Tetrabutylammonium bromide (TBAB): a neutral and efficient catalyst for the synthesis of biscoumarin and 3,4-dihydropyrano[c]chromene derivatives in water and solvent-free conditions

A simple, efficient and ecofriendly procedure has been developed using tetrabutylammonium bromide as catalyst for the synthesis of biscoumarin and dihydropyrano[c]chromene derivatives in water and solvent-free neat conditions. The present methodology offers several advantages such as excellent yields, short reaction time and environmentally benign milder reaction conditions.     

Synthesis of biscoumarin and 3,4-dihydropyrano[c]chromene derivatives catalysed by sodium dodecyl sulfate (SDS) in neat water

A simple and efficient one-pot synthesis of biscoumarin and 3,4-dihydropyrano[c]chromene derivatives using catalytic amounts of SDS in water medium is reported. The catalyst can be recovered by simple filtration and reused.     

DABCO promoted one-pot synthesis of dihydropyrano(c)chromene and pyrano[2,3-d]pyrimidine derivatives and their biological activities

A simple and efficient one-pot synthesis of heteroaryl substititued dihydropyrano(c)chromenes and pyrano[2,3-d]pyrimidines has been developed via initial Knoevenagel, subsequent Micheal and final heterocyclization reactions of heteroaryl aldehyde, malononitrile and barbituric acid/ dimedone. 1,4-Diazabicyclo [2.2.2] octane (DABCO) has been used as a catalyst. Short reaction time, environment friendly procedure and excellent yields are the main advantages of this procedure. All synthesized compounds have shown good antimicrobial activity against different microbial stains.     

以淀粉溶液为催化剂锅三组分法合成四氢苯并[b]吡喃和3,4-二氢吡喃并[c]苯并吡喃衍生物简

Tetrahydrobenzo[b]pyran and 3,4-dihydropyrano[c]chromene derivatives were synthesized via a one-pot three-component condensation of aromatic aldehydes with malononitrile and dimedone or 4-hydroxycoumarin in excellent yields in the presence of starch solution as a highly efficient homogenous catalyst. The use of a nontoxic and biodegradable catalyst, simple work-up procedure, and short reaction time are advantages of this method.     

Ag2Cr2O7 nanoparticles: An eco-friendly and reusable catalyst for synthesis of pyrano[c]chromenediones and [1,3]dioxolo[g]chromeneones in aqueous media at ambient temperature

An efficient and green protocol for the synthesis of 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones and 8-aryl-7,8-dihydro-6H-[1,3]dioxolo[4,5-g]chromene-6-ones through the Ag₂Cr₂O₇ nanoparticles catalyzed cyclocondensation reaction of active methylene compounds including 4-hydroxycoumarin or 3,4-methylenedioxyphenol, aromatic aldehydes, and meldrum's acid in water at ambient temperature was described. This method demonstrates several advantages compared with methods that are currently employed such as a mild reaction conditions, simple work-up, good to excellent yields, avoiding toxic catalyst and hazardous solvent, and recovery and reuse of the catalyst.     

Ru(II) complexes bearing tertiary phosphine ligands: a novel and efficient homogeneous catalyst for one‐pot synthesis of dihydropyrano[3,2‐c]chromene and tetrahydrobenzo[b]pyran derivatives

A number of ruthenium complexes were prepared and their catalytic activities in three‐component one‐pot condensation of aldehydes, malononitrile and 4‐hydroxycoumarin or dimedone was considered to afford dihydropyrano[3,2‐c]chromenes and tetrahydrobenzo[b]pyran derivatives under optimum reaction conditions. We found that a catalytic amount of RuBr₂(PPh₃)₄ efficiently promotes the reaction in a short time (3–15 min) and with high yield (75–88%). Copyright © 2012 John Wiley & Sons, Ltd.     

[bmim]OH: An efficient catalyst for the synthesis of mono and bis spirooxindole derivatives in ethanol at room temperature

A rapid and efficient, one pot synthesis of spirooxindole derivatives has been attempted by threecomponent reaction of isatin, malononitrile and carbonyl compound possessing a reactive α-methylene group by using task specific ionic liquid, 1-butyl-3-methyl imidazolium hydroxide [bmim]OH as a catalyst. The important features of this methodology are straight forward route in short reaction time at room temperature and avoid any hazardous organic solvent, toxic catalyst, tedious purification step. Interestingly, this protocol is not only limited to mono-systems but also to the synthesis of newer bisspirooxindole system. The separation of the product and reusability of the catalyst are easy with excellent yield. The [bmim]OH catalyst system could be reused up to five recycles without appreciable loss of activity.     

Magnesium ferrichromate nanoparticles: an efficient and recyclable catalyst in the synthesis of pyrano[2,3-c]pyrazole derivatives

Research on Chemical Intermediates - Magnetically separable magnesium ferrichromate nanoparticles (MgFeCrO4 NPs) were synthesized by aqueous combustion synthesis (ACS) using glycine as the fuel....     

Electrocatalytic one pot synthesis of medicinally relevant 4H-benzo[g]chromene and pyrano[2,3-g]chromene scaffold via multicomponent-domino approach

A highly efficient one pot, multicomponent synthesis of 4H-benzo[g]chromene and pyrano[2,3-g]chromene derivatives are reported by electrochemically stimulated condensation of an aromatic aldehyde, malononitrile and some enolizable acidic compounds in ethanol at room temperature under constant current density. By utilizing common electrode materials and a simple constant current protocol, this method is a new alternative to conventional methods.     

