Polystyrene sulfonic acid catalyzed greener synthesis of hydrazones in aqueous medium using microwaves

An environmentally benign aqueous protocol for the synthesis of cyclic, bi-cyclic, and heterocyclic hydrazones using polystyrene sulfonic acid (PSSA) as a catalyst has been developed; the simple reaction proceeds efficiently in water in the absence of any organic solvent under microwave irradiation and involves basic filtration as the product isolation step.     

Tandem bis-aza-Michael addition reaction of amines in aqueous medium promoted by polystyrenesulfonic acid

An efficient and environmentally benign tandem bis-aza-Michael addition of amines catalyzed by polystyrenesulfonic acid (PSSA) is described. This operationally simple high yielding microwave assisted synthetic protocol proceeded in water in the absence of any organic solvent.     

Synthesis of aryl-hydrazones via ultrasound irradiation in aqueous medium

The synthesis of aryl-hydrazones from aromatic aldehydes/ketones and hydrazides (semicarbazide, thiosemicarbazide and aminoguanidine) is described using aqueous medium (acid conditions) under ultrasound irradiation with short reaction times (20-30 min), the reactions occurring at room temperature and giving rise to good to excellent yields of the products, along with the diastereoselectivities. The procedure is also simple and clean.     

Green chemical multi-component one-pot synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones under solvent-free conditions and their anti-fungal activity

A rapid one-pot solvent-free procedure has been developed for the synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones by neat three-component cyclocondensation of anthranilic acid, phenyl acetyl chloride and substituted anilines under microwave irradiation. The experimental methodology and microwave conditions described here are well established, allowing significant rate enhancement and good yields compared to conventional reaction conditions. The reaction is generalized for O, M & P substituted anilines to give quinazolin-4(3H)-ones. Synthesized compounds have been screened for their antifungal activity.     

Green chemical multi-component one-pot synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones under solvent-free conditions and their anti-fungal activity

A rapid one-pot solvent-free procedure has been developed for the synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones by neat three-component cyclocondensation of anthranilic acid, phenyl acetyl chloride and substituted anilines under microwave irradiation. The experimental methodology and microwave conditions described here are well established, allowing significant rate enhancement and good yields compared to conventional reaction conditions. The reaction is generalized for o-, m- and p-substituted anilines with electron-donating and -withdrawing groups to give quinazolin-4(3H)-ones. Synthesized compounds have been screened for their anti-fungal activity.     

Synthesis of biologically important novel fluorinated spiro heterocycles under microwaves catalyzed by montmorillonite KSF

The arylidienes of fluorinated spiro thiazolidines (5) containing α,β-unsaturated function have been used as component of Micheal addition with equimolar amount of 2-aminopyridine (6a) to give novel fluorinated spiro [indole-3,2′-pyrido[1,2-a]thiazolo[5,4-e]pyrimidines] (7) in a single step under microwaves in presence of montmorillonite KSF as solid support. The new improved synthetic method for fluorinated spiro [indole-3,2′-thiazolo[4,5-d]pyrimidines] (8) has also been developed involving the reaction of (5) with thiourea under monomode microwave reactor. Comparison with conventional synthesis and multimode microwave oven indicated the enhanced yield with faster reactions under monomode microwave reactor. Structure-activity relationships between the chemical structures and the antimycobacterial, antifungal activity of the evaluated compounds are also discussed.     

Preparation and characterization of fluorinated acrylate copolymer latexes by miniemulsion polymerization under microwave irradiation

Fluoroacrylate copolymer miniemulsion was prepared by miniemulsion polymerization under microwave irradiation. The composition of the copolymer was determined by FTIR, DSC, ¹H NMR and ¹⁹F NMR. The morphology, size, and size distribution of the latex particles as well as changes in the size during polymerization were characterized by TEM and photon correlation spectroscopy (PCS). The effects of kinetic parameters on the polymerization were evaluated. The particle size of latex underwent almost no change during microwave irradiation polymerization. The diameters of latex particles prepared by microwave irradiation were smaller and more monodispersed than those prepared by conventional heating and the latex had good centrifugal stability. Polymerization under microwave irradiation had a higher reaction rate and higher conversion than traditional heating. By using 10 wt% fluoromonomer, the surface energy of the latex film could be reduced from 27.24 mJ/m² (latex film of fluorine-free) to 17.59 mJ/m² and the decomposition temperature increased by 25 °C.     

