Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Using Ce(SO4)2-SiO2 as a Heterogeneous and Recyclable Catalyst

A simple and efficient synthesis of 3,4-dihydropyrimidinones or thiones is described, using silica-supported ceric sulfate [Ce(SO₄)₂-SiO₂] as a heterogeneous catalyst from an aldehyde, 1,3-dicarbonyl compound, and urea or thiourea at 110 °C under solvent-free conditions. Compared with the classical Biginelli reaction, this new method consistently has better yields, short reaction time, easy separation, and tolerance toward various functional groups.     

Regioselective Ring Opening of Styrene Oxide Catalyzed by MoO2(acac)2

The ring-opening reaction of styrene oxide with various nitrogen, oxygen, and carbon nucleophiles catalyzed by MoO₂(acac)₂ was described. The corresponding ring-opening compounds with nearly 100% regioselectivities were obtained under mild conditions in moderate to good yields. MoO₂(acac)₂ is a highly efficient catalyst for the ring opening of styrene oxide. The reaction serves as a simple and efficient method for the synthesis of 1,2-bifunctional compounds.     

An Efficient Synthesis of New 3,4-Dihydropyrimidin- 2(1H)-ones Incorporating a Phenyl Moiety at C-5 and C-6 Catalyzed by TMSCl and Co(OAc)2.4H2O

New 3,4-dihydropyrimidin-2-ones having a phenyl moiety at C-5 and C-6 have been prepared by a microwave-assisted Biginelli–like reaction by a three-component, one-pot condensation of an aromatic aldehyde, deoxybenzoin and urea, or thiourea using TMSCl and Co(OAc) ₂ .4H ₂ O as an efficient Lewis acid catalyst.     

Synthesis of 2,3-Dihydroquinazoline-4(1H)-ones

An efficient, inexpensive, and heterogeneous catalyst, [Al(H₂PO₄)₃], was applied in a three-component, one-pot cyclocondensation reaction of isatoic anhydride with primary amines (or ammonium salts) and aldehydes to afford the corresponding quinazolinone derivatives in excellent yields. Reactions occurred under thermal solvent-free conditions. It was found that this solid acidic catalyst could be easily recovered and reused for at least three cycles without any loss of activity.     

An Efficient Procedure for the Synthesis of Benzoxazole and Benzothiazole Derivatives Using a H2O2/SiO2-FeCl3 System

A series of benzoxazole and benzothiazoles was readily prepared from the reaction of ortho-aminophenol/ortho-aminothiophenol and aldehydes using solid silica supported ferric chloride (SiO₂-FeCl₃) as catalyst followed by oxidation with H₂O₂ under ambient conditions. Some of advantages of this method are a simple and convenient procedure, easy purification, and shorter reaction times.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Study on the Phenolic Oxidation by H2O2 Using Metallomicelles Composed of Dinuclear Copper(II) Complex as Synthetic Peroxidases

A dinuclear copper(II) complex [Cu₂(oxheel)] was synthesized and its structure was analyzed. This compound was then mixed with a surfactant (Brij35 or LSS) to form a metallomicelle, which would catalyze the phenol oxidation with the hydrogen peroxide (H₂O₂). The reaction mechanism and the mathematic model for the kinetics of this reaction were proposed, and the effect of the molar ratio between H₂O₂ and catalyst, of the temperature and of the pH levels on the rate of catalytic reaction were studied.     

Facile one-pot synthesis of 2-arylbenzothiazoles catalyzed by H3PO4/TiO2-ZrO2 (1/1) under solvent-free conditions

A highly efficient and simple protocol for the preparation of 2-arylbenzothiazoles through condensation of 2-aminothiophenol and different aldehydes in the presence of H₃PO₄/TiO₂-ZrO₂(1/1)-cetyl pyridinium bromide (CPB) is described. The reaction proceeded under mild and solvent-free conditions to afford 2-arylbenzothiazole derivatives. In this method, the title compounds were obtained in good to excellent yields and short reaction times. The structures of synthesized products were identified by infrared, ¹H NMR, ¹³C NMR, and mass spectroscopy.     

H6P2W18O62·14H2O as an efficient catalyst for the green synthesis of α-aminophosphonates from α-amino acids

Abstract

A simple, efficient and eco-friendly protocol has been described for the synthesis of α-aminophosphonates via Kabachnik-Fields reaction, catalyzed by H₆P₂W₁₈O₆₂·14H₂O as a reusable catalyst. The reaction was realized by condensation of amino acids, various aromatic aldehydes and triethylphosphite under solvent-free conditions, the corresponding α-aminophosphonates were formed in good yields. All the new products were characterized by IR, ¹H, ¹³C and ³¹P-NMR analyses. This method offers advantages such as simplicity workup with the green aspects, good yields and short reaction times.     

