SnO2 nanoparticles: A recyclable and heterogeneous catalyst for Pechmann condensation of coumarins and Knoevenagel condensation-Michael addition of biscoumarins.

Recyclable SnO2 nanoparticles catalyze the Pechmann condensation between phenolic alcohols and ß-ketoesters at room temperature in ethanol leading to coumarins. Also, in another study the synthesis of biscoumarins catalyzed by SnO2 nanoparticles in the reaction between 4-hydroxycoumarin and aldehydes under same condition reactions. The corresponding coumarins and biscoumarins were produced efficiently with facility and excellent yields (93-98%). These approaches display the advantages of benign reaction conditions, non-chromatographic purification procedure, appropriate functional group tolerance and valuable process.

Retraction: Design of 1-methylimidazolium tricyanomethanide as the first nanostructured molten salt and its catalytic application in the condensation reaction of various aromatic aldehydes, amides and ß-naphthol compared with tin dioxide nanoparticles.

[This retracts the article DOI: 10.1039/C5RA02718G.].

Advancements in Fabrication and Application of Chitosan Composites in Implants and Dentistry: A Review.

Chitosan is a biopolymer that is found in nature and is produced from chitin deacetylation. Chitosan has been studied thoroughly for multiple applications with an interdisciplinary approach. Antifungal antibacterial activities, mucoadhesion, non-toxicity, biodegradability, and biocompatibility are some of the unique characteristics of chitosan-based biomaterials. Moreover, chitosan is the only widely-used natural polysaccharide, and it is possible to chemically modify it for different applications and functions. In various fields, chitosan composite and compound manufacturing has acquired much interest in developing several promising products. Chitosan and its derivatives have gained attention universally in biomedical and pharmaceutical industries as a result of their desired characteristics. In the present mini-review, novel methods for preparing chitosan-containing materials for dental and implant engineering applications along with challenges and future perspectives are discussed.

Ag-TiO2 Nanoparticles-catalyzed Three-component Synthesis of 12-aryl- 8,9,10,12-tetrahydrobenzo[a]-Xanthen-11-ones in Aqueous Medium.

BACKGROUND: Ag-TiO2 nanoparticles catalyzed synthesis of 12-aryl-8,9,10,12- tetrahydrobenzo[a]-xanthen-11-ones have been enhanced via a three-component one-pot reaction betweenß-naphthol, several aldehydes and dimedone in H2O at room temperature. Xanthenes are essential intermediates in chemistry owing to their vast difference in biological activity. METHODS: This process offered significant advantages containing appropriate cost efficiency, low amount of the catalyst, application of low-cost available Ag-TiO2 nanoparticles catalyst, purification of the product by non-chromatographic method, easy process, good atom economy, simple isolation and reusability of nanocatalyst. RESULTS: Ag-TiO2 nanoparticles catalyst shows easy access to Xanthenes with appropriate yields in short reaction time and purity. This nanoparticles catalyst was recycled and recovered by easy filtration and was reused up to five times with only an unimportant loss in its catalytic efficacy. CONCLUSION: This method achieves to have a numerous scope relating to the difference in the aldehydes. Correspondingly, the attractiveness of this research was that H2O was the only by-product.

Synthesis of Fe3O4@chitosan@ZIF-8 towards removal of malachite green from aqueous solution: Theoretical and experimental studies.

Discharges of dyes-containing wastewater from industries have created global concern. Removal of these substances from aqueous solution is very important and essential. Magnetic chitosan coated with ZIF-8 was prepared successfully and used to eliminate cationic dye malachite green in various conditions. To find the effectiveness of ZIF-8 towards malachite green removal, their surface interaction was investigated using density functional theory (DFT) calculations for the first time which the results show physisorption of malachite green on ZIF-8. The characteristics of adsorbent synthesized were evaluated using XRD, FTIR, FE-SEM, TEM and TGA analysis. In addition, the influence of different parameters on malachite green removal was investigated. The results showed that pH = 7, 40 mg of adsorbent dosage, 10 mg/L initial concentration, 40 min contact time and temperature of 25 °C were obtained as an optimum values for Fe3O4@chitosan@ZIF-8. The equilibrium data were in good agreement with the Langmuir model having maximum capacity (qm) value of 3.282 mg/g. The experimental data revealed that the adsorption process obeyed to pseudo-second order kinetic model. It was concluded that Fe3O4@chitosan@ZIF-8 can be utilized as an efficient and effective adsorbent for removal of toxic malachite green dye from aqueous solution.

Cu(II) Schiff base complex as a highly efficient catalyst for the synthesis of polyhydroquinoline derivatives via Hantzsch condensation in water.

In the present study, Cu(II) Schiff-base complex is introduced as a highly efficient and green solid catalyst for the unsymmetrical Hantzsch condensation through a four-component coupling of various aldehydes, dimedone, ethyl acetoacetate and ammonium acetate to form polyhydroquinoline derivatives in good to excellent yields. This reaction was carried out in the presence of 1 mol% of catalysts in water at room temperature. The reusability of the catalysts was demonstrated by a five-run test. Remarkable features of this new procedure are cleaner reaction profiles, shorter reactiontimes, simple experimental and work-up procedures.

A green and efficient protocol for the synthesis of quinoxaline, benzoxazole and benzimidazole derivatives using heteropolyanion-based ionic liquids: as a recyclable solid catalyst.

In this paper, we introduce two nonconventional ionic liquid compounds which are composed of propane sulfonate functionalized organic cations and heteropolyanions as green solid acid catalysts for the highly efficient and green synthesis of 2,3-disubstitutedquinoxaline derivatives. These ionic liquids are in the solid state at room temperature and the synthesis is carried out via the one-pot condensation reaction of various o-phenylenediamine with 1,2-diketone derivatives. Benzoxazole and benzimidazole derivatives were also synthesized by these novel catalysts via the one-pot condensation from reaction orthoester with o-aminophenol (synthesis of benzoxazole derivatives) and ophenylenediamine (synthesis of benzimidazole derivatives). All experiments successfully resulted in the desired products. The described novel synthesis method has several advantages of safety, mild condition, high yields, short reaction times, simplicity and easy workup compared to the traditional method of synthesis.

Cu(II) Schiff base as catalyst in the synthesis of 1,8-dioxodecahydroacridine.

The catalytic property of Cu(II) Schiff-base complex in an efficient synthesis of 1,8-dioxodecahydroacridines was investigated. The one-pot three component reaction of dimedone, aromatic aldehydes and aromatic amines or ammonium acetate in water afforded the corresponding 1,8-dioxodecahydroacridines with excellent yields. This reaction was carried out in the presence of 1 mol% of catalysts at room temperature. The reusability of the catalysts was demonstrated by a five-run test without loss of its activity. Also, this catalyst possesses several advantages including mild reaction conditions, lower catalytic loading, shorter reaction times, high yield of the products, inexpensive and cleaner (Green chemistry) reactions.