A simple and clean procedure for three-component synthesis of spirooxindoles in aqueous medium

A simple and efficient one-pot three-component synthesis of the biologically important spirooxindoles scaffold was carried out by the reaction of isatin, activated methylene reagent, and 1,3-dicarbonyl compounds in aqueous medium. This method is of great value because of its environmentally benign character, high yield processing, and easy handling.     

Comparison of various methods of grafting of modified-PEG onto maghemite nanoparticles in aqueous medium including synthesis by microwave refluxing

Three methods in the synthesis of functionalized maghemite nanoparticles in aqueous medium by grafting triethoxysilane monomethylene-PEG (Si-mPEG) onto maghemite nanoparticles were compared including synthesis by microwave refluxing which is an original device designed by our research team. The maghemite nanoparticles were characterized by zeta potential measurement, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The spinel structure of maghemite nanoparticles was determined and successful grafting of m-PEG was evidenced. Thermogravimetric analysis (TGA) reveals that microwave heating tends to improve the grafting rate compared to conventional heating.     

An efficient microwave-assisted Suzuki cross-coupling reaction of imidazo[1,2-a]pyridines in aqueous medium

A new simple, rapid and high yielding synthesis of various 6-aryl-2-arylsulfonylmethyl-3-nitroimidazo[1,2-a]pyridines by Suzuki cross-coupling reaction is described using microwave irradiation in aqueous medium without organic co-solvent in the presence of tetrabutylammonium bromide.     

Borax-catalyzed thiolysis of 1,2-epoxides in aqueous medium

A convenient, economical, and practical protocol for borax-catalyzed thiolysis of 1,2-epoxides in aqueous medium has been developed, which has greatly expanded the utility scope of borax in organic synthesis.     

Sodium chloride: a proficient additive for the synthesis of pyridine derivatives in aqueous medium

A facile and convenient synthesis of substituted pyridine derivatives catalysed by NaCl in the presence aqueous media under reflux and ultrasound irradiation has been developed via a one-pot multicomponent reaction, in which four new bonds were formed. Particularly valuable features of this protocol including mild conditions, simple execution, broad substrate scope and good yields of products make it an efficient and promising synthetic strategy to build pyridine skeleton.     

[Cp2TiCl2] as polymerization catalyst in aqueous medium: polymerization of styrene in water

The contrary to the general idea, an early transition metal organometallic compound, [Cp₂TiCl₂] has been found to be active catalyst for aqueous medium polymerization of styrene.     

Efficient extraction of PAHs in aqueous organised media assisted by focused microwaves

Summary A novel method for the extraction into an aqueous medium of PAHs in soil is described, where sodium dodecyl sulphate (SDS) is used as micelle former. After optimisation of this step using a multivariate approach, recoveries of the target analytes from spiked soil ranging between 98.3%–99.7% were obtained when the samples were subjected to extraction with 25 mL of an aqueous SDS solution (2.9 10⁻² mol L⁻¹) while irradiated with focused microwaves at 240 W for 40 min. The overall method involving determination of the extracted compounds consists of three steps: 1) extraction of the analytes into the aqueous micellar medium assisted by focused microwaves; 2) trapping of the analytes on a C₁₈ cartridge for clean up and preconcentration and; 3) HPLC separation with fluorimetric detection. The method was validated using the certified reference material CRM 524 and the results found were in agreement with the certified values.     