H2SO4-SiO2: Highly Efficient and Reusable Catalyst for per-O-Acetylation of Carbohydrates Under Solvent-Free Conditions

Sulfuric acid immobilized on silica gel (H₂SO₄-SiO₂) was used as an efficient promoter for per-O-acetylation of carbohydrates with acetic anhydride under solvent-free conditions. The substrates include not only monosaccharides and disaccharides, but also glycosides. The catalyst is recyclable and stable at room temperature, and the reaction protocol is simple, is cost-effective, and gives good isolated yield with high purity. The large-scale reactions also proceeded conveniently and in high yields.     

An efficient synthesis of 5-substituted 1H-tetrazoles via B(C6F5)3 catalyzed [3+2] cycloaddition of nitriles and sodium azide

A simple and efficient protocol is developed for the synthesis of 5-substituted 1H-tetrazole derivatives from various nitriles and sodium azide (NaN₃) via [3+2] cycloaddition reaction using B(C₆F₅)₃ as a catalyst. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, low toxicity, easy work-up, high yields, and compatibility with other functional groups.     

Reductive carbonylation of aryl and heteroaryl iodides using Pd(acac)2/dppm as an efficient catalyst

Palladium catalyzed simple and efficient protocol for reductive carbonylation of aryl and heteroaryl compounds has been developed. The formylation of aryl and heteroaryl iodides takes place in the presence of Pd(acac)₂/dppm catalyst at 10 bar pressure of synthetic gas to give the desired aromatic and heteroaromatic aldehydes in good to excellent yields. Easy work-up, stability of the catalyst, low catalyst loading and less reaction time are the advantages of this method.     

Preparation of ethyl levulinate from wheat stalk over Zr(SO4)2/SiO2

A series of Zr(SO₄)₂/SiO₂ solid acid catalysts with different Zr(SO₄)₂ loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N₂, and temperature-programmed desorption of NH₃. The results showed that the active component Zr(SO₄)₂ was successfully adhered to the mesoporous SiO₂, and the acid amount of Zr(SO₄)₂/SiO₂ increased with the increasing of the Zr(SO₄)₂ loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO₄)₂/SiO₂ to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO₄)₂/SiO₂ exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO₄)₂ loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation.     

Interaction Between Two Similar Plane Parallel Double Layers for (NH4)2Fe(SO4)2 or (NH4)2Cu(SO4)2 Type Complex Salt Electrolytes at Positive Surface Potential

Interaction energies between two similar plane parallel double layers for (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y _e  < y ₀ ≤ 20. The general expressions were given for the interaction energies of A _ν +B _ν′ +C_ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl₂, Na₂SO₄, FeCl₃, Na₃PO₄, Mg₃(PO₄)₂, Al₂(SO₄)₃, and complex salts (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ at y ₀ = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH₄)₂Fe(SO₄)₂ was close to that for simple salt Na₃PO₄.

Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

Hf(OTf)4-Catalyzed Three-Component Synthesis of N-Carbamate-Protected β-Amino Ketones

Hafnium(IV) triflate (Hf(OTf)₄) has been identified as a potent catalyst for the direct three-component synthesis of β-carbamate ketones. This new method, featuring a low catalyst loading, fast reaction rate, and solvent-free conditions, provided facile access to a diversity of carbamate-protected Mannich bases. A mechanistic investigation indicated that the three-component reaction proceeds via sequential aldol condensation and aza-Michael addition, but not the Mannich-type pathway.     

Pt/MOx(M=Ni,Fe,Co,Ce)催化剂上CO氧化反应中抗H2O与CO2的性能研究

我们研究了4种负载型Pt催化剂（1Pt/NiO、1Pt/FeO_x、1Pt/Co₃O₄和Pt/CeO₂）上不同反应条件下CO氧化活性及抗H₂O和CO₂性能.发现反应气氛中CO₂的加入与CO形成了竞争吸附,并在催化剂表面形成了碳酸盐物种堵塞了活性位,从而导致催化剂失活.反应气氛中H₂O的加入对1Pt/CeO₂催化剂的活性有所抑制,但对1Pt/FeO_x、1Pt/NiO和1Pt/Co₃O₄催化剂的活性却有促进作用.在1Pt/FeO_x和1Pt/CeO₂催化剂上的分步反应实验和动力学研究表明,尽管H₂O的加入在两种催化剂上均与CO形成了竞争吸附,但在1Pt/FeO_x催化剂上H₂O在载体表面解离形成的羟基更易与CO反应,开辟了新的反应途径,从而提高了反应性能.此外,H₂O的加入能有效分解该催化剂上的碳酸盐物种,从而保持了其稳定性.     

