Designing of a magnetically separable Fe3O4@dopa@ML nano-catalyst for multiple organic transformations (epoxidation,reduction, and coupling) in aqueous medium

A copper(II) macrocyclic Schiff base complex (ML) was synthesized by condensation between 2,2-dimethylpropane-1,3-diammine and 2,6-diformyl-4-butylphenol with the aim to modify the surface of widely used magnetically separable nanocatalyst Fe₃O₄@dopa. ML was characterized by physicochemical techniques and single crystal X-ray diffraction. The newly synthesized heterogeneous catalyst Fe₃O₄@dopa@ML was characterized by SEM, TEM, PXRD, EDX, TGA, etc. ML showed stability in aqueous medium and utilizing this unique property, the heterogeneous catalyst Fe₃O₄@dopa@ML was used for catalyzing epoxidation, nitroarene reduction and C–C coupling (Henry reaction) in aqueous medium. The separation method of the prepared nano-catalyst is very easy and can be done with an external magnetic field. The experimental findings suggest that Fe₃O₄@dopa@ML is a versatile “green catalyst.”     

Silica supported orthophosphoric acid (H3PO4. SiO2): a green,heterogeneous catalyst for solvent-free oxathioacetalization of aldehydes

Abstract

A silica supported orthophosphoric acid catalyst (H₃PO₄. SiO₂) was prepared by stirring silica gel (100–200mesh) with orthophosphoric acid in chloroform at room temperature. The catalyst was characterized by scanning electron microscopy (SEM) and energy dispersion analytical X-ray (EDX). It demonstrated excellent activity, chemoselectivity, and recyclability for oxathioacetalization of aldehydes.     

Synthesis of 2, 5, 5-Trimethylhepta-2, 6-Dien-4-One (Artemisia Ketone): II. Using A Thioacetal Monoxide

The polymer-bound catalyst 3a-e inserted some spacer ([-NHCO(CH_{2 10- n}; n = 0,1,2,3,4) connecting the catalytic moiety [cyclo(-(S)-Phe-(S)-His)], [(S,S)-1] and 2% cross-linked Merrifield's polymer, have been prepared and their catalytic efficiency for the enantioselective hydrocyanation of 3-phenoxybenzaldehyde was studied.     

Synthesis of an electro-catalyst based on a cobalt(II) complex with dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methylphenol)

A catalyst based on [LCo(H₂O)] (1) is formed by the reaction of dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methyl)phenol (H₂L) with CoBr₂ for electrolytic proton or water reduction. 1 catalyzes hydrogen evolution, both from acetic acid with a turnover frequency (TOF) of 17.9 mol of hydrogen per mole of catalyst per hour at an overpotential of 792 mV (in DMF) and from water with a TOF of 260 mol of hydrogen per mole of catalyst per hour at an overpotential of 889 mV (in buffer, pH 7.0).     

Synthesis,characterization, crystal structure,catalytic activity in oxidative bromination,and thermal study of a new oxidovanadium Schiff base complex containing O,N-bidentate Schiff base ligand

A new oxidovanadium(IV) Schiff base complex, VOL₂ (1), HL = 2-{(E)-[2- (bromoethyl)imino]methyl}-6-methoxy phenol, containing ethyl bromide pendant group was synthesized by direct reaction of HL and VO(acac)₂ in the ratio of 2 : 1 in methanol at reflux. The Schiff base ligand and its vanadyl complex were characterized by FT-IR spectra and CHN analysis. Additionally, the Schiff base ligand has been characterized by ¹H NMR spectroscopy. The crystal structure of 1 was also determined by single-crystal X-ray analysis, showing the distorted square-pyramidal N₂O₃ coordination around vanadium(IV). The catalytic activity of 1 was studied in the oxidative bromination of 2-nitrophenol as a model substrate, and different reaction parameters were investigated. The oxidative bromination of some organic compounds in the presence of 1 in optimal conditions showed that it was an effective and selective catalyst in those optimal conditions. Thermogravimetric analysis of 1 showed that it decomposed in two stages. 1 was thermally decomposed in air at 660 °C, and the XRD pattern of the obtained solid showed the formation of the V₂O₅ nanoparticles with average size of 34 nm .     

