γ‐PCC and γ‐PCC‐SiO2 as Efficient Reagents for Oxidation of Thiols to Disulfides

Abstract

Oxidative coupling of thiols to the corresponding symmetrical disulfides was performed in the presence of γ‐picolinium chlorochromate and its silica gel supported. The reactivity of silica gel supported γ‐picolinium chlorochromate for thiophenol derivatives is more than the reactivity of pyridinium and γ‐picolinium chlorochromates.     

(NH4)3PW12O40 as an Efficient and Reusable Catalyst for the Synthesis and Deprotection of 1,1‐Diacetates

An efficient method for the synthesis of 1,1‐diacetates (acylals) from different aldehydes in the presence of (NH₄)₃PW₁₂O₄₀ and acetic anhydride under solvent‐free conditions at ambient temperature is achieved. Selective conversion of aldehydes was observed in the presence of ketones. The deprotection of acylals has also been achieved using (NH₄)₃PW₁₂O₄₀ in methanol. The catalyst was found to possess good activity and considerable level of reusability.     

A New Application of N,N ′-dibromo-N,N ′–1,2-ethanediylbis(p-toluenesulfonamide) as Selective and Efficient Reagent for the Oxidation of Various Thiols to Disulfides

ABSTRACT

An efficient method for oxidation of thiol to their corresponding disulfides in high yields with N, N^′-Dibromo-N,N^′–1,2-ethanediyl bis (p-toluensulphonamide) in dichloromethane at room temperature is described.     

Analysis of (NH4)6Mo7O24·4H2O thermal decomposition in argon

Nanometric carbides of transition metals and silicon are obtained by using precursors. Control of the course of these processes require data concerning transformations of single precursor, transformations of precursor in the presence of reducing agent and synthesis of the carbide. In this work, the way of investigating such processes is described on the example of thermal decomposition of (NH₄)₆Mo₇O₂₄·4H₂O (precursor) in argon. The measurements were carried out by TG–DSC method. The solid products were identified by XRD method, and the gaseous products were determined by mass spectrometry method. There was demonstrated that the investigated process proceeded in five stages. Kinetic models (forms of f(α) and g(α) function) most consistent with experimental data and coefficients of Arrhenius equation A and E were determined for the stages. The Kissinger method and the Coats–Redfern equation were applied. In case of the Coats–Redfern equation, the calculations were performed by analogue method. In this way good consistency between the calculated and determined conversion degrees α(T) at practically constant values of A and E were obtained for distinguished stages and different sample heating rates.     

Wet Carbon‐Based Solid Acid/Potassium Bromate as an Efficient Heterogeneous Reagent for Oxidation of Alcohols under Mild Conditions

Wet carbon‐based solid acid and potassium bromate were used as new reagent for oxidation of alcohols to their corresponding aldehyde or ketone derivatives in dichloromethane with good yields.     

Potassium Dodecatungstocobaltate Trihydrate (K5CoW12O40 · 3H2O) as an Efficient Catalyst for Aminolysis of Epoxides

Abstract

Aminolysis of epoxides using various amines was catalyzed with potassium dodecatungstocobaltate trihydrate in a convenient and efficient method with good selectivities.     

Perchloric Acid–Doped Polyaniline as an Efficient and Reusable Catalyst for the Synthesis of 2-Substituted Benzothiazoles

2-Substituted benzothiazoles have been efficiently synthesized in good yields by the condensation reaction of o-aminothiophenol with aldehydes in the presence of a catalytic amount of perchloric acid–doped polyaniline (HClO₄/PANI). The low cost, simple recovery, and efficient reusability are remarkable characteristics of this catalyst.     

Diels-Alder Reactions of N-Functionalized Acryloyl α-Pyrrolidone Derivatives Using FeCl3·6H2O as an Efficient Catalyst under Solvent-free Conditions

Diels-Alder reactions of N-functionalized acryloyl α-pyrrolidone derivatives were investigated, which were catalyzed by FeCl3·6H2O as an efficient catalyst under solvent-free conditions at room temperature. The corresponding cycloadducts with functionalized-pyrrolidone were prepared in high yield with high stereoselectivity by a green chemistry procedure. N-Functionalized acryloyl pyrrolidone derivatives, a kind of pyrrolidone-functionalized chelating α,β-unsaturated ketone usable as a dienophile in Diels-Alder reaction, were synthesized by N-acylation procedure in ionic liquid as a novel synthetic method.     

VCl3‐Catalyzed Selective Oxidation of Sulfides to Sulfoxides Using H2O2 as Oxidant

VCl₃ is an effective catalyst for the catalytic oxidation of sulfides to afford sulfoxides in good yields using hydrogen peroxide as an oxidant.     

