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....     

Polyethylene glycol-promoted synthesis of pyrimido[1,2-a]benzimidazole and pyrano[2,3-c]pyrazole derivatives in water

Synthesis of pyrimido[1,2-a]benzimidazole and pyrano[2,3-c]pyrazole derivatives were achieved using polyethylene glycol (PEG-400) as promoting reaction medium in water under catalyst-free conditions at reflux and room temperature, respectively. The structure of pyrimido[1,2-a]benzimidazole was confirmed using ¹H NMR, ¹³C NMR, DEPT, and HMBC experiments. The promising points for the present methodology are efficiency, generality, high yield, short reaction time, cleaner reaction profile, ease of product isolation, simplicity, potential of recycling reaction medium, and finally agreement with green chemistry protocols.     

Synthesis and characterization of Fe3O4@THAM-SO3H as a highly reusable nanocatalyst and its application for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives

In this work, a new, green and beneficial nanomagnetic catalyst was easily fabricated using sulfuric acid as an acidic group on Fe₃O₄ nanoparticles coated with tris (hydroxymethyl) aminomethane (THAM). The synthesized catalyst was characterized by FT-IR, TGA/DTG, XRD, TEM, EDS, VSM, and SEM analyses. Next, its catalytic activity was studied for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives. This catalyst has advantages such as high catalytic activity, non-toxicity, easy separation from the reaction mixture using an external magnet and reuses for several times without significantly reducing in its catalytic activity.     

H14[NaP5W30O110] catalyzed one-pot three-component synthesis of dihydropyrano[2,3-c]pyrazole and pyrano[2,3-d]pyrimidine derivatives

This is a report of an efficient, clean and facile method for the synthesis of 1,4-dihydropyrano[2,3-c] pyrazole and pyrano[2,3- d]pyrimidine derivatives via three-component one-pot condensation of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one or barbituric acid, aldehydes and malononitrile in the presence of a catalytic amount of preyssler type heteropolyacid as a green and reusable catalyst in water or ethanol under refluxing conditions.     

Silica-coated magnetic NiFe2O4 nanoparticles-supported H3PW12O40; synthesis,preparation, and application as an efficient,magnetic, green catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives

Research on Chemical Intermediates - A powerful, magnetic, supported, acid catalyst, NiFe2O4@SiO2–H3PW12O40, was prepared by chemical support of Keggin (H3PW12O40) heteropolyacid (HPA) on...     

微波辐射一步法合成吡喃和吡喃[2, 3-c]吡唑衍生物

芳醛、丙二腈与5,5-二甲基-1,3-环己二酮或3-甲基-1-苯基-2-吡唑啉-5-酮在乙醇溶剂中用哌啶作催化剂,经微波辐射一步合成了2-氨基-3-氰基-4-芳基-7,7-二甲基-5-氧代-5,6,7,8-四氢苯并吡喃和6-氨基-5-氰基-4-芳基-1,4-二氢吡喃[2,3-c]吡唑,反应在2～12min内完成,产率53%～91%。     

Naphtho[1′,2′:5,6] pyrano[2,3-c] pyrazole derivatives

Reaction of 1-oxo-3-dialkylamino-1 H-naphtho[2,1-b]pyrans with N,N-dimethylformamide in the presence of phosphorus oxychloride afforded the corresponding 1-oxo-2-formyl-3-dialkyl-amino-1H-naphtho[2,1-b]pyrans. Condensation of 1-oxo-2-formyl-3-dimethylamino-1H-naphtho[2,1-b]pyran with hydrazine or monosubstituted hydrazines was found to lead to the formation of 8-alkyl(aryl)-1 1-oxo-8H,1 1H-naplitho[1′,2′:5,6] pyrano[2,3-c]pyrazoles through the intermediate hydrazones and subsequent cyclization. The same result was achieved starting from other 3-dialkylamino derivatives but in a lower yield.     

Nano silica extracted from horsetail plant as a natural silica support for the synthesis of H3PW12O40 immobilized on aminated magnetic nanoparticles (Fe3O4@SiO2-EP-NH-HPA): a novel and efficient heterogeneous nanocatalyst for the green one-pot synthesis of pyrano[2,3-c]pyrazole derivatives

Research on Chemical Intermediates - In this work, nanomesoporous silica has been prepared from horsetail (Equisetum arvense), which is a medicinal plant, with high surface area. This natural...     

[DBU][Ac]-catalyzed mild preparation of 6-amino-4-aryl-5-cyano-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole derivatives

We report a new, one-pot, efficient, four-component condensation of hydrazine hydrate, ethyl acetoacetate, arylaldehydes, and malononitrile in the presence of a reusable weakly basic ionic liquid, 1,8-diazabicyclo[5.4.0]-undec-7-en-8-ium acetate, as catalyst, for synthesis of 6-amino-4-aryl-5-cyano-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole derivatives under solvent-free conditions at room temperature. The method has several advantages, for example good yields, short reaction times, and simple work-up procedure.     

