Letters in Organic Chemistry - Volume 17, Issue 7, 2020

Friedel-Crafts reaction is one of the most useful synthetic tools in organic chemistry, mainly in the synthesis of aromatic ketones. The active catalysts for this reaction are modified zeolites and are preferable catalysts when shape selectivity affects the formation of the expected product. In this review, our aim is to corroborate recent literature available on zeolite catalyzed Friedel-Crafts alkylation and acylation reaction.

Sonochemical oxidative-coupling of formamides with 1,3-dicarbonyl compounds in the corresponding carbamates by CuO nanoparticles as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidant has been reported. Various derivatives of enol carbamates were synthesized with good to high yields under the optimized reaction conditions. Compared with conventional methods, the main advantage of this method is mild conditions.

Simple and clean access to pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidine derivatives using solvent- free and HSBM techniques through the multi-component reaction of 3-methyl-1-phenyl-1Hpyrazol- 5-amine, 1-aryl-2-thiocyanatoethan-1-one and aromatic aldehydes are reported. Using 2-hydroxyethan-1-aminium acetate as an ionic liquid, the product in high yields is obtained.

In the current study, a green, one-pot, three-component reaction was performed to prepare novel N-substituted 5-amino-1,3,4-thiadiazole derivatives. The thiadiazoles were obtained from the reaction of a ketene S,S-acetal of Meldrum’s acid or barbituric acid (as key intermediates), hydrazine, and isothiocyanate. The key advantages of this manner include environmentally safe reactions, high yield, appropriate reaction time, simple reaction conditions, and use of a green reaction solvent. The structure of thiadiazoles was determined based on the spectroscopic data.

In the present study, nickel nanoparticles (Ni-NPs) immobilized on graphene oxide-chitosan (GO-Chit-Ni) have been synthesized and characterized as a catalyst for reduction of nitroarenes in water. For this purpose, GO has been functionalized with chitosan (GO-Chit). Then, Ni-NPs were immobilized on the surface of GO-Chit using a simple method. The GO-Chi-Ni nanocomposites were characterized using Fourier Transforms Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), X-Ray Diffraction Measurements (XRD), and Atomic Adsorption Spectrometry (AAS). The GO-Chi-Ni nanoparticles demonstrated appropriate catalytic activity in reducing nitroarenes to aryl amines in the existence of sodium borohydride (NaBH4) aqueous solution as a hydrogen source at 80oC. This catalytic system applies environmentally benign water as a solvent that is cheap, easily accessible, non-toxic, non-volatile, non-flammable and thermally stable. This type of catalyst can be applied several times with no considerable change in its performance.

An efficient, simple and regioselective ring-opening reaction of epoxides with various carboxylic acids under metal-free conditions is reported. The ring-opening of epoxides takes place in the presence of graphite oxide as an efficient and available catalyst to produce the corresponding 2-hydroxy monoester and 1,2-diester derivatives in good yields. Regioselective attack of the nucleophile, short reaction times, metal-free conditions and reusability of catalyst are among the advantages of the present protocol.

A series of polybenzimidazole was synthesized by the solution polycondensation reaction of 3,3´-diaminobenzidine (DAB) with dicarboxylic acid derivatives. The synthesized polybenzimidazoles were characterized by using IR, 1H-NMR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA and DSC studies showed that the polybenzimidazoles have good thermal stability and are generally amorphous in nature. Glass transition temperature (Tg) values were found to be in the range of 300-410°C. This is the first detailed study to investigate the antimicrobial activities of the polybenzimidazoles. The synthesized polybenzimidazoles have high antimicrobial activity compared to benzimidazole molecules. It was also found that they are more effective against bacterial species than fungal species. The polymers 2, 5, 6, 7, having -1,3-phenyl, vinyl, -1-OH-3,5-phenyl and 4,4´- oxybisphenyl rings, showed remarkable activity against tested bacterial species (MIC = 32-500 μg/mL). Among these polymers, the polymers 6 and 7 having additional electronegative moiety have the highest activity against tested bacterial species.

A series of pyrazole-based heteroaromatic compounds were synthesized by the reaction of 3-methyl-5-pyrazolone and aromatic aldehydes in Choline chloride/urea DES as a green solvent. This simple and green procedure has advantages such as easy operation, short reaction times, efficient yields, low cost and minimum use of hazardous solvents and catalysts. The structure of compounds was determined by IR, 1H and 13C NMR spectra, and the crystal structure of 4a was confirmed using X-ray crystallographic analysis. The optical properties of Pyrazole derivatives 4a-g have also been studied with UV/vis and fluorescence spectroscopy. All of these pyrazole-containing heteroaromatic compounds displayed maximum emission peak from 340 to 360 nm.

Dioctyl sodium sulfosuccinate (DOSS) as a unique material both as a drug and surfactant was synthesized by a facile and economical synthetic method. In this project, Amberlyst-15 was selected as a heterogeneous recyclable bronsted solid acid for this synthesis both in the esterification of maleic anhydride and sulfonation of dioctyl maleate (DOM) ester. This catalyst was easily recovered and reused at least for 13 consecutive cycles without a significant loss in the catalytic activity. In this paper, we wish to uncover a catalytic approach for the synthesis of DOSS through a recyclable, easily recoverable, and commercially available catalyst, namely Amberlyst 15, under mild conditions.

The present work was aimed to synthesize eight new diphenylamine derivatives by the reactions of 2-chloro-N-(4-(diphenyl amino) thiazol-2-yl)acetamide with substituted phenols in the chloroform along with anhydrous potassium carbonate and potassium iodide. The structures of newly synthesized compounds were characterized by IR, NMR, Mass and elemental analysis techniques. Toxicity profile (acute and subacute oral toxicity) and biological activity (analgesic and anti-inflammatory activity) of the synthesized derivatives was performed. Findings of the present work suggested that the synthesized compounds may be one of the excellent potent compounds to treat pain and inflammation. Therefore compounds of this group especially AK-4 (N-(4-(diphenylamino)thiazol-2-yl)-2-(2- nitrophenoxy)acetamide) could be an excellent starting point to build up new lead compounds in the management of pain and inflammation.