Novel Method for Preparing NH4NiPO4·6H2O: Hydrogen Bonding Coacervate Selective Self-assembly

The single phase NH₄NiPO₄·6H₂O was synthesized by solid‐state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. The NH₄NiPO₄·6H₂O and its calcined products were characterized using X‐ray powder diffraction (XRD), thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform IR (FT‐IR), ultraviolet‐visible (UV‐vis) absorption spectroscopy, and scanning electron microscopy (SEM). The results showed that the product dried at 80°C for 3 h was orthorhombic NH₄NiPO₄·6H₂O [space group Pmm2(25)], and surfactant polyethylene glycol (PEG)‐400 can direct growth of crystal NH₄NiPO₄·6H₂O. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involve the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. The product of thermal decomposition at 150°C for 2 h, orthorhombic NH₄NiPO₄·H₂O, is layered compound with an interlayer distance of 0.8370 nm.     

Cu(ClO4)2 · 6H2O as an Efficient Catalyst for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Under Solvent-Free Conditions

Cu(ClO₄) · 6H₂O efficiently catalyzes the three-component Biginelli reaction of aldehyde, β-dicarbonyl compounds, and urea or thiourea under solvent-free conditions to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones in excellent yields.      

Ce(SO4)2·4H2O as a Recyclable Catalyst for an Efficient,Simple, and Clean Synthesis of 4H-Benzo[b]pyrans

An efficient method for the synthesis of 4H-benzo[b]pyrans has been developed by the use of Ce(SO₄)₂·4H₂O (2.5 mol%) as a catalyst. Heating the mixture of an appropriate aldehyde, malononitrile, and dimedone in the presence of the catalyst at 45°C in a mixture of water:ethanol (1:1) as solvent for about 9–55 min resulted excellent yields of the corresponding products. Short experimental time of the reaction, excellent yields, simple workup, not using cumbersome apparatus for purification of the products, and inexpensiveness and commercially availability of the catalyst are the advantages of this method.     

P2O5/SiO2 as a New,Efficient, and Reusable Catalyst for Preparation of β-Enaminones Under Solvent-Free Conditions

P₂O₅/SiO₂ (30% w/w) was applied as an efficient, heterogeneous, and reusable catalyst for the synthesis of β-enaminones. The reactions were rapidly completed at 80 °C under solvent-free conditions and products were obtained in good to excellent yields.     

Mild and Efficient Procedure for Michael Addition of N-Heterocycles to α,β-Unsaturated Compounds Using Anhydrous K3PO4 as Catalyst

Imidazole, 1,2,4-triazole, indole, and benzotriazole undergo conjugate additions with α, β-unsaturated carbonyl compounds in the presence of anhydrous potassium phosphate at ambient temperature to afford the corresponding Michael adducts in excellent yields.     

Scandium(III) Triflate as an Efficient and Reusable Catalyst for Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones

Sc(III) triflate efficiently catalyzes the three‐component condensation reaction of an aldehyde, a β‐ketoester, and urea in refluxing acetonitrile to afford the corresponding 3,4‐dihydropyrimidin‐2(1H)‐ones in excellent yields. The catalyst can be recovered and reused, making this method friendly and environmentally acceptable.     

Cu(NO3)2 · 3 H2O as an Efficient Reagent for the Chemoselective Trimethylsilylation of Primary Alcohols and Oxidation of Trimethylsilyl Ethers

Abstract

Cu(NO₃)₂ · 3 H₂O can be used as an efficient reagent for the chemoselective trimethylsilylation of primary benzylic and aliphatic alcohols with hexamethyldisilazane (HMDS). This reagent is also able to oxidize the obtained trimethylsilyl ethers to the corresponding carbonyl compounds in the presence of wet SiO₂ and KBr. In this study, all reactions are performed in the absence of a solvent and good-to-high yields are obtained.     

Efficient Transition‐Metal‐Free Oxidation of Benzylic and Secondary Alcohols to the Carbonyl Compounds Using an N‐Bromosuccinimide/NH4Cl System

The oxidation of a variety of benzylic and secondary alcohols was achieved in excellent yields using an NBS/NH₄Cl system in aqueous acetonitrile (CH₃CN‐H₂O; 7/3 v/v) at 80°C under very mild conditions.     

Facile Synthesis of Bis(indolyl)methanes Using LaCl3 · 7H2O as a Mild and Efficient Catalyst in Molten Salt Media

Efficient electrophilic substitution reaction of indole with various carbonyl compounds were carried out using a catalytic amount of LaCl₃ · 7H₂O in molten tetraethylammonium chloride as an ionic liquid to afford the corresponding bis(indolyl)methanes in excellent yields.     

γ-Al2O3-Supported 12-Tungstosilicic Acid as an Efficient Heterogeneous Catalyst for the Synthesis of α-Aminonitrile

The multicomponent Strecker reaction using trimethylsilyle cyanide was performed in very short reaction times, and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of alumina-supported tungstosilicic acid.