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161.
Ultrasound is an essential technique to improve organic synthesis from the point of view of green chemistry, as it can promote better yields and selectivities, in addition to shorter reaction times when compared to the conventional methods. Heterogeneous catalysis is another pillar of sustainable chemistry being the recycling and reuse of the catalysts one of its great advantage. In the other hand, multicomponent reactions provide the synthesis of structurally diverse compounds, in a one-pot fashion, without isolation and purification of intermediates. Thus, the combination of these protocols has proved to be a powerful tool to obtain biologically active organic compounds with lower costs, time and energy consumption. Herein, we provide a comprehensive overview of advances on methods of organic synthesis that have been reported over the past ten years with focus on ultrasound-assisted multicomponent reactions under heterogeneous catalysis. In particular, we present pharmacologically important N- and O-heterocyclic compounds, considering their synthetic methods using green solvents, and catalyst recycling. 相似文献
162.
This study evaluated the application of ultrasound alone or combined with chlorine dioxide (ClO2) for Salmonella Typhimurium and Escherichia coli inactivation in poultry processing chiller tank water. A Full Factorial Design (FFD) 22 was conducted for each microorganism to evaluate the effect of ultrasound exposure time (x1: 1 to 9 min; fixed: 37 kHz; 330 W; 25 °C) using a bath, and ClO2 concentration (x2: 1 to 17 mg L−1) on microorganism count expressed in log CFU mL−1 in distilled water. Variable x2 had a negative effect on Salmonella Typhimurium (-5.09) and Escherichia coli (-2.00) count, improving the inactivation; while a x1 increase present no inactivation improvement, explaining the use of x1 lower level (1 min) and x2 higher level (17 mg L−1). The best condition for microorganism inactivation based on FFD was evaluated in chiller tank water (with organic matter) at 25, 16, and 4 °C; x1 was kept (1 min), however x2 was adjusted to obtain the same residual free chlorine (2.38 mg L−1) considering the ClO2 consumption by organic matter, achieving the value of 30 mg L−1. An inactivation of 49% and 31% were observed for Salmonella Typhimurium and Escherichia coli. When ultrasound was replaced by a simple agitation in the presence of ClO2, there was no inactivation for both microorganisms. Moreover, at poultry carcass pre-chilling (16 °C) and chilling (4 °C) conditions, the synergism of ultrasound combined with ClO2 was more pronounced, with microorganisms’ reductions up to 100%. 相似文献
163.
Ultrasound (US) has become one of the most important techniques in green chemistry and emerging technologies. Many research investigations documented the usefulness of US in a wide range of applications in food science, nanotechnology, and complementary medicine, where effective extraction of natural products is important. However, as with all novel technologies, US has advantages and limitations that require clarification for full adaptation at an industrial scale. The present review discusses recent applications of US in herbal phytochemistry with the emphasis on US effects on chemical structures of bioactive compounds extracted from herbs and their bioactivities. The impact of different US processing conditions such as frequency, intensity, duration, temperature, and pressure on the effectiveness of the extraction process and the properties of the extracted materials are also discussed. Different frequencies and intensities of US have demonstrated its potential applications in modifying, determining, and predicting the physicochemical properties of herbs and their extracts. US has important applications in nanotechnology where it supports the fabrication of inexpensive and eco-friendly herbal nanostructures, as well as acoustic-based biosensors for chemical imaging of the herbal tissues. The application of US enhances the rates of chemical processes such as hydrolysis of herbal fibers, which reduces the time and energy consumed without affecting the quality of the final products. Overall, the use of US in herbal science has great potential to create novel chemical constructions and to be used as an innovative diagnostic system in various biomedical, food, and analytical applications. 相似文献
164.
《Tetrahedron letters》2017,58(25):2498-2502
A new efficient method has been reported for the synthesis of azides by direct azidation of alcohols with TMSN3 in presence of recyclable task specific ionic liquid (TSIL) [bmim]ZnCl3 as a catalyst in DCM at room temperature. Ionic liquid [bmim]ZnCl3 was synthesized under solvent free conditions and characterized by IR, 1H NMR, 13C NMR and HRMS. The Lewis acidity of catalyst was also examined using IR spectroscopy. The main features of this new methodology are high yields of products, recyclability of catalyst, scalability of reaction to gram scale and short reaction time. 相似文献
165.
An eco-friendly tandem tosylation/Ferrier N-glycosylation of amines catalyzed by Er(OTf)3 in 2-MeTHF
Monica Nardi Natividad Herrera Cano Antonio De Nino Maria Luisa Di Gioia Loredana Maiuolo Manuela Oliverio Ana Santiago Diletta Sorrentino Antonio Procopio 《Tetrahedron letters》2017,58(18):1721-1726
Er(OTf)3 in 2-MeTHF provides a new and eco-friendly process for Ferrier glycosylation of sulfonamides and amino acids with various N-nucleophiles.The stereoselective synthesis of 2,3-unsaturated-N-pseudoglycals was carried out with 3,4,6-tri-O-acetyl-d-glucal and different nucleophiles affording good results in a short time. 相似文献
166.