Synthesis,characterization, and catalysis of recyclable new piperazine-bridged Mo(VI) polymers [MoO2(Salen)(piperazine)]n in highly selective oxygenation of alkenes and sulfides

This study reports synthesis and characterization of polymeric [MoO₂(Salen)] complexes that combine MoO₂(acac)₂ and polymeric ligands bearing N₂O₂ coordination sites, abbreviated herein as [piperazinCH₂{MoO₂(Salen)}]_n (6), [piperazinCH₂{MoO₂(Salophen)}]_n (7), and [piperazinCH₂{MoO₂(Salpn)}]_n (8). The epoxidation of alkenes using tert-butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were enhanced with excellent selectivity under the catalytic influence of these coordination polymers. No relevant difference in activity was found due to change in the diamine in the Schiff’s base ligands. The stability of polymeric catalysts was assessed by recycling a sample five times in small batch reactions in both epoxidation and sulfoxidation. In the case of cyclooctene epoxidation, catalytic activity of [piperazinCH₂{MoO₂(Salen)}]_n increased without losing the selectivity, whereas the catalytic activity and selectivity of the spent catalyst decreased in sulfoxidation of methyl phenyl sulfide in consecutive runs. Loss of Mo from the coordination polymer has been investigated using the filtrates as potential catalysts in sulfoxidation reactions. Molybdenum leaching degree decreases through five cycles. Moreover, the catalyst can be recovered from the reaction mixture unchanged as determined by IR and UV–Vis spectra.     

Synthesis,crystal structure and catalytic activity of an oxo-diperoxo tungsten(VI) complex containing an oxazine ligand for selective oxidation of sulfides

Abstract

A novel oxo-diperoxo tungsten(VI) complex, [WO(O₂)₂(Hphox)], was prepared by reaction of WO₃ in H₂O₂ with an oxazine-type ligand, 2-(2′-hydroxylphenyl)oxazine (Hphox). The complex was characterized by FTIR, ¹H NMR and elemental analysis. The single-crystal X-ray diffraction studies revealed a seven-coordinate tungsten center with a distorted octahedral geometry. The [WO(O₂)₂(Hphox)] complex was applied as a catalyst in efficient and selective oxidation of sulfide to sulfoxide using 30% H₂O₂ or UHP (urea hydrogen peroxide) as oxidants. This catalyst showed excellent catalytic activities and high selectivities in producing a variety of aryl and alkyl sulfoxides under mild conditions. To get an insight into the mechanisms of oxidation of sulfides, the mechanistic studies were monitored by UV–Vis spectroscopy.     

Synthesis,characterization, and reactivity studies in ethylene polymerization of cyclometalated palladium(II) complexes containing terdentate ligands with N,C,N-donors

The reaction of [Na₂PdCl₄] with 3,5-bis(2-pyridoxy)toluene (L_pyH) in acetic acid yields the cyclometalated complex [PdCl(L_py-N, C, N)] (1). Complex 1 can be further converted into neutral species by metathesis reaction exchange of chloride by either iodide or thiocyanate to yield [PdX(L_py-N, C, N)] (X = I (2), SCN (3)). The chloride can be replaced by neutral ligands like pyridine or acetonitrile in the presence of silver tetrafluoroborate to give the corresponding cationic compounds [PdL(L_py-N, C, N)]BF₄ (L = Py (4), MeCN (5)). In contrast, the reaction of [Na₂PdCl₄] with 3,5-bis(3, 5-dimethylpyrazol-1-ylmethyl)toluene (L_pzH) under analogous conditions yields the neutral complex [PdCl₂(L_pzH-N, N)](6) with the ligand bidentate N,N-donor. The cyclometalated palladium complex [PdCl(L_pz-N, C, N)] (7) was prepared by the reaction of Pd(OAc)₂ with L_pzH in acetic acid followed by a metathetic reaction with lithium chloride in acetone/water. Complexes 1, 6, and 7 in the presence of methylaluminoxane (MAO) lead to an active catalyst for the polymerization of ethylene.     

