Zirconyl chloride: an efficient recyclable catalyst for synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 under solvent-free conditions

Zirconyl chloride was found to be an efficient catalyst for the cycloaddition reaction of aziridines with CO₂, thus leading to the preferential formation of 5-aryl-2-oxazolidinones under solvent-free conditions. The methodology could be extended to various substituted aziridines with high conversion and chemo-, regio-, and stereoselectivity. Furthermore, the catalyst could be reused over five times without significant loss in activity. Interestingly, the recovered catalyst showed higher activity in comparison with the fresh catalyst, presumably due to its morphological variation. The use of this cheap and moisture stable catalyst make this protocol practical, environmentally benign, and economically attractive.     

An efficient protocol for solid phase aminothiazole synthesis

An efficient synthesis of 2,4-diamino-5-ketothiazoles under solid phase conditions has been achieved by the reaction of polymer supported amidinothioureas with α-haloketones. This novel synthetic approach involving traceless cleavage from the support is suited for automation, and allows solid phase combinatorial synthesis of 2,4-diamino-5-ketothiazoles in good yields and purities.     

Solid phase extraction of petroleum carboxylic acids using a functionalized alumina as stationary phase

Petroleum essentially consists of a mixture of organic compounds, mainly containing carbon and hydrogen, and, in minor quantities, compounds with nitrogen, sulphur, and oxygen. Some of these compounds, such as naphthenic acids, can cause corrosion in pipes and equipment used in processing plants. Considering that the methods of separation or clean up the target compounds in low concentrations and in complex matrix use large amounts of solvents or stationary phases, is necessary to study new methodologies that consume smaller amounts of solvent and stationary phases to identify the acid components present in complex matrix, such as crude oil samples. The proposed study aimed to recover acid compounds using the solid phase extraction method, employing different types of commercial stationary ion exchange phases (SAX and NH(2)) and new phase alumina functionalized with 1,4-bis(n-propyl)diazoniabicyclo[2.2.2]octane chloride silsesquioxane (Dab-Al(2)O(3)), synthesized in this work. Carboxylic acids were used as standard mixture in the solid phase extraction for further calculation of recovery yield. Then, the real sample (petroleum) was fractionated into saturates, aromatics, resins, and asphaltenes, and the resin fraction of petroleum (B1) was eluted through stationary ion exchange phases. The stationary phase synthesized in this work showed an efficiency of ion exchange comparable to that of the commercial stationary phases.     

Wet cyanuric chloride promoted efficient synthesis of amidoalkyl naphthols under solvent-free conditions

An efficient and direct procedure has been developed for the preparation of amidoalkyl naphthols by a one-pot condensation of aryl aldehydes.2-naphthol and area or amides,in the presence of wet-cyanuric chloride(wet-TCT)as a catalyst.The reactions were carried out under solvent.flee media.The present methodology offers several advantages such as excellent yields,simple procedure and eco-friendly reaction condition.     

Synthesis of arylidenepyruvic amide derivatives via Ugi-four component condensation

Arylidenepyruvic acids (APAs) have been successfully employed in an Ugi-four component condensation reaction which yielded polyfunctional amides. Condensation of various APAs, aldehydes, amines, and isocyanides at room temperature in 96% ethanol as a green solvent proceeded in good yields. The extension of the reaction to diamines, formaldehyde, and isocyanides to form more complex molecules is also reported. These novel products may have potential in various pharmaceutical applications.     

Determination of triazines and amides in water using solid phase microextraction coupled with GC-MS

Summary Solid phase microextraction was coupled with gas chromatography-mass spectrometry (SPME-GC-MS) to screen for sixteen nitrogen-containing compounds, including herbicides, in water samples. The effects of stirring, extraction time, pH, salt concentration and the choice of fiber coating material were evaluated. The repeatability was in the range of 0.72–18.2 (CV % at 200 ng·L⁻¹) and the reproducibility, in the range of 5.4–34 (at 500 ng·L⁻¹).     

A traceless solid phase synthesis of thiomorpholin-3-ones

A novel synthesis of thiomorpholin-3-ones using a traceless solid phase approach is described, in which many kinds of thiomorpholin-3-ones were efficiently obtained in high purity based on an intramolecular alkylation of sulfides followed by an elimination of desired thiomorpholin-3-ones from the generated sulfonium salts.     

Aromatic homolytic substitution using solid phase synthesis

Solid phase synthesis has been used to carry out intramolecular aromatic homolytic substitution with benzoimidazole precursors. The protocol attaches the radical precursors to the resins via the radical leaving groups (in the aromatic homolytic substitution). When the radical reactions are complete, the leaving group, unaltered starting material and reduced uncylised products remain attached to the resin, which facilitates easy separation of the cyclised products. Novel use of focussed microwave irradiation in solid phase radical reactions drastically shortens the reactions times. Tributylgermanium hydride has been used to replace the toxic and troublesome tributyltin hydride in the radical reactions.     

Room temperature synthesis of benzimidazole derivatives using reusable cobalt hydroxide (II) and cobalt oxide (II) as efficient solid catalysts

Here we demonstrate the synthesis of benzimidazoles through the coupling of 1,2-phenylenediamine with aldehydes by using Co(OH)₂ and similarly CoO(II) as efficient solid catalysts in ethanol at room temperature. The Co(OH)₂ solid catalyst gave better yields (82-98%) in short reaction times (4-7 h) than CoO(II) catalyst (80-94%, 6-9 h). These commercially available cheap catalysts are more active than many reported expensive heterogeneous catalysts.     

