Hydroxyl ammonium ionic liquid-catalyzed simple and efficient synthesis of 5-arylidene-2,4-thiazolidinediones under solvent-free conditions

A simple and efficient synthesis of 5-arylidene-2,4-thiazolidinediones by the Knoevenagel condensation of aldehydes with 2,4-thiazolidinedione in the presence of 2-hydroxy ethylammonium propionate under solvent-free conditions is described. The attractive features of this procedure are operational simplicity, high yields, short reaction times, easy to prepare the catalyst, mild and environmentally benign reaction conditions, and recycle of the catalyst.     

An efficient method for Knoevenagel condensation: a facile synthesis of 5-arylidenyl 2,4-thiazolidinedione

Abstract

Knoevenagel condensation of various aromatic aldehydes with 2,4-thiazolidinedione has been carried out in polyethylene glycol-300. The reactions were carried out at moderate temperature with very simple isolation procedure and with better yields.     

Mn-MOF@Pi composite: synthesis,characterisation and an efficient catalyst for the Knoevenagel condensation reaction

We have synthesised new Mn-MOF@Pi composite by encapsulation of piperidine in desolvated Mn-MOF and investigated its catalytic performance in Knoevenagel condensation reaction. The newly developed composite is compatible with various aromatic aldehydes and converting them to the desired Knoevenagel condensation products in good yields and selectivity. Furthermore, composite Mn-MOF@Pi is reusable and shows good catalytic activity than native MOF.     

Alum catalyzed simple and efficient synthesis of 5-arylidene-2,4-thiazolidinedione in aqueous media

Abstract

Alum (KAl(SO₄)₂·12H₂O) is an inexpensive, efficient, and non-toxic catalyst used for the synthesis of 5-arylidine-2,4-thiazolidinediones by the Knoevenagel condensation of aromatic aldehydes with 2,4-thiazolidinedione in aqueous media at 90°C. This method affords the 5-arylidine-2,4-thiazolidinediones in short reaction times, high yields, and green aspects by avoiding toxic catalysts and hazardous solvents.     

TsOH-SiO2 as an efficient and eco-friendly catalyst for Knoevenagel condensation

Tosic acid on silica gel (TsOH-SiO₂) was synthesized and characterized using microscopic and spectroscopic techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Thermal behaviour of the catalyst was investigated by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. TsOH-SiO₂ showed excellent catalytic activity for the Knoevenagel condensation and was recyclable for six cycles.     

Lithium hydroxide: A simple and an efficient catalyst for Knoevenagel condensation under solvent-free Grindstone method

Synthesis of arylmethylidenes from araldehydes and active methylene compounds catalyzed by catalytic amount of lithium hydroxide (LiOH·H₂O) in the absence of a solvent under Grindstone method is reported. The reactions go to completion within 1–5 min and give products in excellent yields at 26 °C.     

Cellulose sulphuric acid as a biodegradable and reusable catalyst for the Knoevenagel condensation

A green, mild and efficient method for Knoevenagel condensation of 3-formylchromone/2-chlroquinoline-3-carbaldehyde with active methylene compounds such as Meldrum’s acid/ethyl cyanoacetate using biosupported cellulose sulphuric acid (CSA) in the solid-state by grinding under solvent-free condition has been developed. This method provides several advantages including environmental friendliness, shor t reaction times, high yields and a simple work-up procedure. Moreover, the CSA was successfully reused for four cycles without significant loss of activity.     

NH4Cl/Zn powder: An efficient,chemoselective reducing catalyst for the microwave-assisted synthesis of 2,3-disubstituted quinolines via tandem Knoevenagel condensation

An efficient, a hitherto unreported, sustainable, and environmentally friendly microwave-assisted synthesis of 2,3-disubstituted quinolines by reductive cyclization of 2-nitrobenzaldehydes and various active methylene compounds via tandem Knoevenagel condensation promoted by an efficient eco-friendly, chemoselective reducing catalyst ammonium chloride (NH₄Cl) and zinc powder was developed. This present methodology is a mild, green, efficient, and environmentally benign process as it eliminates the harsh reaction conditions, non-volatile solvents, relatively expensive reagents, high catalyst loading, and also provides a number of other benefits like fast synthesis, simple reaction set-up, and good to the excellent yield of the products.     

Zeolite an efficient catalyst for the Biginelli condensation reaction

A zeolite catalyzed, single step and environmentally friendly process for synthesis of classical Biginelli reaction was investigated. For this reaction Transition metal/Y zeolites were prepared by microwave solid-state and aqueous solution ion-exchange methods. The yield of reactions was increased in order of CuY > CoY > NiY > MnY ≈ FeY > VY > CrY > ZnY for the solid-state zeolite ion-exchange and CuY > CoY > NiY > MnY > CrY > VY > ZnY > FeY for the aqueous solution ion-exchange. The solid-state ion-exchange zeolite by microwave irradiation showed higher activity compared to the aqueous solution exchange. The yield of the product in the present of CuY zeolite was in order of 22–50%.     

