Zn[aminoacid]2 hybrid materials applied as heterogeneous catalysts in the synthesis of β-enaminones

Hybrid materials have seized attention from scientific community mainly as heterogenic catalysts in organic reactions on a large scale succeeding in some organic compounds with high yields. One of the most important classes of hybrid materials used for this purpose involves the complexation of Zn and aminoacids. Herein, we introduced Zn[Pro]₂ and Zn[Gly]₂ in the synthesis of several β-enaminones via solvent free protocol and using an ultrasound device.     

[Bmim]<Subscript>5</Subscript>[PNiW<Subscript>11</Subscript>O<Subscript>39</Subscript>]·3H<Subscript>2</Subscript>O an organic–inorganic hybrid as catalyst for one-pot pseudo-five-component synthesis of tetrazolyldiazepines

In this research, two heterogeneous organic–inorganic hybrid catalysts, [bmim]₃[PW₁₂O₄₀]·3H₂O and [bmim]₅[PNiW₁₁O₃₉]·3H₂O, have been prepared. The catalysts were fully characterized by several techniques such as elemental analyses, Fourier transform infrared spectroscopy, thermo-gravimetric analysis, scanning electron microscope and energy-dispersive X-ray analysis. Next, the hybrid catalysts have been used for the synthesis of functionalized diazepines containing tetrazole ring. Tetrazolyl-1H-spiro[benzo[b]cyclopenta[e][1,4] diazepines products were obtained in excellent yields and mild experimental conditions using [bmim]₅[PNiW₁₁O₃₉]·3H₂O as catalyst. This process was carried out via a one-pot, pseudo-five-component condensation reaction by means of a 1,2-diamine, isocyanide, TMSN3 and two molecules of a linear or cyclic ketone in methanol, at ambient temperature.     

Polymerization of 3‐ethynylthiophene with homogeneous and heterogeneous Rh catalysts

3‐Ethynylthiophene (3ETh) was polymerized with Rh(I) complexes: [Rh(cod)acac], [Rh(nbd)acac], [Rh(cod)Cl]₂, and [Rh(nbd)Cl]₂ (cod is η²:η²‐cycloocta‐1,5‐diene and nbd η²:η²‐norborna‐2,5‐diene), used as homogeneous catalysts and with the last two complexes anchored on mesoporous polybenzimidazole (PBI) beads: [Rh(cod)Cl]₂/PBI and [Rh(nbd)Cl]₂/PBI used as heterogeneous catalysts. All tested catalyst systems give high‐cis poly(3ETh). In situ NMR study of homogeneous polymerizations induced with [Rh(cod)acac] and [Rh(nbd)acac] complexes has revealed: (i) a transformation of acac ligands into free acetylacetone (Hacac) occurring since the early stage of polymerization, which suggests that this reaction is part of the initiation, (ii) that the initiation is rather slow in both of these polymerization systems, and (iii) a release of cod ligand from [Rh(cod)acac] complex but no release of nbd ligand from [Rh(nbd)acac] complex during the polymerization. The stability of diene ligand binding to Rh‐atom in [Rh(diene)acac] catalysts remarkably affects only the molecular weight but not the yield of poly(3ETh). The heterogeneous catalyst systems also provide high‐cis poly(3ETh), which is of very low contamination with catalyst residues since a leaching of anchored Rh complexes is negligible. The course of heterogeneous polymerizations is somewhat affected by limitations arising from the diffusion of monomer inside catalyst beads. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2776–2787, 2008     

Synthesis,crystal structures,DNA/bovine serum albumin binding,DNA cleavage and cytotoxicity of five mononuclear zinc(II) complexes

Five new mononuclear zinc(II) complexes containing ligands with extended planar phenanthroline moieties (dipyrido‐[3,2‐a:2′,3′‐c]phenazine (dppz) or dipyrido[3,2‐d:2′,3′‐f] quinoxaline (dpq)), namely [Zn(dppz)(acac)₂]⋅CH₃OH ( 1 ), [Zn(dppz)(dbm)(OAc)] ( 2 ), [Zn(dpq)(dbm) (OAc)] 1.5H₂O ( 3 ), [Zn(dpq)(tfnb)(OAc)] ( 4 ) and [Zn(dpq)(tfnb)₂] ( 5 ), where acac = acetylacetonate, tfnb = benzoyltrifluoroacetone and dbm = dibenzoylmethane, were synthesized and structurally characterized. The binding ability of complexes 1 – 5 with calf thymus DNA was investigated by spectroscopic titration methods and viscosity measurements. Results indicate that all complexes bind to calf thymus DNA via intercalative mode, and the DNA binding affinities of dppz complexes 1 and 2 are apparently stronger than those of dpq complexes 3 – 5 . DNA photocleavage experiments reveal that these complexes are efficient DNA cleaving agents and they are more active in UV‐A (365 nm) than in visible light. In particular, the in vitro cytotoxicity of the complexes for human cancer cell line A549 demonstrates that the five compounds have anticancer activity with low IC₅₀ values. Meanwhile, interaction of the complexes with bovine serum albumin investigated using UV–visible and fluorescence methods indicates that all complexes can quench the intrinsic fluorescence of bovine serum albumin in a static quenching process.     

