Microwave-assisted Solvent-free Synthesis Research Articles

Process intensification in microwave assisted lipase catalysed solvent-free synthesis of n-nonyl caprylate

Microwave-assisted solvent free synthesis is a frequently applied mainstream tool in various enzymatic processes. Microwaves are a non-contact heat source which reduces the thermal gradient and helps to accelerate energy transfer. Microwave irradiation along with solvent free synthesis has great efficiency and efficacy in product synthesis and purification. In the present investigation, synthesis of n-nonyl caprylate was achieved by using immobilized lipases specifically Lypozyme TLIM, Novozym 435 and Lypozyme RM IM. Novozym 435 (Cal-B) was the best among these catalysts. Highest conversion of 76.8 % was achieved with following parameters: 180 min, 50 °C, 400 rpm, 50 W, 8.36 g/L catalyst loading, and 1:1 mol ratio of caprylic acid to n-nonanol. The confirmation of the product was done by GC-MS analysis.

Microwave-assisted Solvent-free Synthesis of Some New 4-[2-(Substituted phenyl)-4, 5-diphenyl-1H-imidazole-1-yl]-1H-indoles of Biological Interest

Microwave-assisted Solvent-free Synthesis of Some New 4-[2-(Substituted phenyl)-4, 5-diphenyl-1H-imidazole-1-yl]-1H-indoles of Biological Interest

Montmorillonite clay modified by CuFe2O4 nanoparticles, an efficient heterogeneous catalyst for the solvent-free microwave-assisted synthesis of 1,3-thiazolidin-4-ones

Montmorillonite clay modified by CuFe2O4 nanoparticles, an efficient heterogeneous catalyst for the solvent-free microwave-assisted synthesis of 1,3-thiazolidin-4-ones

Microwave-assisted solvent-free synthesis, Hirshfeld surface analysis and DFT studies of 1-(hydroxymethyl)-pyrazoles

A facile high-yield, solvent-free approach for the synthesis of a series of 1-(hydroxymethyl)-pyrazoles under microwave irradiation was developed for the first time. The structures of four pyrazoles compounds were characterised by a single-crystal X-ray diffraction, and showed interesting intermolecular O‒H∙∙∙N hydrogen bonding linking two pyrazoles molecules to form R22(10) dimer architectures. In additional, the intermolecular interactions in the crystal were investigated through the Hirshfeld surface analysis to understand the characteristics of the close contacts, and the 2D-fingerprint plot data exposed that a significant contributions to the crystal packing are from N∙∙∙H/H∙∙∙N contacts. The geometry optimization, electronic properties and energies level of HOMO, LUMO were performed by Density functional theory (DFT) calculations. Quantitative electrostatic potential analysis (ESP) and independent gradient model based on Hirshfeld partition (IGMH) explained the active hydrogen bonding sites in four pyrazoles compounds and confirmed the hydrogen bonding modes in their crystal structure.

Microwave-assisted solvent-free synthesis of some novel thiazole substituted thiosemicarbazone analogues: Antimicrobial and anticancer studies.

The increased resistance to antibiotics has compelled researchers to devise novel active compounds targeting multidrug-resistant pathogenic microorganisms. A series of thiosemicarbazone derivatives were synthesized by reacting thiosemicarbazide with 2-aryl-4-formylthiazole, 2-aryl-5-formyl-4-methylthiazole, and/or 5-acetyl-2-aryl-4-methylthiazole compounds. These thiosemicarbazone-based thiazole adducts were evaluated for their inhibitory activities against tuberculosis H37Ra and Bovis BCG mycobacteria. Their cytotoxicity was assessed against two cancer cell lines: colonic carcinoma (HCT-116) and cervical cancer (HeLa). Notably, these thiosemicarbazones exhibited minimal cytotoxic effects on these cell lines even at their highest concentrations. Furthermore, the prepared thiosemicarbazone derivatives demonstrated significant antimicrobial efficacy against Bacillus subtilis and Staphylococcus aureus (gram-positive bacterial pathogens) as well as Escherichia coli and Pseudomonas fluorescens (gram-negative bacterial pathogens). While most of the prepared thiosemicarbazone derivatives exhibited moderate activity against Candida albicans (a fungal strain), their performance was notable. The thiosemicarbazone-based thiazole adducts were also successfully synthesized using a solvent-free approach under microwave irradiation. Compared with conventional reflux methods, the microwave-assisted technique yielded high thiazole yields within just 5 minutes, obviating the need for catalysis. This study signifies significant strides toward the rational design of more potent antimycobacterial agents.

