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1.
Several N,N-diethyl-tert-alkylamines, such as N,N-diethyl-2-methyl-2-butylamine (1, t-PentNEt2), N,N-diethyl-2,3-dimethyl-2-butylamine (2, t-HexNEt2), N,N-diethyl-2,3,3-trimethyl-2-butylamine (3, t-HeptNEt2), and N,N-diethyl-1,1,3,3-tetramethylbutylamine (4, t-OctNEt2) with varying steric bulk around nitrogen (by changing the tert-alkyl group) have been prepared and examined as borane carriers. The complexing ability of these N,N-diethyl-tert-alkylamines with borane decreases in the order: t-BuNEt2 > t-PentNEt2 > t-HeptNEt2 > t-HexNEt2 > or = t-OctNEt2. From these preliminary studies, the more promising tert-octyldialkylamines were selected for detailed studies. The optimum steric bulk around the nitrogen atom was established by comparing various tert-octyldialkylamines containing variable steric requirements for both the alkyl groups. The complexing ability of these amines with borane decreases in the order shown: t-OctNMe2 (5) > t-OctNEtMe (6) > t-OctN-(CH2CH2)2O (7) > t-OctNEt2 (4) > t-OctNBuiMe (8) > t-OctNPr(n)2 (9). The reactivity of the corresponding borane adducts toward 1-octene increases in the reverse order. Among the various tert-octyldialkylamine-boranes prepared and examined, only t-OctNEt2 (4) forms a highly reactive liquid borane adduct, which hydroborates 1-octene in tetrahydrofuran rapidly at room temperature. Accordingly, detailed hydroboration studies with this new, highly reactive amine-borane adduct, t-OctEt2N:BH3 (10) and representative mono-, di-, tri-, and tetra-substituted olefins were carried out at room temperature (22 +/- 3 degrees C) in selected solvents, tetrahydrofuran, dioxane, tert-butyl methyl ether, n-pentane and dichloromethane. Simple unhindered olefins were hydroborated to the trialkylborane stage, whereas hindered olefins were partially hydroborated to the mono or dialkylborane stage. The hydroborations can be carried out conveniently in a variety of solvents. The amine-borane adduct showed enhanced reactivity in dioxane but low reactivity in dichloromethane. The alkylboranes obtained after hydroboration were oxidized with hydrogen peroxide/sodium hydroxide and the product alcohols were obtained in quantitative yields, as established by GC analysis. The carrier amine was recovered by simple acid-base manipulations in good yield and can be readily recycled back to the borane adduct. 相似文献
2.
S. Ravi Kanth D. Maitraie P. Shanthan Rao B. Sridhar 《Journal of fluorine chemistry》2006,127(9):1211-1221
Three-component Grieco condensation reaction of 3-aminopyrazolo[3,4-b]pyridine, formaldehyde/benzaldehyde and electron rich alkenes in presence of iron(III) chloride gave tetrahydropyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines/quinazolines in single pot. The sequence of reactions is formation of di-azadiene in situ and the subsequent regioselective addition of alkenes in aza-Diels Alder type reaction. The structure and stereochemistry of the products were confirmed by spectral data and single crystal X-ray crystallography. 相似文献
3.
Terminal alkynes and alkenes were conveniently hydroborated to the corresponding alkenyl- and alkyldichloroboranes using dichloroborane-dioxane in dichloromethane. These dichloroboranes were hydrolyzed by water to the corresponding alkenyl- and alkylboronic acids in moderate to good yields. With terminal alkenes and alkynes boron was predominantly attached to terminal carbon. Alkynes gave exclusively trans-vinylboronic acids. 相似文献
4.
Abstract A biocompatible zinc (II) complex based on a tetradentate N,N,O,O-type salen ligand was synthesized, characterized and used for the solvent-free ring-opening polymerization (ROP) of L-lactide in bulk at 180?°C to prepare high molecular weight poly(L-lactide) (Mn : 82,600?Da; Mw : 140,000?Da; PDI: 1.70). Poly(L-lactide) (PLLA) was characterized using FTIR, 1H NMR, 13C NMR, GPC, TGA, DSC, WAXD, and MALDI-ToF. Kinetic measurement was carried out and first-order behavior to monomer was observed. The k app was found as 6?±?0.001?×?10?4?s?1. The biocompatibility of the PLLA was confirmed by in vitro cytotoxicity against NIH/3T3 fibroblast cell line and can be used in biomedical applications. 相似文献
5.
Chen Hui Sharma Sunil K. Sharma Priyanka R. Chi Kai Fung Eric Aubrecht Katherine Keroletswe Ngonye Chigome Samuel Hsiao Benjamin S. 《Cellulose (London, England)》2021,28(13):8611-8628
Cellulose - Mercury contamination in drinking water is a worldwide problem due to its severely harming effects on the human body. A nanostructured natural bioadsorbent, carboxycellulose nanofiber... 相似文献
6.