《中国化学会会志》2017,64(9):1035-1040
Here we report the effect of microwave treatment on a silica–carbon (SiO2 /C) filler derived from rice husk and the function of the microwave‐treated filler in an epoxy matrix for electronic packaging applications. Thermogravimetric analysis revealed improved thermal stability of the SiO2 /C filler upon microwave treatment. X‐ray diffraction analysis indicated partial SiC formation after the microwave treatment. For packaging applications, compared to that of the pure epoxy polymer, the thermal conductivity of the epoxy–SiO2 /C composite was improved by 178% at 40 wt % content of the microwave‐treated SiO2 /C filler. Furthermore, an improvement of 149% in storage modulus and 17.6°C in glass transition temperature of the epoxy–SiO2 /C composites was realized. The improvement in thermal stability of SiO2 /C filler could be achieved via a simple microwave treatment, which in turn enhanced the thermal stability, thermal conduction, and thermomechanical strength of the electronic packaging materials. 相似文献
167.
Surabhi Gupta Popuri Sureshbabu Adesh Kumar Singh Shahulhameed Sabiah Jeyakumar Kandasamy 《Tetrahedron letters》2017,58(10):909-913
A simple and efficient method for the deoxygenation of amine N-oxides to corresponding amines is reported using the green and economical reagent phenylboronic acid. Deoxygenation of N,N-dialkylaniline N-oxides, trialkylamine N-oxides and pyridine N-oxides were achieved in good to excellent yields. The reduction susceptible functional groups such as ketone, amide, ester and nitro groups are well tolerated with phenylboronic acid during the deoxygenation process even at high temperature. In addition, an indirect method for identification and quantification of tert-amine N-oxide is demonstrated using UV–Vis spectrometry which may be useful for drug metabolism studies. 相似文献
168.
Pradeep K. Jaiswal Vashundhra Sharma Jaroslav Prikhodko Irina V. Mashevskaya Sandeep Chaudhary 《Tetrahedron letters》2017,58(22):2077-2083
For the first time, an efficient, simple, synthetic green protocol for the one-pot synthesis of functionalized 2-oxo-benzo[1,4]oxazines 24–29 in water under ultrasound irradiation is presented. As compared to conventional methods, the present protocol avoids traditional chromatography and purification steps and furnished the target molecules in excellent yields (upto 98%) with no side products. The methodology was also demonstrated on gram scale synthesis. Moreover, functionalized 2-oxo-quinoxaline analogues 31–33, another class of bio-active heterocyclic scaffolds, were also prepared using this method. For the first time, this protocol was successfully applied in the synthesis of the anticancer indole alkaloid, Cephalandole A 35. 相似文献
169.
Ashish Kumar Yahya E. Jad Ayman El-Faham Beatriz G. de la Torre Fernando Albericio 《Tetrahedron letters》2017,58(30):2986-2988
Herein, we report the use of γ-valerolactone (GVL) and N-formylmorpholine (NFM) as DMF substitutes in polystyrene based SPPS. The solubility of selected amino acids and coupling reagents were studied in GVL and NFM, followed by their use in the successful synthesis of Aib-enkephalin pentapeptide (H-Tyr-Aib-Aib-Phe-Leu-NH2) and Aib-ACP decapeptide (H-Val-Gln-Aib-Aib-Ile-Asp-Tyr-Ile-Asn-Gly-NH2). 相似文献
170.
《Electrophoresis》2017,38(9-10):1334-1343
An analytical methodology based on coprecipitation‐assisted coacervative extraction coupled to HPLC‐UV was developed for determination of five organophosphorus pesticides (OPPs), including fenitrothion, guthion, parathion, methidathion, and chlorpyrifos, in water samples. It involves a green technique leading to an efficient and simple analytical methodology suitable for high‐throughput analysis. Relevant physicochemical variables were studied and optimized on the analytical response of each OPP. Under optimized conditions, the resulting methodology was as follows: an aliquot of 9 mL of water sample was placed into a centrifuge tube and 0.5 mL sodium citrate 0.1 M, pH 4; 0.08 mL Al2(SO4)3 0.1 M; and 0.7 mL SDS 0.1 M were added and homogenized. After centrifugation the supernatant was discarded. A 700 μL aliquot of the coacervate‐rich phase obtained was dissolved with 300 μL of methanol and 20 μL of the resulting solution was analyzed by HPLC‐UV. The resulting LODs ranged within 0.7–2.5 ng/mL and the achieved RSD and recovery values were <8% (n = 3) and >81%, respectively. The proposed analytical methodology was successfully applied for the analysis of five OPPs in water samples for human consumption of different locations of Mendoza. 相似文献