Solvent-free Microwave-assisted Synthesis of 1-(1,3-diphenyl-1H-pyrazol- 4-yl)-3-(2-hydroxyphenyl) Propane-1,3-dione Using K2CO3 as Green Solid Support

Abstract:: We herein present the synthesis of 1-(1,3-diphenyl-1H-pyrazol-4-yl)-3-(2-hydroxysubstituted phenyl) propane-1,3-dione using microwave irradiation. Reactions were carried out by employing a solvent-free path using K2CO3 as green solid support. The results were compared with those of the conventional method. This microwave-assisted synthesis avoids hazardous solvents and reduces the number of steps and time, providing increased yields. The synthesized products were characterized by IR, 1H NMR, and mass spectrometry.

Tetraiodophthalocyanines: Simple and convenient synthetic protocol and structural modification via Sonogashira cross-coupling reaction

Planar and sandwich-type iodo-substituted phthalocyanines – precursors for cross-coupling reactions were synthesized starting from 4-iodophthalonitrile via a novel user-friendly synthetic strategy. For this purpose, 4-iodophthalonitrile was prepared following the multi-step protocol, including nonclassical version of diazotization/iodination reaction in the presence of p-toluenesulfonic acid. Tetraiodophthalocyaninato Zinc(II) was obtained using a solvent-free microwave-assisted synthesis. For the first time, the polyphosphoric acid was applied to the demetallation of halogen-substituted phthalocyanine complex. Under these conditions, demetallation of Zinc(II) complex occurred in a good yield without the oxidation of peripheral iodogroups. The Sonogashira cross-coupling reaction between the 2(3),9(10),16(17),23(24)-tetraiodophthalocyanine and model (trimethylsilyl)acetylene resulted in a target compound in a high yield (94%). The versatility of iodo-substituted phthalocyanine precursors was demonstrated on the examples of the synthesis of novel tetra-(3-hydroxyprop-1-yn-1-yl)- phthalocyaninato Zinc (II) (52% yield), bis[tetra(2-trimethyhilyethynyl)phthalocyaninato] Lutetium (III) (45% yield). Target compounds were identified by nuclear magnetic resonance, infrared spectroscopy, and mass spectrometry. UV–Vis properties of target compounds were investigated and compared with literature data. The key compounds were characterized by elemental analysis.

A Simple and Convenient Synthesis of 2, 3-dihydroquinazolin-4(1H)-one Derivatives using MgFe2O4@SiO2-SO3H Catalyst

In the present study, use of MgFe2O4@SiO2-SO3H as an efficient, green, magnetically recoverable & recyclable catalyst for micro-wave assisted solvent free synthesis of 2,3-dihydroquinazolin-4(1H)-ones reaction pathway is presented. The superiorities of this method are higher conversion rate, shorter reaction time, easy isolation of product and reusability of catalyst without remarkable loss of activity. The synthesized 2,3-dihydroquinazolin-4(1H)-ones derivatives were assessed for their antimicrobial and antifungal activity; where, the most of these compounds exhibit potent antibacterial and antifungal activities against various bacteria and fungi.

Microwave-assisted synthesis, biological assessment, and molecular modeling of aza-heterocycles: Potential inhibitory capacity of cholinergic enzymes to Alzheimer's disease

A highly regioselective solvent-free microwave-assisted synthesis of pyrazoles and tetrahydroindazoles based on the condensation of 1,3-diketones with arylhydrazines is described. Compounds were evaluated as cholinesterase inhibitors in order to identify an alternative treatment for Alzheimer's disease. All compounds displayed moderated acetylcholinesterase inhibitory activity and most of the compounds displayed remarkable butyrylcholinesterase inhibitory activity and selectivity. The compounds 3y and 3i with IC50 of 1.65 and 3.59 µM, respectively, were the most active and selective compounds as butyrylcholinesterase inhibitors. Likewise, the compounds were tested as antioxidants agents, results showed that they have the ability to trap free-radicals. Molecular Docking studies showed a key π-π stacking interaction of most of the compounds with residue Trp82 within of butyrylcholinesterase active site. Molecular quantum similarity field, global and local reactivity descriptors, and the Fukui functions were calculated in the Density Functional Theory framework to analyze the reactivity patterns along with the molecular set.

