Silica‐bonded S‐sulfonic Acid as a Recyclable Catalyst for Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones

2,3‐Dihydroquinazolin‐4(1H)‐one derivatives were synthesized via a one‐pot, three component reaction of isatoic anhydride and an aromatic aldehyde with ammonium acetate or primary amine catalyzed by silica‐bonded S‐sulfonic acid in ethanol at 80°C. The reaction work‐up is simple and the catalyst is easily separated from the products by filtration. The heterogeneous catalyst was recycled for ten runs upon the condensation reaction of isatoic anhydride and 4‐chlorobenzaldehyde with ammonium acetate without losing its catalytic activity.     

Melamine Trisulfunic Acid: An Efficient and Recyclable Solid Acid Catalyst for the Synthesis of 4,4′‐(Arylmethylene)‐bis‐(1H‐pyrazol‐5‐ols)

Melamine trisulfunic acid is employed as a recyclable catalyst for the condensation reaction of aromatic aldehydes with 3‐methyl‐l‐phenyl‐2‐pyrazolin‐5‐one. This condensation reaction was performed in ethanol under refluxing conditions giving 4,4′‐(arylmethylene)‐bis‐(3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐ols) in 80‐96% yields.     

An Efficient Solvent Free Synthesis of 1,8-Dioxo-octahydroxanthene Using p-Toluene Sulfonic Acid

A simple and efficient method for the synthesis of 1,8‐dioxo‐octahydroxanthene by using p‐toluenesulfonic acid as a catalyst under solvent free conditions is described, which involves cyclization of 2,2‐arylmethylenebis(3‐hydroxy‐5,5‐dimethyl‐2‐cyclohexene‐1‐one) that was obtained firstly by the reaction of dimedone with aromatic aldehydes in water as solvent and catalyst at room temperature. The experimental procedures in the two steps are very simple and the products are formed in excellent yields.     

Cu(0)/2,6‐bis(imino)pyridines catalyzed single‐electron transfer‐living radical polymerization of methyl methacrylate initiated with poly(vinylidene fluoride‐co‐chlorotrifluoroethylene)

A series of 2,6‐bis(imino)pyridines, as common ligands for late transition metal catalyst in ethylene coordination polymerization, were successfully employed in single‐electron transfer‐living radical polymerization (SET‐LRP) of methyl methacrylate (MMA) by using poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) (P(VDF‐co‐CTFE)) as macroinitiator with low concentration of copper catalyst under relative mild‐reaction conditions. Well‐controlled polymerization features were observed under varied reaction conditions including reaction temperature, catalyst concentration, as well as monomer amount in feed. The typical side reactions including the chain‐transfer reaction and dehydrochlorination reaction happened on P(VDF‐co‐CTFE) in atom‐transfer radical polymerization process were avoided in current system. The relationship between the catalytic activity and the chemical structure of 2,6‐bis(imino)pyridine ligands was investigated by comparing both the electrochemical properties of Cu(II)/2,6‐bis(imino)pyridine and the kinetic results of SET‐LRP of MMA catalyzed with different ligands. The substitute groups onto N‐binding sites with proper steric bulk and electron donating are desirable for both high‐propagation reaction rate and C? Cl bonds activation capability on P(VDF‐co‐CTFE). The catalytic activity of Cu(0)/2,6‐bis(imino)pyridines is comparable with Cu(0)/2,2′‐bipyridine under the consistent reaction conditions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4378–4388     

Facile one‐pot synthesis of a series of 7‐aryl‐8H‐benzo[h]indeno[1,2‐b]quinoline‐8‐one derivatives catalyzed by cellulose‐based magnetic nanocomposite

A sulfonated magnetic cellulose‐based nanocomposite was applied as an efficient, inexpensive and green catalyst for the one‐pot three‐component synthesis of 7‐aryl‐8H ‐benzo[h ]indeno[1,2‐b ]quinoline‐8‐ones starting from 1,3‐indanedione, aromatic aldehydes and 1‐naphthylamine under solvent‐free conditions in high yields (79–98%) within short reaction times (2–5 min). The nanobiostructure catalyst can be easily separated from the reaction mixture by using an external magnet and reused several times.     

