Magnetic Nanoparticle Supported Ionic Liquid Assisted Green Synthesis of Pyrazolopyranopyrimidines and 1,6‐diamino‐2‐oxo‐1,2,3,4‐tetrahydropyridine‐3,5‐ dicarbonitriles

A simple and eco‐friendly green protocol was used for synthesis of pyrazolopyranopyrimidines via four‐component reaction of hydrazine hydrate, ethyl acetoacetate, barbituric acid or dimethyl barbituric acid, and aromatic aldehydes under thermal and solvent‐free conditions in the presence of magnetic nanoparticle supported silica bonded n‐propyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane chloride (MNPs@DABCO⁺Cl^?) as an efficient, recyclable heterogeneous catalyst. MNPs@DABCO⁺Cl^? also catalyzed the synthesis of 1,6‐diamino‐2‐oxo‐1,2,3,4‐tetrahydropyridine‐3,5‐dicarbonitrile derivatives by four‐component reaction of hydrazine hydrate, malononitrile, ethyl cyanoacetate and ketones under thermal and solvent‐free conditions at 80 °C. These methods are practical and offer many advantages, such as high yields, short reaction times, and simple work‐up.     

Ferrocene‐tagged ionic liquid stabilized on silica‐coated magnetic nanoparticles: Efficient catalyst for the synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions

An advanced novel magnetic ionic liquid based on imidazolium tagged with ferrocene, a supported ionic liquid, is introduced as a recyclable heterogeneous catalyst. Catalytic activity of the novel nanocatalyst was investigated in one‐pot three‐component reactions of various aldehydes, malononitrile and 2‐naphthol for the facile synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions without additional co‐catalyst or additive in air. For this purpose, we firstly synthesized and investigated 1‐(4‐ferrocenylbutyl)‐3‐methylimidazolium acetate, [FcBuMeIm][OAc], as a novel basic ferrocene‐tagged ionic liquid. This ferrocene‐tagged ionic liquid was then linked to silica‐coated nano‐Fe₃O₄ to afford a novel heterogeneous magnetic nanocatalyst, namely [Fe₃O₄@SiO₂@Im‐Fc][OAc]. The synthesized novel catalyst was characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, and transmission and field emission scanning electron microscopies. Combination of some unique characteristics of ferrocene and the supported ionic liquid developed the catalytic activity in a simple, efficient, green and eco‐friendly protocol. The catalyst could be reused several times without loss of activity.     

Fe3O4@SiO2@sulfated boric acid as superparamagnetic and recyclable nanocatalyst‐assisted,one‐pot,pseudo four‐component synthesis of 5‐amino‐2‐aryl‐3H‐chromeno[4,3,2‐de][1,6]naphthyridine‐4‐carbonitrile derivatives

The catalytic performance of the superparamagnetic nanocatalyst Fe₃O₄@SiO₂@Sulfated boric acid as a green, recyclable, and acidic solid catalyst in the synthesis of chromeno[4,3,2‐de][1,6]naphthyridine derivatives has been studied. Chromeno[4,3,2‐de][1,6]naphthyridine derivatives via a pseudo four‐component reaction from aromatic aldehydes (1 mmol), malononitrile (2 mmol), and 2′‐hydroxyacetophenone in the presence of Fe₃O₄@SiO₂@Sulfated boric acid (0.004 g) as a nanocatalyst in 3 mL of water as a green solvent at 80°C has been synthesized. The advantages of this method are higher product yields in shorter reaction times, easy recyclability and reusability of the catalyst, and easy work‐up procedures. The nanocatalyst was reused at least six times. The nanocatalyst retained its stability in the reaction, and after reusability, it was separated easily from the reaction by an external magnet.     

Ultrasound‐Assisted Synthesis of 6‐Methyl‐1,2,3,4‐tetrahydro‐N‐aryl‐2‐oxo/thio‐4‐arylpyrimidine‐5‐carboxamides Catalyzed by Uranyl Nitrate Hexahydrate

An efficient and simple method developed for the synthesis of 6‐methyl‐1,2,3,4‐tetrahydro‐N‐aryl‐2‐oxo/thio‐4‐arylpyrimidine‐5‐carboxamide derivatives ( 4a‐o ) using UO₂(NO₃)₂.6H₂O catalyst under conventional and ultrasonic conditions. The ultrasound irradiation synthesis had shown several advantages such as milder conditions, shorter reaction times and higher yields. The structures of all the newly synthesized compounds have been confirmed by FT‐IR, ¹H NMR, ¹³C NMR and mass spectra.     