Amberlyst-15: an efficient and reusable catalyst for multi-component synthesis of 3,4-dihydroquinoxalin-2-amine derivatives at room temperature

We demonstrate on the synthesis of multifunctional 3,4-dihydroquinoxalin-2-amine derivatives through a three-component condensation of substituted o-phenylenediamines (OPDA), diverse ketones, and various isocyanides in the presence of an efficient and reusable amberlyst-15 catalyst which was found to be highly active and afforded excellent yields (85-99%) in ethanol at room temperature (2-3 h).     

The condensation of active methylene reagents with salicylaldehyde: Novel synthesis of chromene,azaanthracene, pyrano[3,4‐c]chromene and chromeno[3,4‐c]pyridine derivatives

On heating of the cyanoacetic acid cyclopentylidene hydrazide 1 with salicylaldehyde in the presence of bases the azaanthracene derivative 6 was formed. Also, reaction of 3 with malononitrile and ketones 10a,b afforded the pyrano[3,4‐c]chromene 9 and chromeno[3,4‐c]pyridine 11 respectively. A mechanism for these reactions is proposed.     

PS-TBD triggered general protocol for the synthesis of 4H-chromene,pyrano[4,3-b]pyran and pyrano[3,2-c]chromene derivatives of 1H-pyrazole and their biological activities

A general protocol has been developed for the facile construction of titled derivatives via three component reaction between 3-substituted phenyl-1H-pyrazole-4-carbaldehyde, malononitrile and various Michael donors in presence of 5 mol% polystyrene supported 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene(PS-TBD). PS-TBD was reused for at least five runs with nearly constant catalytic activity. All compounds were screened for antimicrobial and antioxidant activities.     

l-Proline-catalysed one-pot synthesis of tetrahydrobenzo[c]acridin-8(7H)-ones at room temperature

Only 10 mol% of l-Proline in ethanol proved to be a very efficient catalyst for the one-pot synthesis of a wide variety of highly substituted tetrahydrobenzo[c]acridin-8(7H)-ones at room temperature. The key advantages of this process are high yields, cost effectiveness of the catalyst, easy work-up and the products can be directly recrystallized from hot ethanol.     

Multi-component reaction synthesis of novel 3-phenyl-3,4-dihydro-2H-benzo[a][1,3] oxazino[5,6-c]phenazine derivatives catalyzed by reusable ZnO-PTA@Fe3O4/EN-MIL-101(Cr) nanopowder at room temperature

ABSTRACT

A simple, one-pot procedure for the synthesis of novel 3-phenyl-3,4-dihydro-2H-benzo[a][1,3] oxazino[5,6-c]phenazine derivatives by four-component coupling reaction between benzo[a]phenazine-5-ol, formaldehyde and amine in the presence of a catalytic amount ZnO-PTA@Fe₃O₄/EN-MIL-101(Cr) nanopowder in ethanol at room temperature under stirring condition. ZnO-PTA@Fe₃O₄/EN-MIL-101(Cr) An inorganic magnetic catalyst was analyzes and described by the XRD, TEM, FESEM, TGA, AFM, VSM and ICP-OES. This study presents simple, efficient, and one-pot multicomponent protocol, which provides several advantages such as short reaction times, high yields, easy working up, chromatography-free technique, catalyst recovery, and reusability are other highlights of this work.     

Synthesis of functionalized chromene and spirochromenes using l-proline-melamine as highly efficient and recyclable homogeneous catalyst at room temperature

An efficient and recyclable homogeneous catalyst is developed using commercially cheap l-proline and melamine for the synthesis of chromenes and spirochromenes (spirooxindoles) via multicomponent reactions at room temperature. Systematic studies were conducted in order to achieve desired reactivity and recyclability of the catalyst using various α-amino acids and aromatic amines as donor-acceptor pairs. Among the screened combinations, l-proline and melamine (3:1 ratio; 3 mol% on total weight) was found to be best catalyst to give the desired products with excellent yields (up to 99%) in very short times (1–15 min) at room temperature in DMSO as solvent. The catalyst was recovered by adding EtOAc and reused up to 5 cycles without losing the catalytic activity.     

Citric acid:An efficient and green catalyst for rapid one pot synthesis of quinoxaline derivatives at room temperature

The condensation of o-phenylenediamines with 1,2-dicarbonyl compounds in the presence of citric acid afforded the corresponding quinoxaline derivatives in higher yields at room temperature in ethanol,and most of the reactions were completed in less than 1 min.     

DABCO-catalyzed multi-component domino reactions for green and efficient synthesis of novel 3-oxo-3H-benzo[a]pyrano[2, 3-c] phenazine-1-carboxylate and 3-(5-hydroxybenzo[a]phenazin-6-yl) acrylate derivatives in water

An efficient, convenient and environmentally benign procedure for the synthesis of novel 3-oxo-3H-benzo[a]pyrano[2,3-c]phenazine-1-carboxylate and 3-(5-hydroxybenzo[a]phenazin-6-yl)acrylate derivatives has been developed by domino three-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamines and acetylenic esters in the presence of a catalytic amount of DABCO as an expedient, eco-friendly and reusable base catalyst in water. This green process produces biologically and pharmacologically significant heterocycles in a one-pot single operation and offers considerable advantages such as:operational simplicity, short reaction time, high yields, reusability of catalyst, absence of any tedious workup or purification and avoids hazardous reagents/solvents.     

Sulfamic acid as a recyclable and green catalyst for rapid and highly efficient synthesis of 2-arylbenzothiazoles in water at room temperature

2-Arylbenzothiazoles have been synthesized in water in good to excellent yield from direct condensation of various aromatic aldehydes with 2-aminothiophenol promoted by catalytic amount of sulfamic acid at room temperature. This method provides a simple, rapid and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst and simple work-up procedure.