α‐ZrP/Uracil/Cu2+ nanoparticles as an efficient catalyst in the Morita‐Baylis‐Hillman reaction

A facile synthesis of uracil‐Cu²⁺ nanoparticles immobilized on alpha‐zirconium hydrogen phosphate (α‐ZrP), abbreviated as α‐ZrP/Uracil/Cu²⁺, was presented. This compound was synthesized by the thermal method and used as a reusable catalyst for the Morita‐Baylis‐Hillman reaction without any additives. First, (3‐ iodopropyl) trimethoxysilane as a linker is reacted with α‐ZrP support to give the α‐ZrP/IPTMOS. Addition of uracil and then the addition of copper (II) acetate to α‐ZrP/IPTMOS results in the production of selected catalyst. The Morita‐Baylis‐Hillman reaction catalyzed by α‐ZrP/Uracil/Cu^{2 +} demonstrated high product yield, short reaction time and a straightforward work‐up. The catalyst with enough outside surface was easily recovered using centrifugation and reused five times without a significant reduction in its activity.     

Design and characterization of Dendrimer of MNPs as a novel,heterogeneous and reusable nanomagnetic organometallic catalyst for one‐pot synthesis of hydroxyl naphthalene‐1,4‐dione derivatives under solvent‐free conditions

A novel super acidic magnetic nanoparticle as catalyst was successfully synthesized. The preparation of this dendrimer sulfonic acid functionalized γ‐Fe₂O₃ magnetic core‐shell silica nanoparticles as a new recoverable and heterogeneous nanocatalyst was described. The new catalyst was characterized using various techniques such as scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and thermo gravimetric synthesis (TGA). Moreover, we have examined the catalytic activity of the catalyst for one‐pot, efficient and facile synthesis of 2‐hydroxy‐1,4‐naphthoquinone derivatives via a three‐component condensation reaction of 2‐hydroxynaphthalene‐1,4‐dione, aromatic aldehydes and aniline derivatives. High yields of products, short reaction times, waste‐free, mild, ambient and solvent‐free reaction conditions are advantages of this protocol. Also, the catalyst can be easily recovered by an external magnetic and reused several times without significant loss of its catalytic activity.     

One‐Pot Synthesis of 4‐(2,3‐Dihydro‐2‐hydroxy‐1,3‐dioxo‐1H‐inden‐2‐yl)‐Substituted 1‐Aryl‐1H‐pyrazole‐3‐carboxylates via a Tandem Three‐Component Reaction

The hitherto unreported, highly functionalized 1H‐pyrazole‐3‐carboxylates 3 have been synthesized in good yields via a one‐pot three‐component domino reaction of phenylhydrazines, dialkyl acetylenedicarboxylates, and ninhydrin under mild conditions for the first time. No co‐catalyst or activator is required for this multicomponent reaction, and the reaction is, from an experimental point of view, simple to perform (Scheme 1). The structures of compounds 3 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization/addition reaction is proposed (Scheme 2).     

Tin(II) Chloride Dihydrate Catalyzed Groebke Condensation: An Efficient Protocol for the Synthesis of 3-Aminoimidazo[1,2-a]pyridines

The ability of tin(II) chloride dihydrate as a catalyst to promote the three-component condensation reaction from a diversity of aromatic aldehydes, 2-aminopyridines and isonitriles at room temperature is described. This methodology affords a number of 3-aminoimidazo[1,2-a]pyridines in the presence of tin(II) chloride dihydrate as a new and mild Lewis acid catalyst in the multi-component reaction in reasonable yields and short reaction time without any significant optimization of the reaction conditions.     

New bis(N‐heterocyclic carbene) palladium complex immobilized on magnetic nanoparticles: as a magnetic reusable catalyst in Suzuki‐Miyaura cross coupling reaction

A new bis(N ‐heterocyclic carbene) (NHC) palladium complex supported on silica coated magnetic nanoparticles (MNPs) was prepared using the reaction of synthesized Pd‐NHC complex with MNPs. The Pd‐NHC complex was prepared using the reaction of a hydroxyl‐functionalized bis‐imidazolium ionic liquid. The Pd‐NHC organometallic complex was used as a heterogeneous recyclable and active catalyst in the Suzuki‐Miyaura reaction and various aryl halides were coupled with arylboronic acids in order to synthesize diverse biaryls in good to excellent yields. The prepared catalyst was characterized by use of some different microscopic and spectroscopic techniques including elemental analysis, FT‐IR spectroscopy, diffuse reflectance UV–Vis spectrophotometery, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and X‐ray diffraction (XRD). The Pd‐NHC catalyst system is a magnetic reusable catalyst and it can be separated from the reaction mixture using an external magnetic field. The catalyst was reusable in the Suzuki‐Miyaura coupling reaction at least for 6 times without significant decreasing in its catalytic activity.     

A Convenient Method for the Preparation of 1,5‐Diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones

A simple and eco‐friendly method for the preparation of 1,5‐diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones via the cyclo‐condensation reaction of aldehydes, amines and ethyl pyruvate in the presence of silica supported ferric chloride (SiO₂‐FeCl₃) as reusable heterogeneous catalyst is described. The present methodology offers several advantages such as excellent yields, simple procedure and short reaction times.     