Bifunctional Heterogeneous Catalysis of Silica–Alumina‐Supported Tertiary Amines with Controlled Acid–Base Interactions for Efficient 1,4‐Addition Reactions

We report the first tunable bifunctional surface of silica–alumina‐supported tertiary amines (SA–NEt₂) active for catalytic 1,4‐addition reactions of nitroalkanes and thiols to electron‐deficient alkenes. The 1,4‐addition reaction of nitroalkanes to electron‐deficient alkenes is one of the most useful carbon–carbon bond‐forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA‐supported amine (SA–NEt₂) catalyst enabled selective formation of a double‐alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA–NEt₂ catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA–NEt₂ catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron‐deficient alkenes. The solid‐state magic‐angle spinning (MAS) NMR spectroscopic analyses, including variable‐contact‐time ¹³C cross‐polarization (CP)/MAS NMR spectroscopy, revealed that acid–base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid–base interactions.     

Green synthesis of 3,4-dihydropyrimidinones using nano Fe3O4@meglumine sulfonic acid as a new efficient solid acid catalyst under microwave irradiation

Design, synthesis and characterization of nano Fe₃O₄@meglumine sulfonic acid as a new solid acid catalyst for the simple and green one pot multicomponent synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones was studied. New solid acid catalyst was prepared through a clean and simple protocol and characterized using FTIR, VSM, TGA, SEM, elemental analysis (CHN) and XRD techniques. Heterogenization of homogeneous catalyst as a green approach is a useful method for enhancing the efficiency of catalyst. Presented study was a new method for attachment of homogeneous highly soluble catalyst (meglumine sulfate) to the magnetite nanoparticle surfaces for preparing a heterogeneous and effective catalyst. Obtained heterogeneous and reusable solid acid catalyst has high performance in the synthesis of Biginelli compounds. The reaction was performed under microwave irradiation as a rapid and green condition. Easy work up as well as excellent yield (90–98%) of products in short reaction times (40–200 s) and reusable catalyst are the main advantages of presented procedure. Reaction products were characterized in details using physical and chemical techniques such as melting point, ¹H NMR, ¹³C NMR and FTIR.     

Application of Sulfonic Acid Functionalized SBA‐15 as a New Nanoporous Acid Catalyst in the Green One‐Pot Synthesis of Spirooxindole‐4H‐pyrans

Sulfonic acid functionalized SBA‐15 (SBA‐Pr‐SO₃H) as a new nanoporous solid acid catalyst was applied in the green one‐pot synthesis of spirooxindole‐4H‐pyrans via condensation of isatins, malononitrile or methyl cyanoacetate or ethyl cyanoacetate, and 4‐hydroxycoumarin in water solvent. SBA‐Pr‐SO₃H was proved to be an efficient heterogeneous nanoporous solid acid catalyst with a pore size of 6 nm that could be easily handled and removed from the reaction mixture by simple filtration and can be recovered and reused for several times without any loss of activity. The significant merits of present methodology are its simplicity, short reaction time, good yields, and environmentally benign mild reaction condition as water was used as a green solvent.     

Synthesis of Ethyl 2‐Amino‐4‐benzoyl‐5‐oxo‐5,6‐dihydro‐4H‐pyrano[3,2‐c]quinoline‐3‐carboxylates by a One‐pot,Three‐Component Reaction in the Presence of TPAB

In this research, in order to synthesize a series of ethyl 2‐amino‐4‐benzoyl‐5‐oxo‐5,6‐dihydro‐4H‐pyrano[3,2‐c]quinoline‐3‐carboxylates, a green and an efficient method is proposed through one‐pot three‐component reaction of substituted arylglyoxals, ethyl cyanoacetate, and 4‐hydroxyquinolin‐2(1H)‐one in the presence of terapropylammonium bromide as a catalyst in good yields. All synthesized new substances were characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectral data and elemental analysis.     

Co(II) anchored glutaraldehyde crosslinked magnetic chitosan nanoparticles (MCS) for synthesis of 2,4,5‐trisubstituted and 1,2,4,5‐tetrasubstituted imidazoles

A simple, highly efficient and green synthesis of 2,4,5‐trisubsituted and 1,2,4,5‐tetrasubstituted imidazoles was developed using a novel MCS‐GT@Co(II) magnetically recoverable and recyclable catalyst under refluxing conditions with ethanol as a solvent. The catalyst was prepared by immobilization of chitosan onto Fe₃O₄ using glutaraldehyde as crosslinker followed by Co(II) ion immobilization via cobalt acetate. The catalyst was characterized using various techniques. For organic products determination, ¹H NMR, ¹³C NMR and Fourier transform infrared spectroscopies were used. The reaction was also tried with individual components of the catalyst, but the synergistic effect of the components in the prepared catalyst showed the highest yield and shortest reaction time.     