An efficient synthesis of propargylamines using a silica gel anchored copper chloride catalyst in an aqueous medium

The design and development of a silica gel anchored copper chloride heterogeneous catalyst for the synthesis of propargylamines using an amine, an aldehyde, and an alkyne through C-H activation in water is described. Both aliphatic and aromatic aldehydes and amines are used for the reaction. The catalyst was recovered quantitatively by simple filtration and reused several times.     

Solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids via an intramolecular Knoevenagel condensation

A solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids is described. The products are formed in a two-step synthesis in which ortho-aminophenones are first coupled to malonic acid bound to the Wang Resin followed by ring closure via an intramolecular Knoevenagel condensation.     

Choline hydroxide: An efficient and biodegradable catalyst for the synthesis of 2-amino-3-nitro-4H-chromene derivatives in an aqueous medium

Abstract

An expedient, eco-friendly and efficient procedure for the synthesis of novel 2-amino-3-nitro-4H-chromene derivatives has been developed through the reaction of various 2-hydroxybenzaldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine in the presence of the basic ionic liquid catalyst (choline hydroxide (ChOH)) at room temperature an aqueous medium. The advantageous of this method is a biodegradable and recyclable catalyst, mild, environmentally friendly and high products yields (83-96%) in short reaction times.     

Catalyst-free,aqueous and highly diastereoselective synthesis of new 5-substituted 1H-tetrazoles via a multi-component domino Knoevenagel condensation/1,3 dipolar cycloaddition reaction

An approach for the synthesis of new 5-substituted-tetrazoles via multi-component domino Knoevenagel condensation/1,3 dipolar cycloaddition reaction of carbonyl compounds, malononitrile and sodium azide in water without assistance of any catalyst has been reported. This general protocol provides a wide variety of 5-substituted 1H-tetrazoles in good yields under mild reaction conditions.     

Magnetic nanoparticle supported amine: An efficient and environmental benign catalyst for versatile Knoevenagel condensation under ultrasound irradiation

Amine functionalized silica coated Fe₃O₄ nanoparticles (SiO₂@MNP-A) were successfully prepared as a novel heterogeneous amine. The catalyst was characterized by XRD, FT-IR, TEM, magnetic measurement, elemental analysis and was found to be a magnetically separable and highly active catalyst for ambient Knoevenagel condensation of aromatic aldehydes and α-aromatic (heteroaromatic or polyaromatic)-substituted methylene compounds in water under ultrasonic irradiation to afford the corresponding products in good to excellent yields. Very interestingly, SiO₂@MNP-A successfully catalyze the reaction of the non-cyano substituted compound with benzaldehyde to achieve a key intermediate for the preparation of Atorvastatin calcium in green and atom-economic manner. In addition, the catalyst SiO₂@MNP-A can be reused for 8 times without any obvious loss of its activity. The role of ultrasonication in the Knoevenagel condensation was also discussed with the assistance of UV–vis spectrometry.     

Nano indium oxide: an efficient catalyst for the synthesis of 1,2-disubstituted benzimidazoles in aqueous media

Synthesis of 1,2-disubstituted benzimidazoles has been developed by the condensation of diamine with aldehydes using nano In₂O₃ as an efficient catalyst under mild reaction conditions in aqueous media. The procedure is applicable to aryl, aliphatic, heteroaryl aldehydes. In₂O₃ nanoparticles are recyclable without the loss of significant catalytic activity.     

Electrogenerated acid as an efficient catalyst for the preparation of 5-hydroxymethylfurfural

A new method for the synthesis of 5-hydroxymethylfurfural (HMF) with high yields in dimethyl sulfoxide (DMSO) is presented. By using constant-current electrolysis more than 90% of sucrose or fructose was converted to HMF at room temperature in DMSO in the presence of traces of water.     

Sevelamer as an efficient and reusable heterogeneous catalyst for the Knoevenagel reaction in water

A catalyst system of Sevelamer, a phosphate-binding drug, has been prepared and used in the Knoevenagel reaction of aromatic aldehydes in water to produce substituted electrophilic alkenes. The products were obtained in excellent yields. Several novel, related catalytic systems showed promising catalytic properties for aromatic and heterocyclic aldehydes. The Sevelamer catalyst can be recovered using simple filtration and reused numerous times（up to 15 times） in the aqueous Knoevenagel reaction without any significant lowering of activity.     

An efficient synthesis of 9-anthrone lactone derivatives via the Knoevenagel condensation and intramolecular cyclization

One-step synthesis of 9-anthrone lactone derivatives from 1-acetyloxyanthraquinone with a variety of dicarbonyl substrates in the presence of K₂CO₃ by Knovenagel condensation and intramolecular cyclization is developed. Possible reaction mechanisms have been investigated using the density functional theory (DFT), which has been widely used in the study of reaction mechanism. The strategy could be useful for the synthesis of the core structure of marine natural product aspergiolide.