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Aims: Synthesis of dihydropyrimidinones derivatives. Background: carrying out reactions in the green route and organic solvent-free conditions. Objective: Regioselective Michael addition of dihydropyrimidinones to acrylic esters. Methods: The reaction proceeded in the presence of K2CO3/TBAB, a media of inorganic base K2CO3 and organic ionic salt TBAB (tetrabutylammonium bromide) at 100oC. Results: A series of new dihydropyrimidinone derivatives using aza-Michael addition reaction were synthesized under solvent-free conditions. Conclusion: The reaction is characterized by high efficiency, relatively short reaction time, high yields, simple environmentally friendly reaction conditions. Other: The reaction of acrylic esters with dihydropyrimidinones produced N3-substituted derivative of dihydropyrimidinones with 85-95% yields in 6 h.

In this work, new pyrazole derivatives were prepared by one-pot three-component reaction emloying symmetric and asymmetric 1,2-disulfonyl-hydrazines, cyclohexyl isocyanide, and dialkyl acetylenedicarboxylates. Reactions with asymmetric 1,2-disulfonylhydrazines led to two regioisomers, which were distinguished by density functional theory calculations and the major isomer attributed to the energically more stable one.

Laccase/DDQ as a new bioinspired quinone-based cooperative catalytic system was used for the biomimetic aerobic oxidative synthesis of 2-substituted quinazolines and Hantzsch pyridines from the oxidative cyclocondensation of 2-aminobenzylamine and aldehydes and the oxidative aromatization of 1,4-dihydropyridines, respectively. The products were obtained in good to high yields in a phosphate buffer (0.1 M, 12.5 mL, pH 4.5) and acetonitrile (4 vol%) mixture as a solvent. These methods are more eco-friendly, efficient, simple, and practical than other currently available ones because of mild reaction conditions and because they are free from any halide and toxic and expensive transition metals. Therefore, these methods can be applied in pharmaceutical and other sensitive synthetic procedures.

In this research paper, for the first time laccase from Trametes Versicolor was used as a electron-transfer biocatalyst for the aerobic regeneration of DDQ as a high reduction potential organic oxidant. Laccase/DDQ as a new bioinspired quinone-based cooperative catalytic system was used for the aerobic oxidation of sulfides and oxidative coupling of thiols with high yields at room temperature. The herein presented method is more eco-friendly and practical than other currently available methods as it is free from any toxic transition metals or halides and provides quantitative conversion under mild reaction conditions.

A manipulative simple and efficient green methodology for the synthesis of β-sulfonyl esters from sulfonyl hydrazides and acrylic esters promoted by DABCO (1,4-diazabicyclo[2.2.2]octane) is described. The reaction is conducted through sulfa-Michael addition reaction in the absence of solvent at 75°C within 2–3 h. The effects of different bases, molar ratio of DABCO, temperature and time parameters on yield of reaction were investigated.

In the present paper, silver nanoparticles (AgNPs) were synthesized using the Brassica oleraceae fruit extract under the simple and eco-friendly conditions. The reaction between silver nitrate, as metal source, and aqueous extract of Brassica oleraceae fruit, as reductant agent, produced AgNPs in high yield. The formation of AgNPs was confirmed by means of UV-Vis spectroscopy and scanning electron microscopy (SEM) was used for characterization of morphology and size of silver nanoparticle products. The investigation of diverse reaction parameters revealed that reductant concentrations, reaction pH, mixing ratio of the reactants and interaction time affected the size and morphology of synthesized AgNPs. AgNPs with 32.74 nm size and amorphous, based on SEM images, were produced within 24 h interaction period. AgNPs also showed a good antibacterial activity against Escherichia coli.

A new series of pyrrolo[3,4-b]quinolin-2(3H)-yl)benzamides were designed based on molecular hybridization approach and synthesized by reaction of benzohydrazide derivatives with 9-phenylfuro[3,4-b]quinoline-1,3-diones in the presence of an Et3N catalyst. Simple reaction, excellent yield, simple separation process and eco-friendly approach by minimizing the chemical waste renders this protocol particularly attractive. The series 9a–g was evaluated for in vitro antibacterial activity against (+ve bacteria) Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212, (−ve bacterium) Escherichia coli ATCC 25922. In vitro minimum inhibitory concentration (MIC) evaluations showed that the compound 9a was effective against E. coli (MIC: 0.25 mg/mL) S. aureus (MIC: 0.25 mg/mL) and E. faecalis (MIC: 0.5 mg/mL).