Microwave-Assisted Solvent-Free Rapid Synthesis of 4-Methyl Coumarin Derivatives by Using Silica functionalized-SO3H as an Effective Heterogeneous Catalyst

A novel silica gel functionalized-SO3H as a heterogeneous catalyst was prepared and characterized by FT-IR, XRD, TGA and elemental analysis. It has been studied for microwave-assisted solvent-free Pechmann condensation. The result revealed that 20% w/w silica bonded 3-mercapto propyl diethylene diamine N-sulfamic acid (SMPDDSA) was found to be effective. 4-methyl coumarin derivatives were the only product obtained in good to excellent yield (75–94%). The present protocol accomplishes the reaction in much lesser time as compared to the conventional method.

Solvent-free microwave-assisted synthesis of imidazo[1,5- a]pyridine and –quinoline derivatives

A quick and highly efficient microwave-assisted preparation of imidazopyridines and –quinolines is described, starting from the corresponding ketones and amines. The method requires no solvent and uses activated MnO2 as an oxidant. A mechanism for the cyclization is proposed and discussed.

An Efficient Solvent-Free Microwave-Assisted Synthesis of Cinnamamides by Amidation Reaction Using Phenylboronic Acid/Lewis Base Co-catalytic System

A microwave-assisted dehydrative amide condensation reaction is reported as an efficient access to cinnamamide derivatives under solvent-free conditions. This protocol between conjugated carboxylic acids and amines is based on the use of a co-catalytic system, including the presence of the commercially available phenylboronic acid and 4-(N,N-dimethylamino)pyridine N-oxide (DMAPO), with a complete chemoselectivity in favor of the corresponding α,β-unsaturated amides. The implementation of the reaction needs no special precaution, and less reactive amines, such as substituted anilines, are also efficient under these conditions. A series of novel conjugated amides have been evaluated for their cytotoxic activities against several human cancer cell lines.

A Facile and Microwave Assisted Solvent Free Synthesis of Novel Indole Pyrimidine Imide Derivatives

A series of novel indole derivatives bearing pyrimidine and cyclic imide scaffolds such as phthalic and maleic anhydrides has been designed and synthesized using both conventional and microwave irradiation (MW) methods under solvent free conditions. The title compounds have been developed by the reaction of 2-aminoo-4-hydroxy-6-(5,1-substituted-indol-3-yl) pyrimidine-5-carbonitrile with phthalic and maleic anhydrides individually using MW method. In addition, these target compounds were also synthesised under conventional heating method. A considerable increase in the reaction rate has been observed with better yields (90–92%) within 2–6 min using microwave irradiation in comparison to conventional thermal treatment.

Creation of DABCO‐Based Amphoteric Ionic Liquid Supported TiO2 Nanoparticles: Execution of Amplified Catalytic Properties on Microwave‐Assisted Synthesis of N‐Substituted Pyrroles

AbstractThis is the first report of DABCO based amphoteric ionic liquid supported TiO2 nanoparticles, a supported catalyst with an ionic liquid layer (SCILL). It is highly efficient, recyclable, quasi heterogeneous catalyst for microwave assisted solvent free synthesis. Highly polar DABCO based ionic liquid with high dielectric constant of titanium dioxide nanoparticles enables the system as efficient microwave irradiation absorber. Amplified catalytic properties of this new combined green catalytic system have been first time implemented for the chromatography‐free synthesis of highly functionalised pyrrole moieties under microwave assisted solvent‐free conditions. The generation of catalyst and ionic liquid capping over titanium dioxide nanoparticles were characterised via Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Thermo Gravimetric Analysis (TGA), Dynamic Light Scattering (DLS), Powder X‐Ray Diffraction (PXRD), Energy Dispersive Analysis X‐ray (EDAX) and Fourier Transform Infrared Spectroscopy (FT‐IR spectra). This combined quasi heterogeneous twin catalytic system, containing both acidic and basic environment afford the desired products in excellent yields within short reaction time. Here, the catalytic effect featuring the synergetic effect of titanium dioxide nanoparticles and amphoteric DABCO based ionic liquid were magnificently tethered.

