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Scheme 32. Suggested mechanism for ceric ammonium nitrate (CAN) catalyzed sonochemical synthesis of DHPM(s) (102).
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In the recent years, being dedicated on green chemistry using environmentally benign reagents and conditions is one of the most fascinating developments in synthesis of widely used organic compounds. This review describes the theory and importance of ultrasound as an efficient tool in the synthesis of heterocyclic compounds.
Citations
... The reluctance to utilize DIUH in organic synthesis is due to the tremendous energy released, which is incompatible with the covalent bonds found in organic molecules; therefore, it will be modified to use just 25% of its power if used [15]. Furthermore, when it is used in organic synthesis, the titanium tip of the horn undergoes erosion, raising a cautionary limitation for this type [16]. The third kind of reactor is the ultrasonic probe cup horn, which is mostly used to remove organic contaminants from water (for wastewater treatment) [17,18]. ...
The development of a mild, general, and green method for the C-H arylation of pyrazoles with relatively unreactive aryl halides is an ongoing challenge in organic synthesis. We describe herein a novel sonophotoreactor based on an ultrasonic cleaning bath and blue LED light (visible light) that induce copper-catalyzed monoarylation for pharmacologically relevant pyrazoles. The hybrid effect of ultrasonic irradiation and blue LED is discussed to interpret the observed synergistic action. A broad array of pyrazoles coupled with iodobenzene avoids expensive palladium metal or salts, and certain designed substrates were attained. Only comparatively inexpensive copper(I)iodide and 1,10-phenanthroline were used all together as the catalyst. The presented technique is a greener way to create C-H arylation of pyrazoles. It significantly reduces the amount of energy needed.
... The Vibra Cell VC 505 consisted of a processor, a titanium sonotrode, and the process control unit. Lead zirconate titanate piezoelectric material act as an ultrasonic transducer that contracts, expands, and subsequently converts electric energy to sound energy through a titanium horn (probe) [23]. A VWR 1156 recirculating chiller obtained from VWR Scientific was used to maintain the temperature at 5 • C (25 • C cell temperature) and a PowerSpin FX centrifuge purchased from Unico Scientific with a spin rate of 3400 rpm was used to centrifuge the reaction mixture. ...
Biodiesel, a mixture of fatty acid methyl esters (FAME), is bio-renewable, non-toxic, biodegradable, and is an attractive alternative to petroleum diesel. This work studied the sonochemical transesterification of Lesquerella fendleri oil (LFO) using inexpensive solid Lewis acid (LA) catalysts with an aim to reduce environmental pollution and dependance on non-renewable fuel sources. Due to the presence of hydroxy fatty acid methyl esters (HFAME) in LFO (∼60%), in addition to producing biofuel it can also be used to generate chemically important estolides and cyclic lactones. AlCl3, SnCl2, and Sn(CH3COO)2 showed catalytic activity using direct immersion ultrasound (DI-US) among a list of LA catalysts investigated, with AlCl3 being the best catalyst. Ultrasound increased the reaction rate by facilitating carbocation formation of glyceridic carbons. Experiments were carried out at room temperature in a solvent range from 3:1 to 18:1 methanol-to-oil molar ratio and catalyst loading from 1 wt.% to 6 wt.% over 10 to 60 min sonication time at 48% ultrasound amplitude (roughly 17 W/cm²). Complete conversion (>99%) was achieved in 40 min with 5 wt.% AlCl3 catalyst. A statistical regression analysis with STATA 14.0 software was performed to optimize process parameters. Chemical characterizations of the compounds were performed with nuclear magnetic resonance (NMR) spectroscopy (¹H NMR & ¹³C NMR), and % conversion of FAMEs was calculated from the ¹H NMR spectra. The fatty acid profile was determined by GC-FID and GC-MS analysis. FT-IR spectroscopic analysis and thermogravimetric analysis (TGA) were performed to investigate the infrared absorption pattern of the compound and the volatility difference between Lesquerella fendleri biodiesel and oil under nitrogen atmosphere. Results indicate that this is a fast, green, energy-efficient, sustainable, and industrially applicable method for biodiesel production from LFO.
... The application of ultrasound to promote radical reactions and capture the radicals for synthetically producing heterocycles is a scarce research topic. The synthesis of bioactive compounds has also been improved by the advantages of ultrasound, and ultrasound has become an attractive tool for the improvement and discovery of protocols to produce heterocycles [25,26], including molecules of pharmaceutical interest [27]. ...
Novel functionalized indolines were synthesized from 2-(((N-aryl)amino)methyl)acrylates and formamides under ultrasonic irradiation for the first time. Aiming to develop a straightforward and easy-to-implement methodology for the synthesis of indolines, an instrumentation setup was designed, including ultrasound (US) equipment (Ultrasonic Horn; tip diameter of 12.7 mm, 20 kHz, maximum power of 400 W), an open reaction flask, and an inexpensive and green catalyst (1 mol%; FeSO4.7H2O; CAS: 7782-63-0) without the need for anhydrous conditions. The use of the sono-Fenton process in the presence of formamides and 2-(((N-aryl)amino)methyl)acrylates afforded a broad range of functionalized indolines within 60 seconds in high yields. Several experimental parameters of the ultrasound-assisted reaction were evaluated, such as amplitude (40-80%), sonication time (15-60 s), and pulsed ultrasonic irradiation. A 60 s silent reaction did not produce the desired indoline. The optimized conditions for US-mediated reactions allowed the production of functionalized indolines in high isolated yields (up to 99%, 60 s reaction, pulse ration 1 s:1 s, US amplitude 60 %)
... The short-lived chemical species are turned back to the bulk liquid and react with other species [32]. Sometimes homogeneous sonochemistry followed by secondary reactions taking place in the liquid, especially in the case of compounds of low volatility, which can interact with radical species produced from solvent sonolysis [33]. In homogeneous systems, where the surroundings are uniform, the cavity remains spherical. ...
