Synthesis of Dendrimer‐Like Polyindolyl Compounds

Syntheses of polyindolyl compounds from the Friedel–Crafts reaction of indoles and tri‐ or tetra‐aldehydes catalyzed by silica sulfuric acid are described. These dendrimeric supramolecules were effectively prepared at room temperature in quantitative yield. These novel products have potential in the synthesis of dyes and pigments and also in various pharmaceutical applications.     

Nanocrystalline aluminium oxide: a mild and efficient reusable catalyst for the one-pot synthesis of poly-substituted quinolines via Friedlander hetero-annulation

Abstract  

o-Aminoaryl ketones undergo smooth condensation with α-methylene ketones in the presence of nanocrystalline aluminium oxide under mild reaction conditions to afford the corresponding poly-substituted quinolines in excellent yields. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions.     

Nanocomposite of p-type conductive polymer/Cu (II)-based metal-organic frameworks as a novel and hybrid electrode material for highly capacitive pseudocapacitors

In this paper firstly, Cu (II)-based metal-organic framework (MOF; Cu-bipy-BTC, bipy = 2,2′-bipyridine, BTC = 1,3,5-tricarboxylate) was synthesized using chemical approach and then fabricated hybrid poly ortho aminophenol (POAP)/Cu-bipy-BTC films by electropolymerization of POAP in the presence of Cu-bipy-BTC nanoparticles to serve as the active electrode for electrochemical storage device. Surface analysis and electrochemical analysis have been used for characterization of POAP/Cu-bipy-BTC composite film. Different electrochemical methods including galvanostatic charge–discharge experiments, cyclic voltammetry, and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new nanocomposite materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area, and stability in an aqueous electrolyte.     

Recent Strategies in Transition-Metal-Catalyzed Sequential C–H Activation/Annulation for One-Step Construction of Functionalized Indazole Derivatives

Designing new synthetic strategies for indazoles is a prominent topic in contemporary research. The transition-metal-catalyzed C–H activation/annulation sequence has arisen as a favorable tool to construct functionalized indazole derivatives with improved tolerance in medicinal applications, functional flexibility, and structural complexity. In the current review article, we aim to outline and summarize the most common synthetic protocols to use in the synthesis of target indazoles via a transition-metal-catalyzed C–H activation/annulation sequence for the one-step synthesis of functionalized indazole derivatives. We categorized the text according to the metal salts used in the reactions. Some metal salts were used as catalysts, and others may have been used as oxidants and/or for the activation of precatalysts. The roles of some metal salts in the corresponding reaction mechanisms have not been identified. It can be expected that the current synopsis will provide accessible practical guidance to colleagues interested in the subject.     

N2O4/SiO2 system as an efficient reagent for rapid and chemoselective conversion of trimethylsilyl ethers to the parent alcohols under nonaqueous conditions

N₂O₄ was easily impregnated on silica gel to give a stable heterogeneous reagent N₂O₄/SiO₂ (I). Chemoselective deprotection of trimethylsilyl ethers to the corresponding alcohols was achieved in the presence of I in CH₂Cl₂ in excellent yields. The stability, easy preparation and high selectivity of the reagent make this method as a useful procedure for the selective deprotection of TMS ethers at room temperature.     

Silica sulfuric acid as an efficient catalyst for the Friedländer quinoline synthesis from simple ketones and ortho-aminoaryl ketones under microwave irradiation

The synthesis of quinoline derivatives via Friedländer method from ortho-aminoaryl ketones in the presence of a catalytic amount of silica sulfuric acid (SSA) under solvent-free condition and microwave irradiation was described. A good range of simple ketones such as cyclohexanone and deoxybenzoin were used.     