Solvent-free microwave-assisted synthesis and characterization of polybenzoxazine as a thermochromic material for smart coatings

An alternative to conventional synthesis route, here we have developed a novel thermochromic material based on phenolic resin via solvent-free microwave-assisted synthesis. In this work, we have prepared bisphenol-A-based polybenzoxazine with the potential to be used as an irreversible thermochromic material. The material may be used individually or as a part of smart coatings. The polymerization was further confirmed by Fourier-transform infrared spectroscopy (FTIR) which gives confirmation that the synthesized material is polybenzoxazine by the means of characteristic peaks.

Ecofriendly microwave assisted synthesis of some new pyridine glycosides

An efficient, mild and rapid procedure was employed to prepare a novel series of pyridine glycosides. The protocol allows the reaction of 2-pyridone with 1,2,3,4,6-penta-O-acetyl-α-D-glucopyranose under solvent-free microwave-assisted synthesis using different solid supports. Silica gel has been found to be an efficient and environmentally friendly promoter. Structures of the new products were confirmed based on their elemental analyses and spectral data (LC-MS/MS, IR, UV, 1D- and 2D-NMR).

Solvent-free microwave-assisted synthesis of tenorite nanoparticle-decorated multi-walled carbon nanotubes

Copper-decorated carbon nanotubes (CNTs) have important applications as precursors for ultra-conductive copper wires. Tenorite-decorated CNTs (CuO-CNTs) are ideal candidates and are currently developed using laborious processes. For this reason, we have developed a facile and scalable method for the synthesis of CuO-CNTs from copper acetate. It was found that the optimal loading of copper acetate onto the CNTs was 23.1 wt% and that three 1-minute microwave treatments were sufficient for the decomposition of copper acetate to copper oxide. The loading of copper oxide onto the nanotubes was confirmed using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. The materials were characterised using X-ray diffraction and scanning electron microscopy.

Synthesis, Crystal Structure, and Studies on Mechanism of D-π-A Ferrocene Derivative

Microwave-assisted solvent-free synthesis of new (D-π-A) chromogenes, 2-ferrocenyl-1,1-dicyanobuta-1,3-diene derivatives (II), have been accomplished through the condensation of 2-(1-ferrocenylethylidene)malononitrile (I) and aromatic aldehydes with sarcosine as the catalyst and identified by 1H NMR, 13C NMR and FT-IR. Compound IId was determined by X-ray crystallography (CIF file CCDC no. 1056735). The crystal belongs to monoclinic, space group P21/c. The possible reaction mechanism has been studied.

Microwave-assisted solvent-free synthesis and spectral and structural characterization of cyclotriphosphazene hexakis(o-tolylamide)

AbstractA new cyclotriphosphazene, 2,2,4,4,6,6-hexakis (o-tolylamono)-1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine (MPAP), was prepared using microwave irradiation and identified by elemental analysis, FT-IR, Raman,31P NMR spectroscopy, and single-crystal X-ray diffraction. In the crystal, in addition to hydrogen bonds, the network is further stabilized by inter- and intramolecular π–π stacking interactions between aromatic rings.

Microwave-promoted solvent free one-pot synthesis of triazolo[1,2-a] indazole-triones catalyzed by silica-supported La0.5Ca 0.5CrO3 nanoparticles as a new and reusable perovskite-type oxide

Microwave assisted solvent free synthesis of triazolo[1,2-a]indazole-1,3,8-triones through one-pot three-component reaction of dimedone, phenyl urazole and aromatic aldehydes is presented. The reaction process was catalyzed by La0.5Ca0.5CrO3 and silica-supported La0.5Ca0.5CrO3 nanoparticles as new perovskite-type catalysts. The nano catalyst was studied by XRD, SEM and IR characterization tools. Some advantages of the proposed approach include high yield, being eco-friendly, procedure convenience and reusability of the catalyst. KEY WORDS: One-pot reaction, Triazolo[1,2-a]indazole trione, Perovskite oxide, Nano catalyst, Microwave, Solvent-free Bull. Chem. Soc. Ethiop. 2018, 32(2), 239-248.DOI: https://dx.doi.org/10.4314/bcse.v32i2.5