Sulfonic acid pyridinium chloride-functionalized nanoparticles (MnCoFe2O4@Niacin-SO3H)+Cl− as a novel and reusable catalyst for synthesis of tetrahydrodipyrazolopyridines and pyranopyrazoles

The novel pyridinium chloride-functionalized MnCoFe₂O₄-SO₃H nanoparticles, (MnCoFe₂O₄@Niacin-SO₃H)⁺Cl^?, were synthesized by coating the sulfonic group on the surface of MnCoFe₂O₄@Niacin. The activity of these nanoparticles was studied for the synthesis of tetrahydrodipyrazolopyridines and pyranopyrazole derivatives via the multi-component reactions of ethyl acetate, hydrazine, aldehydes, and ammonium acetate or malononitrile. The use of green solvent, easy separation of the catalyst from the reaction medium, easy deposition, high purity, and openness of products are some advantages of this procedure.

     

Ferric Perchlorate: An Efficient Reagent for Regio- and Stereoselective Alcoholysis and Hydrolysis of Epoxides

Regio- and stereoselective ring opening reaction of epoxides is achieved efficiently by aliphatic alcohols and water in the presence of catalytic amounts of ferric perchlorate.     

Additive-Free Chemoselective Acylation of Amines and Thiols

Summary. Amines with different stereoelectronic nature were efficiently acylated at room temperature using acetic anhydride in the presence of no solvent or additive. Various thiols also react equally well under the same conditions. Chemoselective protection of amines in the presence of thiols, alcohols, and phenols and of thiols in the presence of alcohols, and phenols were achieved using competitive experiments.     

The spectral characterization of graphs of index less than 2 with no path as a component

A graph is said to be determined by the adjacency and Laplacian spectrum (or to be a DS graph, for short) if there is no other non-isomorphic graph with the same adjacency and Laplacian spectrum, respectively. It is known that connected graphs of index less than 2 are determined by their adjacency spectrum. In this paper, we focus on the problem of characterization of DS graphs of index less than 2. First, we give various infinite families of cospectral graphs with respect to the adjacency matrix. Subsequently, the results will be used to characterize all DS graphs (with respect to the adjacency matrix) of index less than 2 with no path as a component. Moreover, we show that most of these graphs are DS with respect to the Laplacian matrix.     

H2SO4/Silicagel: Highly Efficient Catalyst for the Synthesis of α-Aminonitriles Using Trimethysilyl Cyanide

Summary. The multicomponent Strecker reaction using trimethylsilyl cyanide was performed at room temperature and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of H₂SO₄ adsorbed on silica gel.     

Analysis of the vibrational behavior of the composite cylinders reinforced with non-uniform distributed carbon nanotubes using micro-mechanical approach

Nanocomposites are a promising new class of structural materials for the aerospace structural components. This paper presents a detailed theoretical investigation of dynamic characteristics of cylinders made of carbon nanotube-reinforced composites. The cylinders are modeled as a cylindrical shell consisting of an isotropic matrix reinforced with transversely isotropic carbon nanotubes. Two different types of carbon nanotube reinforcements are considered: single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). The effects of carbon nanotube aspect ratio, dispersion, alignment and volume fraction on the elastic modulus are analyzed using the Eshelby–Mori–Tanaka theory. Mass and stiffness matrices are obtained via Ritz method and natural frequencies of the structure are derived through solving the eigenvalue problem. Finally, the effects of the CNT distribution on mode shapes and natural frequencies are discussed.     

On Group Choosability of Total Graphs

In this paper, we study the group and list group colorings of total graphs and present group coloring versions of the total and list total colorings conjectures. We establish the group coloring version of the total coloring conjecture for the following classes of graphs: graphs with small maximum degree, two-degenerate graphs, planner graphs with maximum degree at least 11, planner graphs without certain small cycles, outerplanar graphs and near outerplanar graphs with maximum degree at least 4. In addition, the group version of the list total coloring conjecture is established for forests, outerplanar graphs and graphs with maximum degree at most two.     

A facile, mild and efficient one-pot synthesis of 2-substituted indole derivatives catalyzed by Pd(PPh3)2Cl2

2-Phenylindoles were prepared by heteroannulation of 2-haloaniline derivatives and phenylacetylene under mild conditions in a one-pot reaction catalyzed by Pd(PPh3)2Cl2.     

A Note on Group Choosability of Graphs with Girth at least 4

In this paper we show that the group choice number of a graph without K ₅-minor or K _3,3-minor with girth at least 4 (resp. 6) is at most 4 (resp. 3) and we conclude that these results hold for the group chromatic number, the choice number and the chromatic number.