Synthesis,characterization and application of Fe3O4@SiO2@CPTMO@DEA-SO3H nanoparticles supported on bentonite nanoclay as a magnetic catalyst for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles

Fe₃O₄ nanoparticles were prepared and decorated on the surface of nanobentonite (NB), and subsequently modified by the organic and inorganic linkers and then sulfonic acid immobilization on the nanoparticles. The NB-Fe₃O₄@SiO₂@CPTMO@DEA-SO₃H catalyst was characterized via Fourier transform-infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, vibrating-sample magnetometer, X-ray diffraction patterns, Brunauer–Emmett–Teller and thermal gravimetric analysis. The new catalyst benefits from a simple preparation method, and environmentally friendly and high magnetic properties of the nanocatalyst, Accordingly, we used it for the synthesis of dihydropyrano[2,3c]pyrazole derivatives in water and ethanol mixture as a green solvent under reflux conditions. Use of mild conditions, easy catalyst separation, cost-effectiveness, short reaction time, reusability of the catalyst, excellent yield and easy work-up are the main advantages of the present method.     

Efficient reactions for the synthesis of pyrazolo[3,4-b]pyridine and pyrano[2,3-c]pyrazole derivatives from N-methyl-1-(methylthio)-2-nitroethen-1-amine

The efficient and novel method for the synthesis of pyrazolo[3,4-b]pyridine and pyrano[2,3-c]pyrazole derivatives from the multicomponent reaction of aromatic aldehydes (isatins), N-methyl-1-(methylthio)-2-nitroethen-1-amine, and 3-aminopyrazole or methyl 3-hydroxy-1H-pyrazole-5-carboxylate under normal laboratory conditions was reported in this research. The advantages of this research are wide range of substrates, high yields, and simple operation.     

Diazo complexes of rhenium: preparations and crystal structures of the bis(dinitrogen), [Re(N2)2(PPh(OEt)2)4][BPh4] and methyldiazenido [ReCl(CH3N2)(CH3NHNH2)(PPh(OEt)2)3][BPh4] derivatives

Depending on experimental conditions and the nature of the hydrazine, the reactions of ReCl3P3 [P = PPh(OEt)2] with RNHNH2 (R = H, CH3, tBu) afford the bis(dinitrogen) [Re(N2)2P4]+ (2+), dinitrogen ReClN2P4 (3), and methyldiazenido [ReCl(CH3N2)(CH3NHNH2)P3]+ (1+) derivatives. In contrast, reactions of ReCl3P3 [P = PPh(OEt)2, PPh2OEt] with arylhydrazines ArNHNH2 (Ar = Ph, p-tolyl) give the aryldiazenido cations [ReCl(ArN2)(ArNHNH2)P3]+ (4+) and [ReCl(ArN2)P4]+ (7+) and the bis(aryldiazenido) cations [Re(ArN2)2P3]+ (5+, 6+). These complexes were characterized spectroscopically (IR; 1H and 31P NMR), and the BPh4 complexes 1, 2, and 7 were characterized crystallographically. The methyldiazenido derivative [ReCl(CH3N2)(CH3NHNH2)(PPh(OEt)2)3][BPh4] (1) crystallizes in space group P1 with a = 15.396(5) A, b = 16.986(5) A, c = 11.560(5) A, alpha = 93.96(5) degrees, beta = 93.99(5) degrees, gamma = 93.09(5) degrees, and Z = 2 and contains a singly bent CH3N2, group bonded to an octahedral central metal. One methylhydrazine ligand, one Cl- trans to the CH3N2, and three PPh(OEt)2 ligands complete the coordination. The complex [Re(N2)2(PPh(OEt)2)4][BPh4] (2) crystallizes in space group Pbaa with a = 23.008(5) A, b = 23.367(5) A, c = 12.863(3) A, and Z = 4. The structure displays octahedral coordination with two end-on N2 ligands in mutually trans positions. [ReCl(PhN2)(PPh(OEt)2)4][BPh4] (7) crystallizes in space group P2(1)/n with a = 19.613(5) A, b = 20.101(5) A, c = 19.918(5) A, beta = 115.12(2) degrees, and Z = 4. The structure shows a singly bent phenyldiazenido group trans to the Cl- ligand in an octahedral environment. The dinitrogen complex ReClN2P4 (3) reacts with CF3SO3CH3 to give the unstable methyldiazenido derivative [ReCl(CH3N2)P4][BPh4]. Reaction of the methylhydrazine complex [ReCl(CH3N2)(CH3NHNH2)P3][BPh4] (1) with Pb(OAc)4 at -30 degrees C results in selective oxidation of the hydrazine, affording the corresponding methyldiazene derivative [ReCl(CH3N=NH)(CH3N2)P3][BPh4] (8). In contrast, treatment with Pb(OAc)4 of the related arylhydrazines [ReCl(ArN2)(ArNHNH2)P3][BPh4] (4) [P = PPh(OEt)2] gives the bis(aryldiazenido) complexes [Re(ArN2)2P3][BPh4] (5). Possible protonation reactions of Br?nsted acids HX with all diazenides, 1, 4, 5, 6, and 8, were investigated and found to proceed only in the cases of the bis(aryldiazenido) complexes 5 and 6, affording, with HCl, the octahedral [ReCl(ArN=NH)(ArN2)P3][BPh4] or [ReCl(Ar(H)NN)(ArN2)P3][BPh4] (10) (Ar = Ph; P = PPh2OEt) derivative.     