Copper‐supported β‐cyclodextrin‐functionalized magnetic nanoparticles: Efficient multifunctional catalyst for one‐pot ‘green’ synthesis of 1,2,3‐triazolylquinazolinone derivatives

The green synthesis of 2‐(4‐((1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)oxy)phenyl)quinazolin‐4(3H)‐one derivatives is reported. The catalyst for this synthesis is copper‐supported β‐cyclodextrin‐functionalized magnetic silica–iron oxide nanoparticles ([Cu@BCD@SiO₂@SPION]). [Cu@BCD@SiO₂@SPION] simultaneously catalyses ‘click’ reaction, oxidation of C? N bond and multicomponent reaction. The desired 1,2,3‐triazolylquinazolinone product is easily obtained in water at room temperature under mild reaction conditions. Another advantage of the catalyst is its reusability. It can simply be isolated using an external magnet and reused in reactions with no significant decrease in catalyst efficiency. Transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometry and Fourier transform infrared spectroscopy are used for exact characterization of the [Cu@BCD@SiO₂@SPION] catalyst.     

Chemoselective Route for Synthesis of N‐Aryl‐3‐oxochromeno[2,3‐c]pyrazole‐2(3H)‐carbothioamide Derivatives

A chemoselective route for the synthesis of chromeno[2,3‐c]pyrazole‐2(3H)‐carbothioamide derivatives by a five‐component reaction of salicylaldehyde, malononitrile, NH₂NH₂?H₂O, aryl isothiocyanate, and H₂O in EtOH/AcOH mixture is reported. This new protocol has the advantages of high yields, short reaction times, ease of operation, and simple purification. All structures were confirmed by IR, ¹H‐ and ¹³C‐NMR, and MS analyses. A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Silica Gel‐Supported Polyphosphoric Acid (PPA/SiO2): An Efficient and Reusable Heterogeneous Catalyst for Facile Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐free Conditions

A simple, efficient and green method for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes by a one‐pot condensation reaction of β‐naphthol and aryl aldehydes using silica gel‐supported polyphosphoric acid (PPA/SiO₂), an effective and reusable catalyst, under solvent‐free conditions is described. 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.     

An Efficient Synthesis of 1′,7′,8′,9′‐Tetrahydrospiro[indoline‐3,4′‐pyrazolo[3,4‐b]quinoline]‐2,5′(6′H)‐dione Derivatives in Aqueous Medium

An efficient and green reactions of isatins, 3‐amine‐1H‐pyrazole (5‐methyl‐1H‐pyrazol‐3‐amine) and 1,3‐diketone in aqueous medium for the synthesis of novel 1′,7′,8′,9′‐tetrahydrospiro[indoline‐3,4′‐pyrazolo[3,4‐b]quinoline]‐2,5′(6′H)‐dione derivatives were reported in this research. The advantages of this reaction are simple operation, mild‐reaction conditions, wide scope substrate, high yields, and friendly environment. The products were confirmed by IR, ¹H NMR, ¹³C NMR, and HRMS.     

Solid‐State Synthesis and Characterization of 2‐Thioxo‐4‐Imidazolidinone Derivatives

A new and efficient two‐step solid‐state synthesis method is described for 2‐thioxo‐4‐imidazolidinone from aryl isothiocyanate and free amino acid. This method requires only simple equipment and is easy to perform. The products reported were characterized on the basis of IR, MS, ¹H NMR, ¹³C NMR and elemental analysis.     

Green Synthesis of 1‐(1,2,4‐Triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)indole]‐2′,4′(1′H)‐diones as Potential Insecticidal Agents

One pot green synthesis of 1‐(1,2,4‐triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)‐indole]‐2′,4′(1′H)‐diones was carried out by the reaction of indole‐2,3‐diones,4‐amino‐4H‐1,2,4‐triazole and acetyl chloride/chloroacetyl chloride in ionic liquid [bmim]PF₆ with/without using a catalyst. It was also prepared by conventional method via Schiff's bases, 3‐[4H‐1,2,4‐triazol‐4‐yl]imino‐indol‐2‐one. Further, the corresponding phenoxy derivatives were obtained by the reaction of chloro group attached to azetidine ring with phenols. The synthesized compounds were characterized by analytical and spectral (IR, ¹H NMR, ¹³C NMR, and FAB mass) data. Evaluation for insecticidal activity against Periplaneta americana exhibited promising results.     

HAp‐encapsulated γ‐Fe2O3‐supported dual acidic heterogeneous catalyst for highly efficient one‐pot synthesis of benzoxanthenones and 3‐pyranylindoles

A novel method is reported for the synthesis of benzoxanthenone and 3‐pyranylindole derivatives via one‐pot three‐component reactions using a newly synthesized HAp‐encapsulated γ‐Fe₂O₃‐supported dual acidic heterogeneous catalyst, as a reusable and highly efficient nanocatalyst. In this protocol the use of the nanocatalyst provided a green, useful and rapid method to generate products in short reaction times (4–20 min) and in excellent yields (87–96%). The paramagnetic nature of the catalyst provided a simple, trouble‐free and facile approach for the separation of the catalyst by applying an external magnet, and it could be used in eight cycles without significant loss in catalytic efficiency.     