Nano‐Zn[2‐boromophenylsalicylaldiminemethylpyranopyrazole]Cl2 as a novel nanostructured Schiff base complex and catalyst for the synthesis of pyrano[2,3‐d]pyrimidinedione derivatives

Nano‐Zn[2‐boromophenylsalicylaldiminemethylpyranopyrazole]Cl₂ (nano‐[Zn‐2BSMP]Cl₂) as a novel nanostructured Schiff base complex was prepared and characterized using several techniques. Nano‐[Zn‐2BSMP]Cl₂ was used as an effective catalyst for the preparation of some pyrano[2,3‐d]pyrimidinedione derivatives by the multicomponent reaction of malononitrile, aryl aldehydes and barbituric acid derivatives. The novelty and efficiency of nano‐[Zn‐2BSMP]Cl₂ as a catalyst, in comparison with some other reported catalysts, for this synthetic transformation are the main features of this work.     

Synthesis of one-pot pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl) methanone derivatives via a multi-component using Fe3O4@TiO2-SO3H as a recoverable magnetic catalyst under microwave irradiation

ABSTRACT

A new one-pot method for the synthesis four-component of pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl)methanone derivatives has been developed in the presence of nano Fe₃O₄@TiO₂-SO₃H catalysts (heterogeneous acid) under microwave conditions and in a solvent-free environment at 180?W. One of the benefits of using this catalyst was its re-use in subsequent stages of its reaction without much loss in its activity, which was carried out by an external magnet and recovered. The catalyst was synthesized and characterized by XRD, EDX, TEM, FESEM, TGA-DTA, BET, VSM and AFM. The productivity of the products obtained from this protocol (MAOS) is significantly high and the shorter reaction time in the synthesis process over the reflux method. These results showed advantages for synthesis, such as mild reaction conditions, no use of toxic catalysts in the laboratory, solvent-free environment, low energy consumption and Economically Affordable.     

Carbon Dioxide Capture and Utilization with Isomeric Forms of Bis(amino)-Tagged Zinc Bipyrazolate Metal–Organic Frameworks

Aiming at extending the tagged zinc bipyrazolate metal–organic frameworks (MOFs) family, the ligand 3,3’-diamino-4,4’-bipyrazole ( 3,3’-H₂L ) has been synthesized in good yield. The reaction with zinc(II) acetate hydrate led to the related MOF Zn(3,3’-L) . The compound is isostructural with its mono(amino) analogue Zn(BPZNH₂) and with Zn(3,5-L) , its isomeric parent built with 3,5-diamino-4,4’-bipyrazole. The textural analysis has unveiled its micro-/mesoporous nature, with a BET area of 463 m² g⁻¹. Its CO₂ adsorption capacity (17.4 wt. % CO₂ at p_CO2 = 1 bar and T = 298 K) and isosteric heat of adsorption (Q_st = 24.8 kJ mol⁻¹) are comparable to that of Zn(3,5-L) . Both Zn(3,3’-L) and Zn(3,5-L) have been tested as heterogeneous catalysts in the reaction of CO₂ with the epoxides epichlorohydrin and epibromohydrin to give the corresponding cyclic carbonates at T = 393 K and p_CO2 = 5 bar under solvent- and co-catalyst-free conditions. In general, the conversions recorded are higher than those found for Zn(BPZNH₂), proving that the insertion of an extra amino tag in the pores is beneficial for the epoxidation catalysis. The best catalytic match has been observed for the Zn(3,5-L) /epichlorohydrin couple, with 64 % conversion and a TOF of 5.3 mmol(carbonate) (mmol_Zn)⁻¹ h⁻¹. To gain better insights on the MOF-epoxide interaction, the crystal structure of the [epibromohydrin@ Zn(3,3’-L) ] adduct has been solved, confirming the existence of Br⋅⋅⋅(H)−N non-bonding interactions. To our knowledge, this study represents the first structural determination of a [epibromohydrin@MOF] adduct.     