Total synthesis of endothelin 1 by microwave-assisted solid phase method

<正>A microwave-assisted solid phase synthesis for endothelin 1 is presented.Reduced endothelin 1 was synthesized efficiently on Wang resin under microwave irradiation using Fmoc/tBu orthogonal protection strategy.The whole peptide was cleaved from the resin and two disulphide bridges were formed under air oxidation at room temperature.The purity and efficiency of synthesizing the peptide is much higher than other methods used before.     

Liquid and solid phase syntheses of orthogonally protected α-hydrazinoacid derivatives

The first solid phase synthesis of chiral α-hydrazinoacids has been developed. This synthesis was achieved by the preparation of solid supported-N-alkyloxycarbonyl-aminophthalimides used as acidic partners in the Mitsunobu protocol involving α-hydroxyesters. Two different final trans-protection steps of the phthaloyl group, developed first in liquid phase, result in efficient releases of orthogonally bis-protected or fully tris-protected hydrazine derivatives. A comparison between liquid and solid phase syntheses is outlined: even if the overall yields are sometimes rather higher by the liquid phase synthesis, the on-resin protocol is much more rapid and convenient than the liquid protocol.     

Repurposing n-butyl stannoic acid as highly efficient catalyst for direct amidation of carboxylic acids with amines

This is the first-time report on the repurposing n-butyl stannoic acid as a catalyst for direct amidation of carboxylic acids with amines. Notably, efficient amidation observed in comparison with all other catalytic methods reported up until now. The protocol has successfully applied to the synthesis of a variety of amides. Moderate reaction parameters, clean amidation with excellent yields of desired amides, ability to tolerate a variety of functional groups, easy product isolation; commercial availability and recyclability of the catalyst are key advantages of the current protocol.     

Highly efficient and green synthesis of 14-aryl(alkyl)-14H-dibenzo[a,j]xanthene and 1,8-dioxooctahydroxanthene derivatives catalyzed by reusable zirconyl triflate [ZrO(OTf)2]under solvent-free conditions

An efficient,convenient and green method has been introduced for the preparation of 14-aryl（alkyl）-14H-dibenzo[a,j]xanthene and 1,8-dioxooctahydroxanthene derivatives by the reaction of aldehydes with 2-naphthol and 5,5-dimethyl-1,3-cyclohexanedione, respectively,in the presence of ZrO（OTf）₂ as a reusable catalyst under solvent-free conditions.In addition,very short reaction times, excellent yields,straightforward procedure,and relatively non-toxicity of the catalyst are other noteworthy advantages of the present method.     

Efficient and direct solid phase synthesis of ketomethylenimino and ketomethylenamino peptides

The aim of this study is the synthesis of pseudopeptides on solid supports, in order to quickly obtain modified peptides. We report a convenient step-by-step synthesis of ketomethylenimino ψ[CO-CHN] and ketomethylenamino ψ[CO-CH₂-NH] peptides. The key is the reaction between the free amino terminus of the supported peptide and a glyoxal-modified amino acid, leading to a ketomethylenimino bond, which can be reduced to a ketomethylenamino bond.     

Use of a highly efficient and recyclable solid-phase catalyst based on nanocrystalline titania for the Pechmann condensation

Nanocrystalline titania-based sulfonic acid was used as an efficient and reusable catalyst for the synthesis of coumarins. The clean, mild acidity condition, the quantitative yields of products, the short reaction time, and the low reaction temperature are attractive features of this method, making it suitable for heat- or acid-sensitive substrates, particularly in drug synthesis. In practice, this method affords an advantageous combination of satisfactory yields, easy product isolation and purification.     

Facile solid phase synthesis of 1,2-disubstituted-6-nitro-1,4-dihydroquinazolines using a tetrafunctional scaffold

Solid phase synthesis of 1, 2-disubstituted-6-nitro-1,4-dihydroquinazolines is described. The new tetrafunctional scaffold N-Alloc-3-amino-3-(2-fluoro-5-nitrophenyl)propionic acid was prepared by nitration of 3-amino-3-(2-fluorophenyl)propionic acid. The scaffold was anchored to Rink resin via its carboxylic group and treated with primary amines to displace the arylfluorine followed by cyclization with aryl isothiocyanates in the presence of DIC upon Alloc deprotection to afford 1,2-disubstituted-6-nitro-1,4-dihydroquinazolines in high yield.     

A simple synthesis of ketone from carboxylic acid using tosyl chloride as an activator

An effective process for the conversion of carboxylic acid to ketone has been discovered. In this process, carboxylic acid has been activated using p-toluene sulphonyl group. Under the optimized condition, aromatic, aliphatic heteroaromatic carboxylic acids have been proved to be good substrates for this methodology. The byproduct of this reaction can be removed very easily during work up process. Also, one equivalent of organometallic reagent is sufficient to complete this transformation.     

Facile synthesis of 2,2,2-trifluoroacetimidoyl chloride derivatives

Several 2,2,2-trifluoroacetimidoyl chlorides have been prepared in a one-pot stage from primary aromatic amines and trifluoroacetic acid. The reactions were carried out with different primary aromatic amines which they contain additional functional groups and good yield were obtained.