The synthesis of some 4-nitroisothiazoles as potential antifungal agents

5-Chloro-3-methyl-4-nitroisothiazole (III) was prepared by nitration of 5-chloro-3-methyliso-thiazole. Compound III was found to exhibit significant antifungal activity in vitro against a wide spectrum of fungi. The synthesis of 3-methyl-4-nitro-5-nitroamino, 5-carboxamido, 5-N,N-dimethylamino and 5-β-hydroxyethylaminoisothiazole are here reported. The synthesis of 3-methyl-4-nitroso-5-ethylthioisothiazole (IX) is reported via an unusual reaction of 5-bromo-3-methyl-4-nitroisothiazole (I) and sodium ethyl mercaptide. 5-Bromo-4-nitroisothiazole was prepared by nitration of 5-bromoisothiazole. The nitro group was shown to be essential for antifungal activity.     

Greener and rapid access to bio-active heterocycles: room temperature synthesis of pyrazoles and diazepines in aqueous medium

An expeditious room temperature synthesis of pyrazoles and diazepines by condensation of hydrazines/hydrazides and diamines with various 1,3-diketones is described. This greener protocol was catalyzed by polystyrene supported sulfonic acid (PSSA) and proceeded efficiently in water in the absence of any organic solvent within 1-2 min.     

Surface composition and property of film prepared with aqueous dispersion of polyurethaneurea-acrylate including fluorinated block copolymer

The aqueous dispersion of polyurethaneurea-acrylate (PUA) including small amount of fluorinated block copolymers containing carboxyl groups (PATF), which can be dissolved in water, was used to make films and the surface properties of these films were examined. The experimental data show that the modified PUA film exhibits a hydrophobic surface property, although the original surface of PUA film is hydrophilic. The surface composition of the modified PUA film was measured by ATR and XPS. The results indicate that there is a concentration gradient of the fluorine groups along the lines of thickness of the modified film and towards the outmost surface layer, resulting from the migration of fluorinated blocks to the air side surface of the modified PUA film during the film formation process. However, the PUA film can not be modified effectively by adding the sodium salt of PATF, since the urethane groups in the system are easy to occupy on the surface of the film.     

Thiamine hydrochloride as a promoter for the efficient and green synthesis of 12-aryl-8,9,10,12 tetrahydrobenzoxanthene-11-one derivatives in aqueous micellar medium

An environmentally benign, three-component, one-pot integrated chemical process has been developed for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzoxanthene-11-one by nucleophilic addition reaction between aldehyde and β-naphthol followed by Michael addition of dimedone, catalyzed by thiamine hydrochloride in aqueous micellar medium with excellent yield. Simple reaction conditions, no requirement of chromatographic separation, short reaction time, ease of isolation, use of inexpensive, easily recoverable and reusable catalyst makes this protocol very interesting from an economic and environmental perspective.     

An organocatalytic synthesis of N-sulfonyl imines using chloramine-T in aqueous medium

N-Sulfonyl imines have been synthesized in good to excellent yields from aldehydes and chloramine-T using proline as an organocatalyst in aqueous medium at ambient temperature. The protocol is applicable to a wide range of aldehydes, especially enals exhibit remarkable efficiency in the reaction. The reaction presumably occurs via iminium activation and opens new avenues for the synthesis of N-sulfonyl imines under environmentally benign and mild conditions.     

Resorcinarene supramolecular organocatalyst for functionalized 1-tetralone synthesis in aqueous medium

An efficient, straightforward and environmentally benign process has been developed for the synthesis of fluorenone and 1-tetralone derivatives using cyclic 1,3-dione, malononitrile and dialkylacetylenedicarboxylate as starting materials in aqueous medium. The reaction is favoured in presence of resorcin[4]arene which is effective as a reusable organocatalyst. The catalyst has been easily synthesized and characterized by ¹H, ¹³C NMR, IR, XRD and HRMS analyses. Resorcin[4]arene afforded the resulted products in a shorter time and in good yields. The recyclability of the catalyst was established up to 6th cycle by FT-IR and SEM images.