In this paper, we offered a green, environment-friendly, novel and inexpensive method for the synthesis of a series of pyrazole derivatives. The reaction took place in the presence of tetrabutylammonium bromide, a commercially available organic ionic salt, at room temperature under solvent-free conditions. All products were confirmed by infrared radiation, nuclear magnetic resonance and elemental analysis. Yields of products were 75–86%.

In this paper, C–N bond formation between 2,3-dihydrophthalazine-1(4H),4-dione (phthalhydrazide) and α,β-unsaturated esters was investigated and a new series of phthalazine derivatives was synthesized using an efficient and simple method under solvent-free conditions. An aza-Michael addition of phthalhydrazide to both acrylic and fumaric esters led to N-mono-substituted phthalhydrazides (as mono-Michael adduct) in the presence of tetrabutylammonium bromide as a high polar media, and 1,4-diaza-bicyclo[2,2,2]octane as an available organic base. In this reaction, the N1,N2-bis-Michael adduct was not observed at all. Also, reactions were performed at 90°C and yields of products were good to excellent.

A simple, efficient and clean procedure has been developed for the cleavage of imines C=N bond. Deprotection of imines to their parent carbonyl and amine compounds was achieved using p-toluenesulfonic acid in the solid state condition at 25-45 ˚C. The salient features of this methodology are shorter reaction times, cheap processing, high yields of product and easy availability of the catalyst. These features make this method an attractive alternative to existing routes for deprotection of iminesA simple, efficient and clean procedure has been developed for the cleavage of imines C=N bond. Deprotection of imines to their parent carbonyl and amine compounds was achieved using p-toluenesulfonic acid in the solid state condition at 25-45 ˚C. The salient features of this methodology are shorter reaction times, cheap processing, high yields of product and easy availability of the catalyst. These features make this method an attractive alternative to existing routes for deprotection of imines

A new series of spiro[[1,3]dithiolane-2,3′-indolines]-2′-one derivatives was synthesized using Michael addition reaction of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one to various α,β-unsaturated esters as well as direct alkylation of this compound with alkyl dihalides. Michael reaction of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one and α,β-unsaturated esters produced related Michael adduct in the presence of tetrabutylammonium bromide and base 1,4-diazabicyclo[2.2.2]octane in good to excellent yields at 80°C under solvent-free conditions. Also, direct alkylation of spiro[[1,3]dithiolane-2,3′-indolin]-2′-one by dihaloalkanes in the presence of base K2CO3 afforded the corresponding products in good yields under the same conditions.

An unexpected reaction between 4-phenylurazole and fumaric esters which led to the formation of 5-alkylidene derivatives of hydantoin is described in this paper. The reaction takes place in the presence of tetrabutylammonium bromide (TBAB), and 1,4-diaza-bicyclo[2,2,2]octane (DABCO) at 70 °C under solvent-free conditions.

The adsorption behavior of H2S gas on the P‒doped, V/P, Nb/P, and Ta/P‒codoped g-C3N4 were theoretically investigated using density functional theory. The computed adsorption energy of H2S molecules over the P‒doped, V‒embedded, Nb‒embedded, Ta‒embedded, V/P‒codoped, Nb/P‒codoped, and Ta/P‒codoped g-C3N4 systems are −0.188, −3.141, −2.850, −3.388, −3.263, −2.970, and −3.523 eV, respectively. These results revealed that with embedding and codoping of g-C3N4, the interaction energy between H2S and V/P, Nb/P, Ta/P‒modified g-C3N4 systems significantly enhances. Furthermore, the band structure results exhibited that with adsorption of H2S on g-C3N4 and also embedded and codoped systems, the electrical conductivity of the g-C3N4 systems remarkably decreases owing to the induced new impurity energy states near the Fermi energy level. Also, the results of the relaxed structures displayed that with adsorption of H2S molecules on g-C3N4 and also the modified g-C3N4 with V, Nb, and Ta and also P elements, the initial planar structure of the pristine g-C3N4 automatically become buckle because the stability of wrinkles structure of g-C3N4 is more than that of the flat structure. Additionally, the results of the Lowdin charge analysis revealed that electron transfer occurs from orbitals of transition metals to the orbitals of H2S molecules for all of the g-C3N4 systems. Finally, current research introduces Ta/P‒codoped g-C3N4 system with adsorption energy of −3.523 eV as the highest sensitive, and low-cost gas sensor candidate for sensing and removing H2S gas from the atmosphere.