Preparation of supported yttrium alkoxides as catalysts for the polymerization of lactones and oxirane

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring‐opening polymerization of oxirane and ?‐caprolactone. In the two methods, [tris(hexamethyldisilyl)‐amide]yttrium {Y[N(SiMe₃)₂]₃} is the metal alkoxide precursor. It is directly reacted with the silanol groups of the support, in the first method, and this is followed by alcoholysis of the unreacted amide groups. The flexibility of this method seems to be limited because the grafting density and the structure of the grafted Y alkoxide (less than one alkoxide by metal) are independent of the experimental conditions. In the second method, Y[N(SiMe₃)₂]₃ is first reacted with 1 or 2 equiv of alcohol with the formation of the mixed Y alkoxide/amide. The amide functions are used to attach Y to the support. This method is free from side reactions, quite reproducible, and well suited to support one type of active species (monoalkoxide or dialkoxide). Preliminary experiments with ?‐caprolactone polymerization have confirmed the activity of the supported Y alkoxide, whatever preparation method is used. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 569–578, 2003     

Towards a Practical Development of Light‐Driven Acceptorless Alkane Dehydrogenation

The efficient catalytic dehydrogenation of alkanes to olefins is one of the most investigated reactions in organic synthesis. In the coming years, an increased supply of shorter‐chain alkanes from natural and shale gas will offer new opportunities for inexpensive carbon feedstock through such dehydrogenation processes. Existing methods for alkane dehydrogenation using heterogeneous catalysts require harsh reaction conditions and have a lack of selectivity, whereas homogeneous catalysis methods result in significant waste generation. A strong need exists for atom‐efficient alkane dehydrogenations on a useful scale. Herein, we have developed improved acceptorless catalytic systems under optimal light transmittance conditions using trans‐[Rh(PMe₃)₂(CO)Cl] as the catalyst with different additives. Unprecedented catalyst turnover numbers are obtained for the dehydrogenation of cyclic and linear (from C₄) alkanes and liquid organic hydrogen carriers. These reactions proceed with unique conversion, thereby providing a basis for practical alkane dehydrogenations.     

H3PW12O40@nano‐ZnO: An efficient,recyclable, and eco‐friendly catalyst for the green synthesis of novel benzo[a]pyrimido[5′,4′:5,6]pyrano[2,3‐c]phenazines via sequential multicomponent reactions under microwave irradiation

A simple, efficient, single‐pot synthesis of novel heteroaryl‐substituted benzo[a]pyrimido[5′,4′:5,6]pyrano[2,3‐c]phenazines has been developed via initial Knoevenagel, subsequent Michael, and final heterocyclization reactions of 2‐hydroxynaphthalene‐1,4‐dione, o‐phenylenediamine, aromatic aldehydes, and barbituric acid in the presence of H₃PW₁₂O₄₀@nano‐ZnO as a recyclable heterogeneous catalyst in EtOH under microwave irradiation (MWI). This sequential green process with several advantages, such as operational simplicity, high yield, low cost, easy handling, eco‐friendliness and reusability of the catalyst, absence of any tedious work‐up or purification, and avoidance of hazardous or toxic reagents/catalysts/solvents, opens an effective and convenient way to pyrano‐functionalized benzophenazine systems, which are promising compounds for different biomedical applications.     

2,6-Diacetylpyridinesalicylaldazine complexes of bivalent metal ions

Summary 2,6-Diacetylpyridinesalicylaldazine (H₂daps) forms complexes [Ni(H₂daps)ClH₂O]Cl, [M(H₂daps)Cl₂H₂O] (M = Mn, Co, Cu or Zn) and [M(daps)(H₂O)₂] (M = Mn, Co, Ni, Cu or Zn) which have been characterized by elemental analyses, physicochemical methods, spectroscopy and X-ray powder diffraction.     