Modification of polymethylhydrosiloxane by dehydrocoupling reactions catalyzed by transition metal complexes: Evidence for the preservation of linear siloxane structures

Polysiloxanes with pendant poly(ethylene oxide) side chains (4 were prepared by the dehydrocoupling reaction of poly(methylhydrosiloxane) (PMHS, 3 with 2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethoxy)ethanol (1 and poly(ethylene glycol) methyl ether (2 using a metal catalyst. Catalysts investigated were tin(II) 2-ethylhexanoate, Rh(Ph₃P)₃Cl, and Pd₂(dba)₃. The reaction of a cyclic siloxane, D₄^H, with 1 catalyzed by Pd₂(dba)₃ was also carried out to synthesize siloxane 6. The polysiloxanes were characterized by ¹H NMR, ²⁹Si NMR, FT-IR, and GPC. ²⁹Si NMR study of these comb-like polysiloxanes revealed that there is a significant difference in the structure of the siloxane polymers prepared depending upon the catalyst. M, D, and T units were observed when tin(II) was used as a catalyst, but only M and D units were detected when Rh(Ph₃P)₃Cl or Pd₂(dba)₃ was employed. Furthermore, M and T units are negligible for the cyclic siloxane 3 using Pd₂(dba)₃. A mechanism is proposed to account for these observations.     

Addition of H2-D2 Mixtures to 2-Butyne and Norbornene Catalyzed by Solutions of Chlorotris(triphenylphosphine)rhodium(I), Hydridocarbonyltris(triphenylphosphine)rhodium(I), and Hydridotetrakis(5-phenyl-5-H-dibenzophosphole)rhodium(I)

The use of H₂/D₂ mixtures in place of H₂ as a probe of the mechanisms of hydrogenation is explored using the catalyst precursors chlorotris(triphenylphosphine)rhodium(I) (I), hydridocarbonyltris(triphenylphosphine) rhodium(I) (II), and hydridotetrakis(5-phenyl-5-H-dibenzophosphole)rhodium (I) (III). Benzene solutions of these complexes catalyze the H₂-D₂ equilibration, the relative rates decreasing in the order III > II > I. The accepted mechanism of hydrogenation catalyzed by I does not accommodate the observed isotopic exchange, which is inhibited by added acids (trifluoroethanol, 1,3,4-trichlorophenol) and accelerated by small amounts of triethylamine; the formation of hydridotris(triphenylphosphine)rhodium(I) is implicated. The H₂ and D₂ added to an unsaturated hydrocarbon is randomized with complexes II and III as the catalyst, whereas the molecular identity of H₂ and D₂ is retained if the dihydrido is the catalyst. __________ From Kinetika i Kataliz, Vol. 46, No. 6, 2005, pp. 891–900. Original English Text Copyright ? 2005 by Lin, Siegel. This article was submitted by the authors in English. The experiments were conducted at the University of Arkansas.     

Synthesis,characterization of SiO2 supported-industrial phosphoric acid catalyst for hydrolysis of NaBH4 solution

Abstract

Tunisian industrial phosphoric acid H₃PO₄ was supported on silica gel SiO₂ (SIPA) to catalyze the hydrolysis reaction of aqueous alkaline sodium borohydride (NaBH₄). The SiO₂ was produced from purified quartz sand using alkali fusion-acidification chemical process. The BET surface area results indicate that the prepared silica gel could reach a specific surface area up to 585 m²/g. The addition of PO₃H₂ functional groups resulted in an increase of surface acidity of SiO₂ catalyst as shown by FT-IR and DTA-DTG spectra. The total acidity of SIPA catalyst was determined by titration to be 2.8?mmol H⁺/g. SEM/EDS maps reveal the distribution of heavy metals on the silica surface. The effect of supported PO₃H₂ functional groups and heavy metals on the NaBH₄ hydrolysis reaction was studied for different ratios of SIPA catalyst to NaBH₄. The sample 12SIPA/NaBH₄ leads to a very high hydrogen generation rate (up to 90%). The activation energy of hydrogen generation by NaBH₄ hydrolysis was 25.7?kJ mol^?1.     

NH4H2PO4/SiO2: a recyclable,efficient heterogeneous catalyst for crossed aldol condensation reaction

Abstract

Crossed aldol condensation of aromatic aldehydes with cyclic ketones in the presence of catalytic amount of NH₄H₂PO₄/SiO₂ (as a safe, green, and cheap heterogeneous catalyst) under solvent-free condition afforded α,?-bis(substituted-benzylidene) cycloalkanones in high yields. This method is general with respect to all types of aromatic aldehydes and is an eco-friendly procedure. And the catalyst is easily prepared, stable, reusable, and efficient under the reaction conditions.     