Lignocellulosic biomass represents a natural renewable chemical feedstock that can be used to produce high value-added chemicals and platform molecules. Nowadays, there are extensive studies on a variety of aspects concerning the valorization of lignocellulosic biomass into desirable products. Among the current technologies for biomass conversion some require extreme conditions along with high temperatures and pressures. Therefore, major technological innovations based on more economical and environmental methodologies are currently developed both in academic laboratories and in industry. In this context, ultrasound-assisted catalysis constitutes an alternative method offering new strategies to upgrade biomass. The possibility of combining catalysis with sonication indeed provides avenues that are worth exploring for the valorization of lignocellulosic compounds into value-added chemical feedstocks. In this mini-review, the available sonochemical systems are first presented, with a focus on the most important ultrasonic parameters, which is intended to provide a mechanistic background. Next, this contribution aims to provide insight into the most recent developments along with prominent examples in the field of sonocatalysis applied to the chemical transformation of lignocellulosic biomass and its derivatives.
Graphical Abstract
... In this connection, devising smart but simple synthetic protocols which are also in sync with the current idea of sustainable chemistry is an important aim of a synthetic chemist [10]. Sonochemistry or the use of ultrasonic irradiation to activate organic reactions is one such innovative and smart strategy of contemporary organic synthesis [11]. Repetitive use of several important drugs has triggered resistance in many pathogens and multidrug-resistant strains of bacteria and fungi have emerged in the past few decades. ...
... The synthesized compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) [17]. The procedure was adopted from our previous work [18]. ...
... The synthesis of substituted amino oxadiazole (1-4) and their imino derivatives (5)(6)(7)(8)(9)(10)(11)(12) was accomplished according to the steps illustrated in • ▶ Fig. 1. Commercially available carboxylic acid (benzoic/salicylic/p-Cl-benzoic/cinnamic) and semicarbazide were ground together in a mortar and subsequently refluxed [15] in conc. ...
A facile synthesis of 2-substituted-5-amino-oxadiazole derivatives has been achieved by refluxing/sonicating a mixture of semicarbazide with various aromatic acids in conc. sulphuric acid alone. The isolated products were further condensed with p-dimethylaminobenzaldehyde/p-hydroxybenzaldehyde to obtain respective imino derivatives. Finally, some potentially biologically active imidazole analogues were obtained by reacting ammonium acetate and 5-bromoisatin with the synthesized imino products. All the newly synthesized compounds were thoroughly characterized by standard analytical techniques. These imidazole-oxadiazole hybrid compounds were also evaluated for their antimicrobial and antimalarial activities. The compounds all exhibited moderate to significant antimicrobial activity (6-10 mm, zone of inhibition) and promising antimalarial activity (IC50 0.037-0.100 µM). This report entails a detailed synthetic procedure, spectroscopic elucidation and activities of the synthesized compounds.
© Georg Thieme Verlag KG Stuttgart · New York.
Thiadiazole is a paradigm of five membered heterocyclic compound that contains two nitrogens and one sulphur as heteroatoms with molecular formula C2H2N2S. Thiadiazole is mainly present in four isomeric forms such as 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole and 1,3,4-thiadiazole. Out of these isomers, 1,3,4-thiadiazole has attracted remarkable attention in the field of medicinal chemistry. Some of the drugs containing 1,3,4-thiadiazole moiety are used clinically and are available in the market including Sulphamethizole (Antibacterial), Acetazolamide (Diuretic), Azetepa (Antineoplastic), Cefazolin (Antibiotic), Megazol (Antiprotozoal), Atibeprone (anti-depressant). Several greener approaches are applied for the synthesis of thiadiazole scaffolds including microwave irradiation, ultrasonic irradiation, grinding, ball milling technique, etc. These methods are eco-friendly, nonhazardous, reproducible, and economical approach. Based on these Green chemistry approaches, thiadiazole derivatives are synthesized from thiosemicarbazide. The functionalization of these heterocyclic compounds generates thiadiazole derivatives with diverse chemical structures. This review covers green synthesis, biological potentials, and structure activity relationship study of thiadiazole analogs.
Polyoxyethylenated stearyl ether maleic acid diesters (PSME-n) have been synthesized through esterification of maleic anhydride and polyoxyethylenated stearyl ether (n) (PSE-n) using an ultrasonic-microwave technique. The resulting products were characterized by FTIR and 1H-NMR. Inference of the reaction conditions, such as microwave power, ultrasonic power, temperature and reaction time, were evaluated. The optimal conditions are as follows: n PSE: n MA = 2:1, catalyst p-toluene sulphonic acid (TsOH) 3 %, reaction temperature 130 °C, microwave power 400 W, ultrasonic power 180 W and reaction time 60 min. Under the optimal conditions, the esterification rates of the series of products have reached up to 89-92 %. The results showed that the ultrasonic-microwave technique is able to greatly shorten the time and reduce the temperature of this esterification reaction. The surface properties, particle size and morphology of the micelles of PSE-15 and PSME-15 were investigated by surface tensiometer and FESEM.
An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate, and primary aromatic amine with nanostructure Fe-Cu/ZSM-5 bimetallic oxides in water under ultrasonic irradiation. The short reaction time, good yields, environmental friendly procedure, mild reaction conditions, and convenient operation are important advantage of this protocol. The products generated during the study have been utilized as substrates for synthesis of organosilicon-containing imidazoles. Synthesis of tris(triorganosilyl)methylimidazole derivatives were carried out using organolithium reagent (Me3Si)3CLi, prepared via metalation of (Me3Si)3CH with methyllithium in tetrahydrofuran, in excellent yields.
