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91.
92.
Dr. Chetan Kumar Arya Swati Yadav Dr. Jonathan Fine Dr. Ana Casanal Dr. Gaurav Chopra Prof. Dr. Gurunath Ramanathan Dr. Kutti R. Vinothkumar Prof. Dr. Ramaswamy Subramanian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17109-17114
N,N-dimethyl formamide (DMF) is an extensively used organic solvent but is also a potent pollutant. Certain bacterial species from genera such as Paracoccus, Pseudomonas, and Alcaligenes have evolved to use DMF as a sole carbon and nitrogen source for growth via degradation by a dimethylformamidase (DMFase). We show that DMFase from Paracoccus sp. strain DMF is a halophilic and thermostable enzyme comprising a multimeric complex of the α2β2 or (α2β2)2 type. One of the three domains of the large subunit and the small subunit are hitherto undescribed protein folds of unknown evolutionary origin. The active site consists of a mononuclear iron coordinated by two Tyr side-chain phenolates and one carboxylate from Glu. The Fe3+ ion in the active site catalyzes the hydrolytic cleavage of the amide bond in DMF. Kinetic characterization reveals that the enzyme shows cooperativity between subunits, and mutagenesis and structural data provide clues to the catalytic mechanism. 相似文献
93.
Chetan K. Jadhav M.Sc NET Amol S. Nipate M.Sc NET Asha V. Chate Ph.D. Anil P. Patil Ph.D. Charansingh. H. Gill Ph.D. Professor 《Journal of heterocyclic chemistry》2020,57(12):4291-4303
The synthesis of a combinatorial library of heterocycle-fused pyridine derivatives has been achieved successfully via a one-pot four-component reaction of aromatic/aliphatic aldehyde, malononitrile, thiazolidine-2,4-dione and ammonium acetate in the presence of piperidinium acetate as the catalyst. It involved the Knoevenagel condensation of the aldehyde and malononitrile to produce arylidene malononitrile as an intermediate, which was further intramolecular cyclization through Michael type addition ketone to the electrophilic double bond of the arylidene to produce fused pyridines in high yields. Environmental friendliness, low cost, Operational simplicity, extensive reusability and applicability, and easy recovery of the catalyst using simple evaporation are the critical features of this methodology. Also, a series of pyridine based dihydrothiazolo[4,5-b] pyridine-6-carbonitrile analogs were synthesized and selected for their in vitro antifungal and antibacterial activities. 相似文献
94.
An efficient, and environmentally benign protocol for a three-component Kabachnik-Fields reaction of aldehydes, amines, and diethyl phosphite catalyzed by sulfated polyborate has been described to afford α-amino phosphonates under solvent-free reaction conditions. The major advantages of the present method are high yields, short reaction time, simple work-up procedure, inexpensive, eco-friendly and reusable catalyst and solvent-free reaction conditions and tolerance towards various functional groups present in the substrates. 相似文献
95.
The excellent catalytic potential of sulfated polyborate is utilized in the synthesis of (un)symmetrical ureas and benzimidazolones by heating amines or substituted OPDA and urea or N-phenylureas under a solvent-free condition at 120?°C is described. The key advantages of the present protocol are phosgene-free, and other hazardous reagents or organic solvent free, high reaction rates and yields, simple workup procedure, and recyclability of the catalyst. 相似文献
96.
A Facile Synthesis of Some New 1‐Benzothiazolyl‐3‐aryl/Hetaryl‐5‐(3‐aryl‐1‐phenyl‐4‐pyrazolyl) Pyrazoles and Their Antimicrobial Activity
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Sushma Singh Vijaykiran Punia Chetan Sharma K. R. Aneja Om Prakash Rashmi Pundeer 《Journal of heterocyclic chemistry》2015,52(6):1817-1822
Some new derivatives of 1‐benzothiazolyl‐3‐aryl/hetaryl‐5‐(3‐aryl‐1‐phenyl‐4‐pyrazolyl) pyrazoles were synthesized by the cyclocondensation of 1‐aryl/hetaryl‐3‐(3‐aryl‐1‐phenyl‐1H‐pyrazole‐4‐yl)prop‐2‐en‐1‐ones (pyrazolyl chalcones) and 6‐substituted‐2‐hydrazinobenzothiazoles. 相似文献
97.
A simple and efficient method for the synthesis of four-component 1,4-dihydropyridines of various aldehydes, β-ketoesters and ammonium carbonate catalyzed by sulfated polyborate with high yields under a solvent free condition at 90 °C is described. The key advantages of the present method are high yields, short reaction time, solvent free condition, easy workup, recyclability of catalyst and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards. 相似文献
98.
James J. Powers David A. Favor Trent Rankin Chetan Pandit Samarendra N. Maiti 《Tetrahedron letters》2009,50(12):1267-731
The synthesis of a series of methyl-, fluoro-, and chloro-substituted 6-hydroxyisoindolin-1-ones is described. 相似文献
99.
Chetan K. Modi Parthiv M. Trivedi Jiten A. Chudasama Haresh D. Nakum Digvijaysinh K. Parmar Sanjeev K. Gupta 《Green Chemistry Letters and Reviews》2014,7(3):278-287
The intriguing research toward the exploitation of zeolite-Y-based hybrid nanocatalysts for catalytic oxidation reactions has been growing significantly. In the present investigation, we describe the synthesis of zeolite-Y entrapped transition metal complexes of the general formulae [M(SFCH)·xH2O]-Y (where, M = Mn, Fe, Co, Ni (x = 3) and Cu (x = 1)); H2SFCH = (E)-N′-(2-hydroxybenzylidene)furan-2-carbohydrazide]. These nanocatalysts have been characterized by various physicochemical techniques. Density functional theory calculations are performed to address the relaxed geometry, bond angle, bond length, dihedral angle, highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap, and electronic density of states of H2SFCH ligand and their neat transition metal complexes. The observed HOMO–LUMO gap and the Fermi energy is higher for Cu(II) complexes, which demonstrates the better catalytic activity of this nanocatalyst. The catalytic activity was performed in liquid-phase oxidation of cyclohexane using hydrogen peroxide as oxidant to give cyclohexanone (CyONE) and cyclohexanol (CyOL). Among them, [Cu(SFCH)·H2O]-Y catalyst has the highest selectivity toward CyONE (84.5%). 相似文献
100.
Chetan Nayak 《General Relativity and Gravitation》1991,23(6):661-669
We consider the loop space representation of Rovelli and Smolin as the starting point for the analysis of quantum gravity in 2+1 dimensions. To do so, we introduce observables directly within this representation and consider the problem of its Lagrangian formulation. The implications of this framework for the issue of time are discussed and the extension of these results to 3+1 gravity is also considered. 相似文献