Use of an efficient polystyrene‐supported cerium catalyst for one‐pot multicomponent synthesis of spiro‐piperidine derivatives and click reactions in green solvent

One‐pot multicomponent reactions are very demanding in synthetic organic chemistry. Here we report a new polystyrene‐supported cerium catalyst (PS‐Ce‐amtp) obtained via an easy two‐step procedure, which was thoroughly characterized using various techniques. PS‐Ce‐amtp catalyses the environmentally benign one‐pot multicomponent synthesis of spiro‐piperidine derivatives through the reaction of substituted aniline, cyclic active methylene compound and formaldehyde at room temperature. The catalyst also exhibits excellent catalytic activity in one‐pot synthesis of 1,4‐disubstituted 1,2,3‐triazoles via click reaction between in situ generated azides (derived from anilines and amines) and terminal alkynes. The catalyst can be recovered easily after reaction and reused five times without significant loss in its catalytic activity. The advantageous features of this catalyst are atom economy, operational simplicity, short reaction times, easy handling and high recycling efficiency.     

Synthesis of multifunctional polymer containing Ni‐Pd NPs via thiol‐ene reaction for one‐pot cascade reactions

Recently, acid–base bifunctional catalysts have been considered due to their abilities, such as the simultaneous activation of electrophilic and nucleophilic species and their high importance in organic syntheses. However, the synthesis of acid–base catalysts is problematic due to the neutralization of acidic and basic groups. This work reports a facial approach to solve this problem via the synthesis of a novel bifunctional polymer using inexpensive materials and easy methods. In this way, at the first step, heterogeneous poly (styrene sulfonic acid‐n‐vinylimidazole) containing pentaerythritol tetra‐(3‐mercaptopropionate) (PETMP) and trimethylolpropane trimethacrylate (TMPTMA) cross‐linkers were synthesized in the pores of a mesoporous silica structure using click reaction as a novel bifunctional acid–base catalyst. After that, Ni‐Pd nanoparticles supported on poly (styrenesulfonic acid‐n‐vinylimidazole)/KIT‐6 as a novel trifunctional heterogeneous acid–base‐metal catalyst was prepared. The prepared catalysts were characterized by various techniques like FT‐IR, TGA, ICP‐AES, DRS‐UV, TEM, FE‐SEM, EDS‐Mapping, and XRD. The synthesized catalysts were efficiently used as bifunctional/trifunctional catalysts for one‐pot, deacetalization‐Knoevenagel condensation and one‐pot, three‐step and a sequential reaction containing deacetalization‐Knoevenagel condensation‐reduction reaction. It is important to note that the synthesized catalyst showing high chemo‐selectivity for the reduction of nitro group, alkenyl double bond and ester group in the presence of nitrile. Moreover, it was found that the different nanoparticles including Ni, Pd, and alloyed Ni‐Pd showing different chemo‐selectivity and catalytic activity in the reaction.     

Highly Active Copper‐Network Catalyst for the Direct Aldol Reaction

The development of a highly active solid‐phase catechol–copper network catalyst for direct aldol reaction is described. The catalyst was prepared from an alkyl‐chain‐linked bis(catechol) and a copper(II) complex. The direct aldol reaction between carbonyl compounds (aldehydes and ketones) and methyl isocyanoacetate was carried out using 0.1–1 mol % [Cu] catalyst to give the corresponding oxazolines at yields of up to 99 % and a trans/cis ratio of >99:1. The catalyst was reused with no loss of catalytic activity. A plausible reaction pathway is also described.     

Multicomponent Transformation of Isoindoline‐1,3‐diimine (=1H‐Isoindole‐1,3(2H)‐diimine), Acetylenic Esters,and Triphenylphosphine to Novel Dihydropyrimido[2,1‐a]isoindole Derivatives

The three‐component reaction of the zwitterions generated from dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates and triphenylphosphine (Ph₃P) with isoindoline‐1,3‐diimine (=1H‐isoindole‐1,3(2H)‐diimine) is described (Scheme 1). This reaction affords the corresponding special type of substituted dihydropyrimido[2,1‐a]isoindole derivatives in good yields without using any catalyst and activation (Table).     

