Asian Journal of Green Chemistry
Volume:2 Issue: 2, Spring 2018

ZnFe2O4 as a novel nanoparticle was prepared and characterized using x-ray diffraction (XRD) analysis, energy dispersive x-ray (EDX), vibrating sample magnetometry (VSM), and fourier-transform infrared (FTIR) spectra. Then, it is used one-pot three-components synthesis of spirooxindole derivatives via condensation of isatin, malononitrile, and 1,3-dicarbonyl compounds (1,3-cyclohexanedione) under mild reaction conditions in water as a green solvent. The present methodology offers several advantages, including ease of the preparation and handling of the catalyst, simple and easy work-up, short reaction times, high yields of the products and recyclability of the catalyst.

A basic phase-transfer catalyst ([PEG(mim)2][OH]2) was prepared from the reaction of polyethylene glycol-bis(N-methylimidazolium) dibromide and sodium hydroxide dissolved in water at ambient temperature. The obtained white solid was used as an efficient basic phase-transfer catalyst in Knoevenagel condensation reactions between aromatic aldehydes and active methylene compounds in water at room temperature. The reaction is done without side products and in the presence of trace amounts of the catalyst gives the corresponding products with high yields. The phase-transfer catalyst could be successfully reused without significant decrease in its activity for at least five cycles.

Oxazole derivatives were prepared via multicomponent reaction of carbohydrazide, dialkyl acetylenedicarboxylate and ketone at room temperature under solvent-free conditions in good yields.  One of the alternative materials for this reaction is carbohydrazide. In this study, in addition to introducing the properties and applications of this material as an oxidizing agent, synthesis of this compound from hydrazine has been investigated. The production process consists of two steps in which the first step involves the reaction of dimethyl carbonate with hydrazine to produced methylhydrazinocarboxylate and methanol. In the second stage, hydrazine is first added to the produced intermediate and finally carbohydrazide is produced using crystallization, filtration and drying. The results of the prepared sample analysis indicate the production of high purity carbohydrazide.

The synthesis of benzo[f]chromeno[3,4-b]quinoline-6-ones has been achieved via one-pot three-component reaction from substituted aromatic aldehydes, 3-aminocoumarins, and 2-naphthol in n-butanol using 10 mol % of N-tetrabutylammonium tribromide (TBATB) as catalyst under reflux condition. The product formation is going through tandem Knoevenagel–Michael reaction followed by concomitant cyclization. The most noteworthy features of the present protocol are environmentally benevolent reaction conditions, simplicity of procedure, high atom economy, easy accessibility of the catalyst, cost effectiveness and superior yields. In addition, TBATB has also been found to be an effective catalyst for synthesising chromeno[3,4-b]quinoline-6,11-diones from substituted aromatic aldehydes, 3-aminocoumarins and cyclic 1,3-diketones with better yields in shorter reaction time.

Transition metals (ferrous ammonium sulphate and ammonium nickel sulphate) complexes have been proved to be efficient catalysts for transesterification of β-keto esters with various aromatic and hetero aromatic alcohols under solvent-free microwave conditions. However, in toluene media, the transesterification reaction was also conducted in both conventional reflux and sonication conditions, but, solvent-free condition microwave irradiation technique was found to be more efficient for transesterification with reduced reaction times and moderate yields. The inclination in reaction rates was found to be very less in solvent-free microwave assisted synthesis when compared to other conventional methods.

Aniline, phenol, and their derivatives are widely used in industrial chemicals that consequently have a high potential for environmental pollution. Genetic algorithm and partial least square (GA-PLS), kernel partial least square (GA-KPLS) and Levenberg-Marquardt artificial neural network (L-M ANN) techniques were used to investigate the correlation between chromatographic retention (log k) and descriptors for modelling the toxicity to fathead minnows of anilines and phenols. Descriptors of GA-PLS model were selected as inputs in L-M ANN model. The described model does not require experimental parameters and potentially provides useful prediction for log k of new compounds. Finally a model with a low prediction error and a good correlation coefficient was obtained by L-M ANN. The stability and prediction ability of L-M ANN model was validated using external test set techniques.

In this work, a simple and facile method for the preparation of tribromo melamine (TBM or melamine‐Br3) as an environmentally friendly homogeneous catalyst is described as it is used for the one-pot synthesis of benzimidazoles and benzoxazole derivatives via condensation reactions between aromatic aldehydes and ortho‐phenylenediamine or ortho‐aminophenol in aqueous media conditions. This green method offers significant advantages in terms of its simplicity, high catalytic efficiency, good to excellent product yields, use of ethanol as a green solvent, mild conditions, eco-friendly, and in acceptable reaction times.