A quantum mechanical density functional theory (DFT) was successfully developed for the estimation of pKa values of chlorinated phenols in aqueous solution with a precision of 0.9 pKa units. The MP2/6-311++G(d,p)//B3LYP/6-31+G(d) level of theory was used for the gas phase calculation. For computation in the solution phase and to calculate the energy difference of the acid-base, the polarized continuum model (PCM) at the HF/6-31G(d,p) level was used. The pKa value was computed for each involved species using pentachlorophenol (PCP) as a reference molecule. Natural bond orbital (NBO) analysis considering the natural resonance theory (NRT) was carried out on an optimized geometry of studied compounds to give information about the nature of bonds. Graphical abstract Chlorinated phenols.

The highly regioselective C-N bond formation between phenytoin and acrylic/fumaric esters was accomplished. Solvent-free media Michael addition of phenytoin to acrylic esters led to the selective synthesis of N3-substituted phenytoins (as mono-Michael adducts) in the presence of tetrabutylammonium bromide (TBAB) and potassium carbonate under ultrasonic irradiation conditions at room temperature. These reactions produced N1,N3-disubstituted phenytoins (as bis-Michael adducts) at 70 oC. Surprisingly, the addition of phenytoin to fumaric esters, instead of acrylic esters, selectively provided only N3-substituted phenytoins at both room temperature and 70 oC under the same conditions.

The direct polycondensation of a monomer derived from l-aspartic acid together with adipic acid as a modifier co-monomer with aromatic diamines was studied to synthesize co-poly(amide-imide)s (CPAIs). The relative reactivity of the co-monomers and the manner of their insertion into polymer chains were evaluated using a model reaction and 1H NMR spectroscopy, respectively. The synthesized polymers depicted optical rotations similar to those of the monomer precursor and inherent viscosities in the range of 0.13–0.95 dl/g. Thermal stability and behavior as well as the weight-loss pattern of the CPAIs were studied by thermo-analytical techniques (thermogravimetric analysis-differential thermal analysis, dynamic mechanical thermal analysis and differential scanning calorimetry). Onset decomposition temperatures >300°C and carbonization residues of more than 50% at 600°C were detected for the treated polymers. Almost all of the copolyamides were noncrystalline solids, as illustrated in the X-ray diffraction patterns, and had good levels of solubility in a variety of polar organic solvents. These polymers could afford transparent and flexible to brittle films in solution casting on glass plates. Scanning electron microscopy on the polymer films showed a uniform and continuous morphology, indicating good film forming ability.

Trisubstituted quinolines and acylhydrazones were unexpectedly prepared from a reaction of N′-((2-aminophenyl)(phenyl)methylene)benzohydrazides with acetylenic esters. Using of N′-((2-aminophenyl)(phenyl)methylene)benzohydrazides led to obtain not only quinoline, but also a second pharmaceutical important product acylhydrazone. Notably, excellent yields, operational simplicity, short reaction times, and the avoidance of the use of catalysts make this approach an attractive complementary method to produce quinoline-2,3-dicarboxylates. The crystal structure of 5a was determined using single-crystal X-ray crystallography. The results showed that crystal packing diagram of 5a is of two pairs of molecules that have two independent alternate intermolecular 1D-polymeric H-bonds between two perpendicular molecules.

The reaction of 4-phenylurazole and fumaric esters in the presence of tetrabutylammonium bromide results in the formation of 5-alkylidene derivatives of hydantoin under solvent-free conditions.

A regioselective N3-alkylation of 5,5-diphenyl-2-thiohydantoin (2-thiophenytoin) using a very efficient mild base K2CO3 and α,β-unsaturated esters in the presence of organic salt TBAB (tetrabutylammonium bromide) at room temperature has been reported (3b–3h). The selectivity of this reaction is excellent and products have been produced in good yields under solvent-free conditions. The increase of the reaction temperature to 70°C mostly disappeared this selectivity and afforded only the N1,N3-dialkylated derivatives of 2-thiophenytoin in good yields (4b–4g). We were unable to selectively N3-alkylate 2-thiophenytoin with ethyl acrylate at both room temperature and 70°C under the same conditions (4a). Dimethyl and diethyl fumarates cannot work as Michael acceptors and were hydrolyzed to fumaric acid under reaction conditions.