Role of preparation parameters of Cu–Zn mixed oxide catalyst in solvent free glycerol carbonylation with urea

Solvent-free carbonylation of glycerol with urea to glycerol carbonate (GC) was achieved over heterogeneous Cu–Zn mixed oxide catalyst. Cu–Zn catalysts with different ratios of Cu:Zn were prepared using co-precipitation (CP) and oxalate gel (OG) methods. As compared to CuO–ZnO(2:1) catalyst prepared by oxalate gel (OG) method, much higher conversion of glycerol and highest selectivity towards glycerol carbonate (GC) was achieved with CuO–ZnO_CP(2:1) catalyst. Physicochemical properties of prepared catalysts were investigated by using XRD, FT-IR, BET, TPD of CO₂ and NH₃ and TEM techniques. The effect of stoichiometric ratio of Cu/Zn, calcination temperature of CuO–ZnO catalysts and effect of reaction parameters such as molar ratio of substrates, time and temperature on glycerol conversion to GC were critically studied. Cu/Zn of 2:1 ratio, glycerol–urea 1:1 molar ratio, 145 ​°C reaction temperatures were found to be optimized reaction conditions to achieve highest glycerol conversion of 86% and complete selectivity towards GC. The continuous expel of NH₃ from reaction the mixture avoided formation of ammonia complex with CuO–ZnO catalyst. As a result of this, CuO–ZnO catalyst could be recycled up to three times without losing its initial activity.     

Microcrystalline Zinc Coordination Polymers as Single‐site Heterogeneous Catalysts for the Selective Synthesis of Mono‐oxazolines from Amino Alcohol and Dinitriles

In our effort to develop coordination polymers (CPs)‐based single‐site catalysts for the selective synthesis of mono‐oxazolines, two Zn‐based CPs, [{Zn₆(idbt)₄(phen)₄} ?3 H₂O]_n ( 1 ) and [{Zn₃(idbt)₂(H₂O)₄}?2 H₂O]_n ( 2 ) (H₃idbt= 5,5′‐(1H‐imidazole‐4,5‐diyl)‐bis‐(2H‐tetrazole), phen=1,10‐phenanthroline) have been synthesized. They exhibit two‐dimensional structure and contain isolated and accessible catalytically active sites, mimicking the site isolation of many catalytic enzymes. Micro CPs 1 and 2 are obtained by using surfactant‐mediated hydrothermal methods, and an investigation is conducted to explore how different surfactants affect their morphologies and particle sizes. Furthermore, micro 1 and 2 have shown to be effective heterogeneous catalysts for the reaction of amino alcohols and aromatic dinitriles, and exerted a significant influence on the selectivity of the catalytic reactions, yielding mono‐oxazolines as the major reaction product.     

Probing the Nature of Zinc in Copper-Zinc-Zirconium Catalysts by Operando Spectroscopies for CO2 Hydrogenation to Methanol

Active Zn species in Cu-based methanol synthesis catalysts have not been clearly identified yet due to their complex nature and dynamic structural changes during reactions. Herein, atomically dispersed Zn on ZrO₂ support is established in Cu-based catalysts by separating Zn and Zr components from Cu (Cu−ZnZr) via the double-nozzle flame spray pyrolysis (DFSP) method. It exhibits superiority in methanol selectivity and yield compared to those with Cu−ZnO interface and isolated ZnO nanoparticles. Operando X-ray absorption spectroscopy (XAS) reveals that the atomically dispersed Zn species are induced during the reaction due to the strengthened Zn−Zr interaction. They can suppress formate decomposition to CO and decrease the H₂ dissociation energy, shifting the reaction to methanol production. This work enlightens the rational design of unique Zn species by regulating coordination environments and offers a new perspective for exploring complex interactions in multi-component catalysts.     

Highly Stable Copper(I)–Thiacalix[4]arene-Based Frameworks for Highly Efficient Catalysis of Click Reactions in Water

Environmentally friendly metal–organic frameworks (MOFs) have gained considerable attention for their potential use as heterogeneous catalysts. Herein, two Cu^I-based MOFs, namely, [Cu₄Cl₄L] ⋅ CH₃OH ⋅ 1.5 H₂O ( 1-Cl ) and [Cu₄Br₄L] ⋅ DMF ⋅ 0.5 H₂O ( 1-Br ), were assembled with new functionalized thiacalix[4]arenes (L) and halogen anions X⁻ (X=Cl and Br) under solvothermal conditions. Remarkably, catalysts 1-Cl and 1-Br exhibit great stability in aqueous solutions over a wide pH range. Significantly, MOFs 1-Cl and 1-Br , as recycled heterogeneous catalysts, are capable of highly efficient catalysis for click reactions in water. The MOF structures, especially the exposed active Cu^I sites and 1D channels, play a key role in the improved catalytic activities. In particular, their catalytic activities in water are greatly superior to those in organic solvents or even in mixed solvents. This work proposes an attractive route for the design and self-assembly of environmentally friendly MOFs with high catalytic activity and reusability in water.     