Enantioselective Divergent Synthesis of (−)‐cis‐α‐ and (−)‐cis‐γ‐Irone by Using Wilkinson’s Catalyst

A simple, efficient synthesis is reported for (?)‐cis‐α‐ and (?)‐cis‐γ‐irone, two precious constituents of iris oils, in ≥99 % diastereomeric and enantioselective ratios. The two routes diverge from a common intermediate prepared from (?)‐epoxygeraniol. Of general interest in this approach is the installation of the enone moiety of irones through a NHC?Au^I‐catalyzed Meyer–Schuster‐like rearrangement of a propargylic benzoate and the use of Wilkinson’s catalyst for the stereoselective hydrogenation of a prostereogenic exocyclic double bond to secure the critical cis stereochemistry of the alkyl groups at C2 and C6 of the irones. The stereochemical aspects of this reaction are rationally supported by DFT calculation of the conformers of the substrates undergoing the hydrogenation and by a modeling study of the geometry of the rhodium η² complexes involved in the diastereodifferentiation of the double bond faces. Thus, computational investigation of the η² intermediates formed in the catalytic cycle of prostereogenic alkene hydrogenation by using Wilkinson’s catalyst could be highly predictive of the stereochemistry of the products.     

Unexpected Spiroproducts from the Reaction of N‐Benzoylglycine with Ortho‐Formylbenzoic Acids −3,5′‐Dioxo‐2′‐Phenyl‐1,3‐Dihydrospiro[Indene‐2,4′‐[1,3]Oxazol]‐1‐yl Acetates: Establishments of Their Structure

This paper describes a method of preparation of new 3,5′‐dioxo‐2′‐phenyl‐1,3‐dihydrospiro[indene‐2,4′‐[1,3]oxazol]‐1‐yl acetate and its 5‐chloro‐ and bromoderivatives as products of interaction of N‐benzoylglycine (hippuric acid) with corresponding ortho‐formylbenzoic acids. The reaction carried out in acetic anhydride media in the presence of piperidine as catalyst. The novel spirocompounds were purified by column chromatography from multicomponent reaction mixtures. The composition of the spiro‐products was confirmed by C, H, N element analysis. The structure was established by IR, MS, ¹H‐ and ¹³C‐NMR analysis including COSY ¹H‐¹³C experiments.     

Synthesis of α‐Aminonitriles and 5‐Substituted 1H‐Tetrazoles Using an Efficient Nanocatalyst of Fe3O4@SiO2–APTES‐supported Trifluoroacetic Acid

Fe₃O₄@SiO₂–APTES‐supported trifluoroacetic acid nanocatalyst was used for the one‐pot synthesis of α‐aminonitriles via a three‐component reaction of aldehydes (or ketones), amines, and sodium cyanide. This method produced a high yield of 75–96% using only a small amount of the catalyst (0.05 g) in EtOH at room temperature. The catalyst was also employed for the synthesis of 5‐substituted 1H‐tetrazoles from nitriles and sodium azide in EtOH at 80°C. The tetrazoles were produced with good‐to‐excellent yields in a short reaction time of 4 h. Both synthetic methods were carried out in the absence of an organic volatile solvent. Because the supported trifluoroacetic acid generated a solid acid on the surface, thus the acid corrosiveness was not a serious challenge. This heterogeneous nanocatalyst was magnetically recovered and reused several times without significant loss of catalytic activity.     

Synthesis of 12‐aryl‐12H‐benzo[i][1,3]‐dioxolo[4,5‐b]xanthene‐6,11‐diones using silica sulfuric acid as an efficient and versatile catalyst under solvent‐free conditions

Some novel 12‐aryl‐12H‐benzo[i][1,3]‐dioxolo[4,5‐b]xanthene‐6,11‐diones can be rapidly and efficiently synthesized in excellent yields by condensing a variety of aldehydes with 3,4‐methylenedioxyphenol and 2‐hydroxy‐1,4‐naphthoquinone in the presence of a catalytic amount of silica sulfuric acid under solvent‐free conditions. The simple experimental procedure, solvent‐free reaction conditions, utilization of an inexpensive and readily available catalyst, short period of conversion, and excellent yields are the advantages of the present method. Furthermore, the catalyst can be recycled and reused three times without significant loss of activity. The structures of the novel compounds are confirmed by IR, ¹H‐NMR, ¹³C‐NMR, MS, and elemental analysis. J. Heterocyclic Chem., 2011.