A two-parameter family of an extension of Beatty sequences

Beatty sequences ⌊nα+γ⌋ are nearly linear, also called balanced, namely, the absolute value of the difference D of the number of elements in any two subwords of the same length satisfies D?1. For an extension of Beatty sequences, depending on two parameters s,t∈Z_>0, we prove D?⌊(s-2)/(t-1)⌋+2, and D?2s+1. We show that each value that is assumed, is assumed infinitely often. Under the assumption (s-2)?(t-1)² the first result is optimal, in that the upper bound is attained. This provides information about the gap-structure of (s,t)-sequences, which, for s=1, reduce to Beatty sequences. The (s,t)-sequences were introduced in Fraenkel [Heap games, numeration systems and sequences, Ann. Combin. 2 (1998) 197-210; E. Lodi, L. Pagli, N. Santoro (Eds.), Fun with Algorithms, Proceedings in Informatics, vol. 4, Carleton Scientific, University of Waterloo, Waterloo, Ont., 1999, pp. 99-113], where they were used to give a strategy for a 2-player combinatorial game on two heaps of tokens.     

Oxidation of bisnaphthols to spironaphthalenones,revisited

Bis(2‐hydroxy‐1‐naphthyl)methane derivatives have been efficiently converted to their corresponding spirans through three methods, i.e. oxidation by TCCA under mild reaction conditions, Ph₃Bi catalyzed air oxidation, and by electrochemical reaction. The first two methods are diastereoselective and give either of the two possible diastereomers, while the electrochemical method produces equal amounts of these diastereomers.     

SBA-15/Metformin as a novel sorbent combined with surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) for highly sensitive determination of Pb,Cd and Ni in food and environmental samples

This paper established a new, rapid and sensitive method for the ultra-trace determination of lead, cadmium and nickel in food and environmental samples preconcentrated by dispersive solid-phase extraction (DSPE) combined with surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) prior to graphite furnace atomic absorption spectrometry. SBA-15/Met was synthesized and used as a new efficient sorbent for the extraction of metal ions in DSPE. It was characterized by TEM and TGA techniques. After DSPE step, stripped metal elements were complexed with dithizone, and then, the complexes were extracted into carbon tetrachloride by using SA-DLLME. A conventional nonionic surfactant, triton X-100 was used as a disperser agent. Under the optimized conditions, the limit of quantifications was found to be 2.5 ng L^?1 for Pb²⁺, Cd²⁺ and 5.0 ng L^?1 for Ni²⁺. The limits of detection were 1.5 ng L^?1 for Ni²⁺ and 0.75 ng L^?1 for Pb²⁺ and Cd²⁺, with enrichment factor of 1650. The optimized method exhibited a good precision level with relative standard deviations (RSDs%) values of 4.9, 5.2 and 5.0% for 1 μg L^?1 Pb²⁺, Cd²⁺ and Ni²⁺, respectively (n = 7). Application of the proposed method to the analysis of fish-certified reference material produced results that were in good agreement with the certified values.     

Hydroarylation of cinnamic acid with phenols catalyzed by acidic ionic liquid [H-NMP]HSO<Subscript>4</Subscript>: computational assessment on substituent effect

Hydroarylation of cinnamic acid with different substituted phenols, in the presence of acidic ionic liquid, N-methyl-2-pyrrolidonum hydrosulfate ([H-NMP]HSO₄) gave the corresponding dihydrocoumarins in high yields and excellent selectivity. Among these substituted phenols, while methyl phenol afforded the corresponding dihydrocoumarin, nitrophenol under the same reaction conditions diverted the course of reaction, affording 3-(4-nitrophenyl)-3-phenylpropanoic acids. We investigated this behavior from the energetic and electronic points of view, using quantum chemistry computational methods. In this respect, the electronic energy change values for the conversion reaction of substituted phenyl cinnamate esters to dihydrocoumarin compounds have been obtained via density functional theory calculations. We demonstrated that the conversion reaction in the presence of CH₃ substituent is more favorable energetically than NO₂ substituent. Moreover, we have concentrated on topological analysis of electron density on some key bond and ring critical points and their associated bond paths to assess the conversion of substituted phenyl cinnamate esters to dihydrocoumarins. Our calculated results showed that para-methyl phenyl cinnamate has more of electronic tendency to undergo the intramolecular cyclization step and, consequently, generate the corresponding dihydrocoumarin.