Transesterification Reaction of Dimethyl Terephthalate by 2-Ethylhexanol in the Presence of Heterogeneous Catalysts under Solvent-free Condition

In this study, the synthesis of bis-（2-ethylhexyl） terephthalate, via the transesterification reaction of dimethyl terephthalate （DMT） by 2-ethylhexanol in the presence of different heterogeneous catalysts, such as Pb（OAc）2·3H2O, Cd（OAc）2·2H2O, Zn（OAc）2·2H2O, Hg（OAc）2·Ca（OAc）2·H2O, Cu（OAc）2·H2O, NaOAc, CaCO3, CaO, ZnSO4·7H2O, and sulfated zirconia, has been investigated. The reactivity of the catalysts in the reaction progress has been studied and compared. It was found that, hydrated cadmium acetate and sulfated zirconia were reactive catalysts to this reaction. The extent of transesterification of methyl ester groups reached up to 93% and 85.6% using these catalysts, respectively.     

Synthesis,crystal structure,and density functional theory study of a zinc(II) complex containing terpyridine and pyridine-2,6-dicarboxylic acid ligands: Analysis of the interactions with amoxicillin

An octahedral zinc(II) complex of 2,2′:6′,2″-terpyridine (Tpy) and pyridine-2,6-dicarboxylate (Pydc), [Zn(II)(Tpy)(Pydc)·4H₂O] was synthesized and its structure was determined by a single-crystal X-ray diffraction. The ligand pyridine-2,6-dicarboxylate coordinated to the zinc(II) ion via two pairs of carboxylate oxygens and one nitrogen atom, whereas 2,2′:6′,2″-terpyridine also contributed three coordination bonds through its nitrogen atoms. [Zn(II)(Tpy)(Pydc)·4H₂O] showed luminescence properties between 412 and 435 nm in DMSO. The solid-state octahedral geometry of [Zn(II)(Tpy)(Pydc)·4H₂O] was also preserved in solution as confirmed by the observed UV λ_ex = 346. Experimental and theoretical studies indicated that [Zn(II)(Tpy)(Pydc)·4H₂O] interacted with amoxicillin. Density functional theory calculations at B3LYP/LanL2dz level of theory suggested that [Zn(II)(Tpy)(pydc)·4H₂O] dimer interacts with (2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid (amoxicillin) via highest occupied molecular orbital and lowest unoccupied molecular orbital, π–π interaction, hydrogen bond interaction, and van der Waals forces, thus influencing [Zn(II)(Tpy)(Pydc)·4H₂O] properties.     

A new ligand system containing sulfanilamide and quinazolinone fragments: Synthesis,structure, and properties

A new Schiff base ligand, 4-methyl-N-{2-[(2-methyl-4-oxo-3,4-dihydroquinazolin-3-yl)iminomethyl]-phenyl}benzenesulfonamide (L), and its complexes with transition metals [Cd(L)₂], [Zn(L)₂], and [CuLOAc] have been synthesized. The structure and electronic properties of the ligand have been studied by quantum chemical methods, and its zinc and cadmium complexes have been found to exhibit luminescence properties.     

乙酸功能化离子液体作为高效、可回收的催化剂用于2-萘酚与芳醛缩合反应(英文)

An efficient solvent‐free protocol for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes from the condensation of 2‐naphthol with arylaldehydes, using acetic acid functionalized imidazolium salts (1‐carboxymethyl‐3‐methylimidazolium bromide ([cmmim]Br) and 1‐carboxymethy1‐3-me-thylimidazolium tetrafluoroborate([cmmim]BF4) as reusable catalysts, has been developed. The turn over frequency on the catalysts is several times higher than the other previously reported catalysts. Also, thermal gravimetric analysis and powder X‐ray diffraction pattern of the catalysts have been studied.     

Free radicals formed by ion beam neutralization of [DCO]+, [DOCO] +, [CD3OD2]+ and [(CD3)2COD] + on metal targets

A series of radicals formed when a fast beam of deuterated ions, [DCO] ⁺, [DOCO] ⁺, [CD₃OD₂]⁺ and [(CD) ₂COD] ⁺, is neutralized by electron transfer from K. Na and Zn atoms has been studied by a combination of charge stripping and beam scattering techniques For all systems studied, some fraction of The radicals from charge exchange are formed in excited dissociative states. Radical decomposition products have been identified and fragmentation energies have been measured. A metastable slate of CD3GD2 is observed with a lifetime greater than 0.5 μs. Stable radicals of DCO and (CD₃)₂ COD are formed by ion–Zn charge exchange. Indirect evidence indicates that [DCO] ⁺–K charge exchang; leads to an excited radiative state of the radical.