Novel cobalt nitride-induced oxygen activation on Pt-based catalyst for catalytic oxidation

Abstract

Cobalt nitride as a new type of O₂ activator was used to modify Pt-based catalyst for catalytic oxidation. The nitrided Co/Pt/γ-Al₂O₃ catalyst system was highly efficient for preferential CO oxidation in excess H₂ at low temperatures, which was attributed to a noncompetitive dual-site reaction pathway.     

磺酸基功能化有机聚苯乙烯/无机磷酸氢锆催化环氧大豆油

首先制备了2种磺酸功能化的有机聚苯乙烯/无机磷酸氢锆非均相催化剂,运用傅里叶红外光谱(FT-IR)、N2吸附-脱附测试、X射线衍射(XRD)、扫描电子显微镜(SEM)等测试技术对催化剂进行了表征,提出了催化剂可能的模型。其次,考察了非均相催化剂催化合成环氧化大豆油的催化性能。结果表明:以叔丁基过氧化氢(TBHP)为氧化剂,固体催化剂对大豆油的环氧反应具有良好的催化性能,相比于催化剂1(磺酸化低聚苯乙烯基膦酸-磷酸氢锆),在相同的条件下,催化剂2(磺酸化聚(苯乙烯-苯乙烯膦酸)-磷酸氢锆)表现出更高的催化活性(产率:58.6%vs 53.3%),这主要归因于催化剂2拥有更大的比表面积、孔容以及孔径,为底物和催化剂的接触提供足够的催化场所。催化剂2重复使用7次后,催化活性未见明显降低。第8次反应结束后,将其置于2 mol·L-1稀盐酸中静置过夜后,在进行第9和10次循环时,催化活性又得以恢复。     

One-Pot,Facile, Highly Efficient,and Green Synthesis of Acridinedione Derivatives Using Vitamin B1

An efficient methodology for the synthesis of acridinedione derivatives 4a–o has been achieved by one-pot, multicomponent condensation of dimedone 1, various amines 2a–d, and substitute aromatic aldehydes 3a–k, in the presence of the easily available, inexpensive, and nontoxic catalyst vitamin B₁ (VB₁) as a versatile biodegradable. Synthesis of acridine-type compounds was performed in good yields in water as green solvent. Its high-yield efficiency; clean, ecofriendly, simple workup procedure; and easy purification are regarded as the main advantages of this method besides its green solvent. The synthesized compounds are characterized using spectroscopic analyses (FTIR, ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry) techniques.     

Synthesis,structure and olefin polymerization catalysis of nickel(II) complexes bearing N,O-chelate ligands

Four β-ketoimine ligands (two series) were prepared through traditional condensation reactions of β-diketones with 2,6-substituted anilines. Reaction took place only at the cyclohexanone carbonyl rather than at the acetyl or benzoyl carbonyl, even if more than two equivalents of the amines were added. Consequently, four new moisture- and air-stable bis(β-ketoamino)nickel(II) complexes, Ni[2–CH₃C(O)C₆H₈(=NAr)]₂ (Ar?=?2, 6-iPr₂C₆H₃, (1); Ar?=?2, 6-Me₂C₆H₃, (2) and Ni[2–PhC(O)C₆H₈(=NAr)]₂ (Ar?=?2, 6-iPr₂C₆H₃, (3); Ar?=?2, 6-Me₂C₆H₃, (4) were obtained and characterized. The solid-state structures of complex 1, 2 and 3 have been determined by single-crystal X-ray diffraction. Additionally, these complexes can be applied as highly active catalyst precursors for vinyl polymerization of norbornene (NBE) after activation with methylaluminoxane (MAO).     