Etude de la deshydratation de Ca(H2PO4)2·H2O et de sa reaction avec CaSO4 par ATD-ATG couplees

The dehydration of Ca(H₂PO₄)₂·H₂O was examined with simultaneous DTA and TG. This dehydration permitted clearly the apparation of the following phases: Ca(H₂PO₄)₂·0.5H₂O, Ca(H₂PO₄)₂, Ca₃(HP₂O₇)₂, Ca₂HP₃O₁₀ et Ca(PO₃)₂. The reaction of Ca(H₂PO₄)₂·H₂O and CaSO₄ was also examined with the same technics. It was found that the decomposition of CaSO₄ takes place for relatively low temperature (between 600°C and 800°C).     

Highly Efficient Synthesis of Substituted Benzenes in the Presence of B(HSO4)3 as a New and Reusable Catalyst Under Solvent-Free Conditions

A highly efficient and simple procedure for the synthesis of substituted benzenes is described. A broad range of ketones (alkyl–aryl ketones and cyclic ketones) were condensed via a cyclotrimerization reaction in the presence of catalytic amounts of boron sulfonic acid [B(HSO₄)₃], a new, highly efficient, and reusable catalyst, under solvent-free conditions. All reactions completed in short times without formation of any by-products. The catalyst was recovered and reused successfully for 15 cycles of the reaction.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

A simple conversion of azlactones into indenones via H3PW12O40/Al2O3 catalyzed intramolecular Friedel-Crafts reaction

A rapid and simple procedure for the synthesis of the indenone derivatives, N-(1-oxo-1H-inden-2-yl)benzamides, via intramolecular Friedel-Crafts (IFC) reaction of (Z)-4-arylidene-2-phenyl-5(4)-oxazolones (azlactones) catalyzed by H₃PW₁₂O₄₀ supported on neutral alumina under microwave irradiation has been developed. The reaction is straightforward and allows easy isolation of the product. The catalyst could be re-used up to four times after simple filtration.     

Synthesis and characterization of a new cyclic phosph(V)azane ligand [(C6H5N)P(O)H]2 and its zinc(II) complex

The new cyclic phosph(V)azane ligand [(C₆H₅N)P(O)H]₂ (2) is obtained from the reaction between PCl₃ and PhNH₂ in toluene followed by controlled hydrolysis of the product in an H₂O–CHCl₃ solution. Compound 2 is the first example of P(V) dimer [(µ-NC₆H₅)P(H)=O]₂, a P₂N₂ ring with two P(O)H moieties. The reaction of 2 with ZnCl₂ in a molar ratio of 1?:?1 in tetrahydrofuran yields the cyclophosph(V)azane complex Cl₂Zn[(C₆H₅N)P(O)H]₂ (3) in which Zn–O bonds form directly between a cyclic phosph(V)azane ligand and Zn(II). The products have been characterized by infrared, multinuclear (¹H, ³¹P, ¹³C) NMR, mass spectrometry, and elemental analysis.     

Synthesis and properties of MoO3/ZrO2 solid acid catalysts for the preparation of polydimethylsiloxane (PDMS) via octamethylcyclotetrasiloxane (D4) ring-opening

A series of MoO₃/ZrO₂ catalysts were prepared by impregnation method, and characterized by X-ray diffraction (XRD), specific surface area (BET) and temperature-programmed desorption of NH₃ (NH₃-TPD). The polydimethylsiloxane (PDMS) was prepared by ring-opening polymerization from D₄ and MM with MoO₃/ZrO₂ catalysts. The effects of MoO₃/ZrO₂ catalysts preparation conditions on PDMS molecular weight and reaction conversion rate were discussed. Moreover, the effects of reaction conditions on the ring-opening polymerization were also studied. During the preparation of PDMS, the molecular weight of the product can be controlled by adjusting the mass ratio of D₄:MM. The MoO₃/ZrO₂ catalyst was compared with other catalysts during the ring-opening process, and the repeated times of MoO₃/ZrO₂ catalysts were also studied. The results showed that MoO₃/ZrO₂ catalyst had more excellent catalytic performance, for ring-opening process, and when the repeated times was more than 5, the catalytic activity decreased significantly. In addition, the kinetics of D₄ ring-opening polymerization with the MoO₃/ZrO₂ catalyst was investigated.