Cesium carbonate supported on hydroxyapatite coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles as an effi cient and green catalyst for the synthesis of pyrano[2,3-c]pyrazoles

Cesium carbonate supported on hydroxyapatite coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (Ni0.5Zn0.5Fe2O4@Hap-Cs2CO3) was found to be magnetically separable, highly efficient, green and recyclable heterogeneous catalyst. The synthesized nanocatalyst has been characterized with several methods (FT-IR, SEM, TEM, XRD and XRF) and these analyzes confirmed which the cesium carbonate is well supported to catalyst surface. After full characterization, its catalytic activity was investigated in the synthesis of pyranopyrazole derivatives and the reactions were carried out at room temperature in 50:50 water/ethanol with excellent yields (88-95%). More importantly, the Ni0.5Zn0.5Fe2O4@Hap-Cs2CO3 was easily separated from the reaction mixture by external magnetic field and efficiently reused at least six runs without any loss of its catalytic activity. Thus, the developed nanomagnetic base catalyst is potentially useful for the green and economic production of organic compounds.     

Synthesis of tetrahydrothiopyrano[3,2-c]pyrazole derivatives from 3-thianones

The synthesis of bicyclic pyrazoles and pyrazolones in which the fused ring contains a sulfur atom in different oxidation states is reported.     

Syntheses and structural study of trinuclear iron acetates [Fe3O(CH3COO)6(H2O)3]Cl· 6H2O and [Fe3O(CH3COO)6(H2O)3] [FeCl4]· 2CH3COOH

The structure of two trinuclear iron acetates [Fe₃O(CH₃COO)₆(H₂O)₃]Cl· 6H₂O (I) and [Fe₃O(CH₃COO)₆(H_2O)₃][FeCl₄] · 2CH₃COOH (II) was determined by X-ray diffraction analysis. Crystals I and II are ionic and belong to the orthorhombic system with parameters a = 13.704(3), b = 23.332(5), c = 9.167(2) Å, R = 0.0355, space goup P2₁2₁2 for I and a = 10.145(4), b = 15.323(6), c = 22.999(8) Å, R = 0.0752, space group Pbc2₁ for II. The complex cation [Fe₃O(CH₃COO)₆(H₂O)₃]⁺ has a μ₃-O-bridged structure typical for trinuclear iron (III) compounds. As shown by Mössbauer spectroscopy, the iron(III) ions are in the high-spin state. In trinuclear cations, antiferromagnetic exchange interaction takes place between the Fe(III) ions with the exchange parameter J = -26.69 cm^?1 for II (Heisenberg-Dirac-Van Vleck model for D_3h, symmetry).     

Synthesis of pyrano[2,3‐c]pyrazole derivatives using Fe3O4@SiO2@piperidinium benzene‐1,3‐disulfonate (Fe3O4@SiO2 nanoparticle‐supported IL) as a novel,green and heterogeneous catalyst

A simple, green and efficient protocol for the one‐pot four‐component synthesis of pyrano[2,3‐c ]pyrazole derivatives produced from reaction between aryl aldehydes, ethyl acetoacetate, malononitrile and hydrazine hydrate in the presence of nano magnetic piperidinium benzene‐1,3‐disulfonate was synthesized in water at 60 °C. The Fe₃O₄@SiO₂ nanoparticle‐supported IL was designed and synthesized. The present process offers advantages such as clean reaction, short reaction time, good to excellent yield, easy purification and easy recoverable catalyst.     

Theophylline as a new and green catalyst for the one-pot synthesis of spiro[benzo[a]pyrano[2,3-c]phenazine] and benzo[a]pyrano[2,3-c]phenazine derivatives under solvent-free conditions

A green, convenient, high yielding and one-pot procedure for the synthesis of novel spiro[benzo[a]pyrano[2,3-c]phenazine] derivatives by domino multi-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamines, ninhydrine, and malononitrile in the presence of a catalytic amount of 1,3-dimethyl-7H-purine-2,6-dione (theophylline) as an expedient, eco-friendly and reusable solid base catalyst under thermal, microwave irradiation and solvent-free conditions. This procedure has also been applied successfully for the synthesis of benzo[a]pyrano[2,3-c]phenazines.     

Fe3O4-supported N-pyridin-4-amine-grafted graphene oxide as efficient and magnetically separable novel nanocatalyst for green synthesis of 4H-chromenes and dihydropyrano[2,3-c]pyrazole derivatives in water

Research on Chemical Intermediates - Fe3O4-magnetized N-pyridin-4-amine-functionalized graphene oxide [Fe3O4@GO-N-(pyridin-4-amine)] was readily prepared via a three-step procedure. The synthesized...