Molybdate Sulfuric Acid/NaNO2: A Novel Heterogeneous System for the N‐Nitrosation of Secondary Amines under Mild Conditions

Wet molybdate sulfuric acid (= dioxo[bis(sulfato‐κO)]molybdenum; MSA), a new solid acid, can be used in combination with sodium nitrite (NaNO₂) to transform a variety of secondary amines to the corresponding N‐nitroso compounds under mild, heterogeneous conditions (Table). The process has several advantages: the reagents are inexpensive and non‐hazardous, the reaction is clean, fast, and high‐yielding, and MSA can be readily removed by filtration and re‐used (after treatment with HCl) without loss of activity. Further, only N‐nitrosation was observed, but no C‐ or O‐nitrosation.     

Antimicrobial activity of nanocellulose conjugated with allicin and lysozyme

In this study, cellulose nanoparticles were prepared by acid hydrolysis, separately conjugated with allicin and lysozyme by a carbodiimide cross-linker, and characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Then, their antimicrobial properties were evaluated by the microdilution method and compared with allicin, lysozyme, and nanocellulose alone. The results showed that nanocellulose had few antimicrobial activities, but allicin-conjugated nanocellulose (ACNC) and lysozyme-conjugated nanocellulose (LCNC) had good antifungal and antibacterial effects against standard strains of Candida albicans, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Noticeably, although allicin and lysozyme had different minimum inhibitory concentrations (MICs) against all strains, the same quantity of MIC₅₀ and MIC₉₀ was observed for both ACNC and LCNC. The authors suggest that both ACNC and LCNC can be used in industries as an antimicrobial agent in food packaging, inside foodstuffs, and in textile materials.     

Imidazol-1-yl-acetic acid as a novel green bifunctional organocatalyst for the synthesis of 1, 8-dioxooctahydroxanthenes under solvent-free conditions

Imidazol-1-yl-acetic acid is introduced as a new, efficient and recyclable green bifunctional organocatalyst for the synthesis of 1,8-dioxooctahydroxanthenes under solvent-free conditions. This catalyst is water soluble and can be separated from the products by simple filtration. The filtrate can be evaporated to dryness and recrystallized from cool methanol to give the recovered catalyst. This organocatalyst was used for the synthesis of 1,8-dioxooctahydroxanthenes under solvent-flee conditions and recycled up to 8 consecutive runs without any losing of its efficiency.     

An environmentally friendly synthesis of 1,4-dihydropyrano[2,3-c]pyrazole derivatives catalyzed by tungstate sulfuric acid

An efficient three-component synthesis of 6-amino-4-aryl-5-cyano-3-metriyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazoles via a reaction between 3-methyl-1-phenyl-2-pyrazolin-5-one,aromatic aldehydes and malononitrile using tungstate sulfuric acid as a catalyst was described.Mild conditions,good to excellent yields,easily available catalyst and easy work-up are the key features of this method.     

Green and Rapid Strategy for Synthesis of Novel and Known Pyrroles by the Use of Molybdate Sulfuric Acid

Molybdate sulfuric acid as a highly efficient catalyst has been employed for the modified Paal–Knorr synthesis of some novel and known pyrroles under solvent‐free conditions. Catalyst loads as low as 1 mol% could be used leading to high yields of pure pyrrole derivatives at an oil bath temperature of 60 °C. This method has advantages such as the use of very low amounts of a recyclable catalyst, avoidance of organic solvents, and high product yields.     

A Rapid Access to Novel and Known Benzimidazole Derivatives Using Silica Chloride as a Reusable Catalyst

A new application of silica chloride as an easily available and reusable solid acid catalyst for the synthesis of benzimidazole and its derivatives through the condensation of o‐phenylenediamines and orthoesters under thermal and solvent‐free conditions is described. This novel and eco‐friendly method is very cheap and has many advantages including excellent yields, short reaction time, and simple work‐up procedure.     

A one-pot,three-component synthesis of new pyrano[2,3-h]coumarin derivatives

The reaction between 5,7-dihydroxy-4-substituted coumarin, malononitrile, and aromatic aldehydes in the presence of a catalytic amount of K₂CO₃ as a basic catalyst leads to new pyrano[2,3-h]coumarin derivatives in good to excellent yields.     

A Modified Synthesis of Some Novel Polycyclic Aromatic Phenazines and Quinoxalines by Using the Tungstate Sulfuric Acid (TSA) as a Reusable Catalyst under Solvent‐free Conditions

Considering the synthesis of new compounds, we developed heterocyclic chemistry. We also helped to improve the classical synthetic route for the synthesis of quinoxalines and phenazines through implement in terms of solvent‐free reaction. For the condensation of 1,2‐dicarbonyls and o‐phenylenediamines under solvent‐free conditions at room temperature, tungstate sulfuric acid (TSA) was found to be an efficient and reusable reagent. The high yield of the pure products and simple preparation of the catalyst have allowed the synthesis of several phenazines and quinoxalines using this methodology.     

Regiospecific strategies for the synthesis of novel dihydropyrimidinones and pyrimidopyridazines catalyzed by molybdate sulfuric acid

The one-pot reactions of aryl glyoxals with acetylacetone and urea using molybdate sulfuric acid (5 mol %) lead to the novel functionalized 5-acetyl-4-(aryloyl)-3,4-dihydropyrimidinones, which readily undergo the Knorr condensation with hydrazines to produce new pyrimido[4,5-d]pyridazines. The present strategies are in accordance with green chemistry principles through the use of a safe and recyclable catalyst under solvent-free conditions.