1245-1249
An efficient one pot, multicomponent-tandem synthesis of highly functionalized 1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile is reported by electrochemically induced condensation of ethyl acetoacetate, hydrazine hydrate, malononitrile and various aromatic aldehydes. The reaction is carried out in an undivided cell, at a constant current in the presence of NaBr as a supporting electrolyte and ethanol as solvent. 相似文献
52.
Fentanyl is a very potent synthetic narcotic analgesic. Because of its strong sedative properties, it has become an analogue
of illicit drugs such as heroin. Its unambiguous detection and identification in environmental samples can be regarded as
strong evidence of its illicit preparation. In this paper we report application of single-drop microextraction (SDME) for
analysis of water samples spiked with fentanyl. Experimental conditions which affect the performance of SDME, for example
the nature of the extracting solvent, sample stirring speed, extraction time, ionic strength, and solution pH, were optimized.
The method was found to be linear in the concentration range 0.10–10 ng mL−1. The limits of quantitation and detection of the method were 100 pg mL−1 and <75 pg mL−1, respectively. This technique is superior to other sample-preparation techniques because of the simple experimental set-up,
short analysis time, high sensitivity, and minimum use of organic solvent. 相似文献
53.
54.
Synthesis of 1-substituted tetrahydrocarbazole is accomplished by TfOH catalyzed reaction of 3-substituted indoles tethered with secondary and tertiary alcohols. The reaction was generalized for a variety of substrates and was extended to the synthesis of 2,3,3a,6-tetrahydro-1H-pyrido[3,2,1-jk]carbazole and carbazoles. 相似文献
55.
56.
Computational study on the kinetics of OH initiated oxidation of methyl difluoroacetate (CF2HCOOCH3)
The kinetics of hydrogen atom abstraction reactions of methyl difluoroacetate (CF2HCOOCH3) by OH radical has been studied by quantum mechanical method. The geometry optimisation and frequency calculation of the titled compound was performed with density functional theory using hybrid meta density functional MPWB1K with 6-31+G(d,p) basis set. Transition states have been determined and intrinsic reaction coordinate (IRC) calculation has been performed to ascertain that the transition from reactants to products was smooth through the corresponding transition state. Energy values are refined by making single point energy calculation at G3B3 level of theory and an energy level diagram is constructed. The standard enthalpies of formation of reactants and other species formed during the reaction were calculated using isodesmic method. The rate constants are calculated using canonical transition state theory and the overall rate constant is determined to be 1.35×10?13 cm3 molecule?1 s?1 at 298 K and 1 atmospheric pressure. Tunnelling has been taken into account in the determination of the rate constant because it plays a critical role at low temperature especially when transfer of hydrogen takes place. The calculated value is found to be in good agreement with the experimentally determined value of 1.48×10?13 cm3 molecule?1 s?1. 相似文献
57.
Magnetic CuFe2O4 nanoparticles: a retrievable catalyst for oxidative amidation of aldehydes with amine hydrochloride salts 总被引:1,自引:0,他引:1
The application of magnetic CuFe2O4 nanoparticles for the oxidative amidation of aldehydes with amine hydrochloride salts is described. A wide range of amides have been synthesized in good to excellent yields under mild conditions. Chiral amide also synthesized from its corresponding chiral amine salt with retention of the stereochemistry. In particular, the performance of the magnetic separation of the catalyst was very efficient and an alternative to time, solvent and energy-consuming separation procedures. The catalytic activity of the catalyst remains unaltered after five consecutive cycles, making it environmentally benign and widely applicable due to its efficiency, ease of handling and cost effectiveness. 相似文献
58.
Mukesh Kumar Amarnath Chatterjee Anand P. Khedkar Mutyalasetty Kusumanchi Laxmi Adhikary 《Journal of the American Society for Mass Spectrometry》2013,24(2):202-212
Formation of cyclic intermediates involving water or ammonia loss is a common occurrence in any reaction involving terminal amines or hydroxyl group containing species. Proteins that have both these functional groups in abundance are no exception, and presence of amino acids such as asparagine, glutamines, aspartic acids, and glutamic acids aid in formation of such intermediates. In the biopharma scenario, such intermediates lead to product- or process-related impurities that might be immunogenic. Mass spectroscopy is a powerful technique that is used to decipher the presence and physicochemical characteristics of such impurities. However, such intermediates can also form in situ during mass spectrometric analysis. We present here the detection of in-source and in-solution formation of succinimide and pyroglutamate in the protein granulocyte colony stimulating factor. We also propose an approach for quick differentiation of such in-situ species from the tangible impurities. We believe that this will not only reduce the time spent in unambiguous identification of succinimide- and/or pyroglutamate-related impurity in bio-pharmaceutics but also provide a platform for similar studies on other impurities that may form due to stabilized intermediates. 相似文献
59.
G. V. M. Sharma K. Laxmi Reddy P. Sree Lakshmi Palakodety Radha Krishna 《Journal of heterocyclic chemistry》2005,42(7):1387-1391
Stereoselective synthesis of dihydropyrimidinone glycoconjugates in high yields, from different sugar aldehydes, by a three‐component coupling (Biginelli) reaction is reported. In this new method, HC1 generated ‘in situ’ from2,4,6‐trichloro[l,3,5]triazine(TCT; 10 mol%), was used under mild and solvent free reaction conditions. 相似文献
60.
B. Suresh Kuarm J. Venu Madhav S. Vijaya Laxmi Y. Thirupathi Reddy P. Narsimha Reddy 《合成通讯》2013,43(12):1719-1724
A series of 1-oxo-hexahydroxanthene derivatives was synthesized at room temperature in solid state from substituted salicylaldehydes and substituted 1,3-hexanediones in the presence of a catalytic amount of cellulose sulfuric acid. The results showed that the reaction performed under solid-state conditions was benign to the environment, with higher yields and more convenient workup.