Ultrasound-promoted green approach for the synthesis of multisubstituted pyridines using stable and reusable SBA-15@ADMPT/H5PW10V2O40 nanocatalyst at room temperature

ABSTRACT

A facile one-pot protocol for the synthesis of 2-amino-3-cyanopyridins using SBA-15@Triazine/H₅PW₁₀V₂O₄₀ as an efficient catalyst under ultrasonic conditions has been developed. The nanohybrid catalyst was prepared by the chemical anchoring of Keggin heteropolyacid H₅PW₁₀V₂O₄₀ onto the surface of SBA-15 mesoporous silica modified with 2-APTS -4,6-bis(3,5-dimethyl-1H-pyrazol- 1-yl)-1,3,5-triazine (ADMPT) linker. Then the nanohybrid was used as a green, efficient, eco-friendly, and highly recyclable catalyst for the one-pot and multi-component synthesis of 2-amino-3-cyanopyridin derivatives from the reaction of aldehydes, malononitrile, cyclic ketones and ammonium acetate under ultrasound waves with good to excellent yields (79–95%) and in a short span of time. This nanocatalyst was characterized by using FT-IR, XRD, SEM, TEM, BET, and EDX techniques.     

Efficient and versatile catalysis for β-alkylation of secondary alcohols through hydrogen auto transfer process with newly designed ruthenium(II) complexes containing ON donor aldazine ligands

A new series of ruthenium(II) carbonyl complexes, [RuCl(CO)(EPh₃)₂(L_1-2)] (1–4) (E = P or As; H₂L₁ = salicylaldazine, H₂L₂ = 2-hydroxynaphthaldazine), have been assembled from ruthenium(II) precursors [RuHCl(CO)(EPh₃)₃] and bidentate ON donor Schiff base ligands (H₂L_1-2). Both ligands and their new ruthenium(II) complexes have been characterized by elemental analyses, spectroscopic methods (UV, IR, NMR (¹H, ¹³C, ³¹P) as well as ESI mass spectrometry. The molecular structures of H₂L₁ and 1 have been confirmed by single crystal X-ray diffraction. Based on the above studies, an octahedral coordination geometry around the metal center has been proposed for 1–4. To investigate the catalytic effectiveness of 1–4, the complexes have been used as catalysts in β-alkylation of secondary alcohols with primary alcohols and synthesis of quinolines. The effect of solvent, time, base, catalyst loading, and substituent of the ligand moiety on the reaction was studied. Notably, 1 was a more efficient catalyst toward alkylation of a wide range of alcohols and quinolines synthesis. The reusability of the catalyst was checked and the results showed up to six catalytic runs without significant loss of activity.     

Novel Catalytic Acetylation of Alcohols with Preyssler's Anion, [NaP5Wa30O110]14– 1

Sodium 30-tungstopentaphosphate, the so-called Preyssler's anion with a formula of [NaP₅W₃₀O₁₁₀]^14– (I) catalyzes the acetylation of alcohols (C _n H_{2n + 1}OH, n = 2, 3, 4, 5) with acetic acid. High yield is obtained with I as pure acid or supported on silica. Both homogeneous and heterogeneous catalysts are discussed and compared. H₁₄[NaP₅W₃₀O₁₁₀], abbreviated as H₁₄-P₅, under homogeneous conditions, as well as supported on silica (heterogeneous conditions) is found to be an excellent catalyst. Our data indicate that, when the ammonium salt of I is employed as the catalyst, the yield increases as the alcohol carbon-chain is increased. This behavior is found to be quite general. The catalysts can be easily recovered and recycled with retention of their initial structure and activity.     

Eco-friendly development: synthesis of 3-(2-chloroquinolin-3-yl)-1-aryl prop-2-en-1-one using K2CO3–Al2O3 under ultrasonic radiations

Abstract

K₂CO₃–Al₂O₃ has been used as an efficient, eco-friendly, and cost-effective activating catalyst for the synthesis of 3-(2-chloroquinolin-3-yl)-1-substituted phenyl prop-2-en-1-ones starting from 2-chloroquinoline-3-carbaldehyde and acetophenone. The reactions were performed under ultrasound irradiations. A substantial enhancing effect in the yield was observed when the catalyst was activated under ultrasonic waves. The K₂CO₃–Al₂O₃ catalyst can compete with the traditional NaOH/MeOH system of catalysis when the reaction is carried out under ultrasound. Herein, a benign, eco-friendly, efficient, and extremely fast procedure for the synthesis of quinoline chalcones has been demonstrated successfully.