Magnetite tethered mesoionic carbene‐palladium (II): An efficient and reusable nanomagnetic catalyst for Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling reactions in aqueous medium

In this paper, a highly active, air‐ and moisture‐stable and easily recoverable magnetic nanoparticles tethered mesoionic carbene palladium (II) complex (MNPs‐MIC‐Pd) as nanomagnetic catalyst was successfully synthesized by a simplistic multistep synthesis under aerobic conditions using commercially available inexpensive chemicals for the first time. The synthesized MNPs‐MIC‐Pd nanomagnetic catalyst was in‐depth characterized by numerous physicochemical techniques such as FT‐IR, ICP‐AES, FESEM, EDS, TEM, p‐XRD, XPS, TGA and BET surface area analysis. The prepared MNPs‐MIC‐Pd nanomagnetic catalyst was used to catalyze the Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions and exhibited excellent catalytic activity for various substrates under mild reaction conditions. Moreover, MNPs‐MIC‐Pd nanomagnetic catalyst could be easily and rapidly recovered by applying an external magnet. The recovered MNPs‐MIC‐Pd nanomagnetic catalyst exhibited very good catalytic activity up to ten times in Suzuki–Miyaura and five times in Mizoroki–Heck cross‐coupling reactions without considerable loss of its catalytic activity. However, MNPs‐MIC‐Pd nanomagnetic catalyst shows notable advantages such as heterogeneous nature, efficient catalytic activity, mild reaction conditions, easy magnetic work up and recyclability.     

Microwave‐induced Stereoselectivity in Synthesis of trans‐4‐Aryl‐3‐methyl‐6‐oxo‐4,5,6,7‐tetrahydro‐2H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitriles

A facile synthesis of trans isomers of 4‐aryl‐3‐methyl‐6‐oxo‐4,5,6,7‐tetrahydro ‐ 2H ‐ pyrazolo[3,4‐b]pyridine‐5‐carbonitriles via three‐component condensation reaction of an aldehyde, 3‐amino‐5‐methylpyrazole and ethyl cyanoacetate in acetonitrile has been developed under microwave irradiation. This one‐pot reaction proceeds without any catalyst in short times and gives the product in high selectivities and high yields.     

Regioselective Synthesis of Fused Azo‐linked Pyrazolo[4,3‐e]pyridines Using Nano‐Fe3O4

A multicomponent reaction for the synthesis of fused azo‐linked pyrazolo[4,3‐e]pyridines from 3‐amino‐5‐methylpyrazole, indan‐1,3‐dione and synthesized azo‐linked aldehydes using nano‐Fe₃O₄ as an effective and reusable catalyst is reported. The present methodology offers several advantages, such as a simple procedure with an easy work‐up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.     

One‐Pot,Three‐Component Synthesis of 1‐(2‐Hydroxyethyl)‐1H‐1,2,3‐triazole Derivatives by Copper‐Catalyzed 1,3‐Dipolar Cycloaddition of 2‐Azido Alcohols and Terminal Alkynes under Mild Conditions in Water

A safe, efficient, and improved procedure for the regioselective synthesis of 1‐(2‐hydroxyethyl)‐1H‐1,2,3‐triazole derivatives under ambient conditions is described. Terminal alkynes reacted with oxiranes and NaN₃ in the presence of a copper(I) catalyst, which is prepared by in situ reduction of the copper(II) complex 4 with ascorbic acid, in H₂O. The regioselective reactions exclusively gave the corresponding 1,4‐disubstituted 1H‐1,2,3‐triazoles in good to excellent yields. This procedure avoids the handling of organic azides as they are generated in situ, making this already powerful click process even more user‐friendly and safe. The remarkable features of this protocol are high yields, very short reaction times, a cleaner reaction profile in an environmentally benign solvent (H₂O), its straightforwardness, and the use of nontoxic catalysts. Furthermore, the catalyst could be recovered and recycled by simple filtration of the reaction mixture and reused for ten consecutive trials without significant loss of catalytic activity. No metal‐complex leaching was observed after the consecutive catalytic reactions.     

Microwave Promoted and Improved Thermal Synthesis of Spiro[Indole‐Pyranobenzopyrans] and Spiro[Indole‐Pyranoimidazoles]

Spiro[indole‐pyranoimidazoles] ( 5 ) and spiro[indole‐pyranobenzopyrans] ( 6 ) are readily synthesized in one step in 86–92 and 91–97% yields by the Michael condensation of 3‐dicyanomethylene‐2H‐indol‐2‐ones ( 2 ) with 1‐phenyl‐2‐thiohydantoin ( 3 ) and 4‐hydroxy‐2H‐1‐benzopyran‐2‐one ( 4 ), respectively, without using any catalyst under different reaction conditions (conventional heating and microwave irradiation using (a) polar solvents (b) neutral alumina/silica gel as inorganic solid support in solvent free conditions). 2 was synthesized in situ by the Knoevenagel condensation of indole‐2,3‐dione ( 1 ) and malononitrile in the absence of any catalyst. 100% conversion was observed in most cases on TLC which also showed the formation of a single product. The comparison between the various methods is established.