Mixed Polymer‐Coated Magnetic Nanoparticles as Forward Osmosis Draw Agents of Tuned Hydrophilicity 下载免费PDF全文
Dr. Priyanka Dey Dr. Emad L. Izake 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11253-11260
We recently reported a polymer‐coated magnetic nanoparticle (MNP) draw agent for the forward osmosis (FO) water desalination process. The water flux was found to increase when the polymer poly(sodium acrylate) (PSA) was anchored to the MNP surface as compared to the polymer (or polyelectrolyte solution) alone, due to the polymer chains being stretched out and most of the hydrophilic groups on the polymer contributing to water flux. We herein report the use of a secondary polymer poly(N‐isopropylacrylamide) PNIPAM to manipulate the PSA polymer conformation and influence inter‐ and intrachain interactions to enhance the efficiency of the FO draw agent. These PSA–PNIPAM‐coated MNPs generated a much higher water flux of ~11.66 LMH when compared to the 100 % PSA‐coated MNPs featuring a value of ~5.32 LMH under identical FO conditions. The osmotic pressure and water flux driven by the mixed polymer‐coated MNPs were found to be a strong function of the net polymer coverage on MNPs, that is, net available hydrophilic groups. Our new draw agent demonstrates potential for use in the water industry due to its improved efficiency and cost effectiveness as it uses only ~0.062 % (w/v) of the draw agent solution. 相似文献
7.
In this work, we prove the weak and strong convergence of a sequence generated by a modified S-iteration process for finding a common fixed point of two G-nonexpansive mappings in a uniformly convex Banach space with a directed graph. We also give some numerical examples for supporting our main theorem and compare convergence rate between the studied iteration and the Ishikawa iteration. 相似文献
8.
Simultaneous quantification of atenolol and chlorthalidone in human plasma by ultra‐performance liquid chromatography–tandem mass spectrometry 下载免费PDF全文
Jaivik V. Shah Daxesh P. Patel Priyanka A. Shah Mallika Sanyal Pranav S. Shrivastav 《Biomedical chromatography : BMC》2016,30(2):208-216
A simple, sensitive and reproducible ultra‐performance liquid chromatography–tandem mass spectrometry method has been developed for the simultaneous determination of atenolol, a β‐adrenergic receptor‐blocker and chlorthalidone, a monosulfonamyl diuretic in human plasma, using atenolol‐d7 and chlorthalidone‐d4 as the internal standards (ISs). Following solid‐phase extraction on Phenomenex Strata‐X cartridges using 100 μL human plasma sample, the analytes and ISs were separated on an Acquity UPLC BEH C18 (50 mm × 2.1 mm, 1.7 µm) column using a mobile phase consisting of 0.1% formic acid–acetonitrile (25:75, v/v). A tandem mass spectrometer equipped with electrospray ionization was used as a detector in the positive ionization mode for both analytes. The linear concentration range was established as 0.50–500 ng/mL for atenolol and 0.25–150 ng/mL for chlorthalidone. Extraction recoveries were within 95–103% and ion suppression/enhancement, expressed as IS‐normalized matrix factors, ranged from 0.95 to 1.06 for both the analytes. Intra‐batch and inter‐batch precision (CV) and accuracy values were 2.37–5.91 and 96.1–103.2%, respectively. Stability of analytes in plasma was evaluated under different conditions, such as bench‐top, freeze–thaw, dry and wet extract and long‐term. The developed method was superior to the existing methods for the simultaneous determination of atenolol and chlorthalidone in human plasma with respect to the sensitivity, chromatographic analysis time and plasma volume for processing. Further, it was successfully applied to support a bioequivalence study of 50 mg atenolol + 12.5 mg chlorthalidone in 28 healthy Indian subjects. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
Ovender Singh Priyanka Gupta Anshu Singh Ankur Maji Udai P. Singh Kaushik Ghosh 《应用有机金属化学》2019,33(5)
Hexacoordinated non‐heme iron complexes [FeII(L1)2](ClO4)2 ( 1 ) and [FeII(L2)2](PF6)2 ( 2 ) have been synthesized using ligands L1 = (E)‐2‐chloro‐6‐(2‐(pyridin‐2ylmethylene) hydrazinyl)pyridine and L2 = (E)‐2‐chloro‐6‐(2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinyl) pyridine]. These complexes are highly active non‐heme iron catalysts to catalyze the C (sp3)?H bonds of alkanes. These iron complexes have been characterized using ESI?MS analysis and molecular structures were determined by X‐ray crystallography. ESI ? MS analysis also helped to understand the generation of intermediate species like FeIII?OOH and FeIV=O. DFT and TD?DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes. 相似文献
10.
Priyanka Lohar Manish Kumar Sharma Amit Kumar Sahu Rajeswari Rathod Pinaki Sengupta 《Biomedical chromatography : BMC》2019,33(12)
The combination of acebrophylline (ABP), levocetirizine (LCZ) and pranlukast (PRN) is used to treat allergic rhinitis, asthma, hay‐fever and other conditions where patients experience difficulty in breathing. This study was carried out with the aim of developing and validating a reverse‐phase high‐performance liquid chromatographic bioanalytical method to simultaneously quantitate ABP, LCZ and PRN in rat plasma. The objective also includes determination of the pharmacokinetic interaction of these three drugs after administration via the oral route after individual and combination treatment in rat. Optimum resolution between the analytes was observed with a C18 Kinetex column (250 mm × 4.6 mm × 5 μm). The chromatography was performed in a gradient elution mode with a 1 mL/min flow rate. The calibration curves were linear over the concentration range of 100–1600 ng/mL. The intra‐ and inter‐day precision and accuracy were found to be within acceptable limits as specified in US Food and Drug Administration guideline for bioanalytical method validation. The analytes were stable on the bench‐top (8 h), after three freeze–thaw cycles, in the autosampler (8 h) and as a dry extract (?80°C for 48 h). The statistical results of the pharmacokinetic study in Sprague–Dawley rats showed a significant change in pharmacokinetic parameters for PRN upon co‐administration of the three drugs. 相似文献