Synthesis of pyrazolopyridines catalyzed by nano-CdZr4(PO4)6 as a reusable catalyst

Research on Chemical Intermediates - A simple and efficient method for the preparation of pyrazolopyridines by a multicomponent reaction of ethyl acetoacetate, an aldehyde, hydrazine and ammonium...     

Cesium Salt of Tungstosilicic Acid Fabricated by Nano-Casting Strategy: An Efficient Catalyst for the Three-Component Hosomi–Sakurai Reaction

Abstract

We have used SBA-15 silicas as hard templates for the nano-fabrication of Cs_1.8H_2.2SiW₁₂O₄₀ (CsHSiW) salt nanocrystal. The elimination by HF (or NaOH 90 °C) in the silica matrix from the composites occurred by a two-step reaction deposition of CsHSiW salt nanocrystal. The nano-casted CsHPW materials were characterized by several techniques: chemical analysis (atomic absorption, neutron activation analysis, and inductively coupled plasma) and spectroscopic methods (FT-IR spectrum, X-ray diffraction, transmission electron microscopy, and energy dispersive x-ray analysis measurement). In addition to the complete characterization of CsHSiW nanocrystal samples, their catalytic performances are shown for the three-component Hosomi–Sakurai reaction. The reaction proceeds efficiently under ambient conditions with good to excellent yields.

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.     

Stochastic non-convex envelopment of data: Applying isotonic regression to frontier estimation

Isotonic nonparametric least squares (INLS) is a regression method for estimating a monotonic function by fitting a step function to data. In the literature of frontier estimation, the free disposal hull (FDH) method is similarly based on the minimal assumption of monotonicity. In this paper, we link these two separately developed nonparametric methods by showing that FDH is a sign-constrained variant of INLS. We also discuss the connections to related methods such as data envelopment analysis (DEA) and convex nonparametric least squares (CNLS). Further, we examine alternative ways of applying isotonic regression to frontier estimation, analogous to corrected and modified ordinary least squares (COLS/MOLS) methods known in the parametric stream of frontier literature. We find that INLS is a useful extension to the toolbox of frontier estimation both in the deterministic and stochastic settings. In the absence of noise, the corrected INLS (CINLS) has a higher discriminating power than FDH. In the case of noisy data, we propose to apply the method of non-convex stochastic envelopment of data (non-convex StoNED), which disentangles inefficiency from noise based on the skewness of the INLS residuals. The proposed methods are illustrated by means of simulated examples.     

Co(III) complexes of Me-salpn and Me-salbn and the ring size effect on the coordination modes and electrochemical properties: The crystal structures of trans-[Co(Me-salpn)(py)2]PF6 and cis-α-[Co(Me-salbn)(4-Mepy)2]BPh4 · 4-Mepy

The synthesis and characterization of a series of cobalt(III) complexes of the general type [Co(N₂O₂)(L₂)]⁺ are described. The N₂O₂ Schiff base ligands used are Me-salpn (H₂Me-salpn = N,N′-bis(methylsalicylidene)-1,3-propylenediamine) (1–3) and Me-salbn (H₂Me-salbn = N,N′-bis(methylsalicylidene)-1,4-butylenediamine) (4–5). The two ancillary ligands L include: pyridine (py) 1, 3-metheylpyridine (3-Mepy) 2, 1-methylimidazole (1-MeIm) 3, 4-methylpyridine (4-Mepy) 4 and pyridine (py) 5. These complexes have been characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structures of trans-[Co^III(Me-salpn)(py)₂]PF₆, 1, and cis-α-[Co^III(Me-salbn)(4-Mepy)₂]BPh₄ · 4-Mepy, 4, have been determined by X-ray diffraction. Examination of the solution and crystalline structures revealed that the outer coordination sphere of the complexes exerts a noticeable influence on the inner coordination sphere of the Co(III) ion. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial (R-py)–cobalt bonds. It has also been observed that the Co(III) state is stabilized with increasing the flexibility of the ligand environment.     

Screening of several biological activities induced by different sesquiterpene lactones isolated from Centaurea behen L. and Rhaponticum repens (L.) Hidalgo

This study aims to evaluate the in vitro cytotoxic, in vitro and in ovo anti-angiogenic effects and antimicrobial activity of sesquiterpene lactones (SLs) from two plants Centaurea behen and Rhaponticum repens (L.). Five SLs, including cynaropicrin (1), 4β,15-dehydro-3-dehydrosolstitialin A (2), aguerin B (3), janerin (4), cebellin E (5), and a flavone hispidulin (6) were isolated from C. behen (compounds 1–3) and R. repens (compounds 4–6). Cynaropicrin (1) and aguerin B (3) were characterised by strong cytotoxic activities against A2780 cells with IC₅₀ values of 1.15 and 1.62 μg mL^?1, respectively, comparable to that of doxorubicin (IC₅₀ = 1.17 μg mL^?1). The anti-angiogenic study showed the remarkable inhibitory effect of cynaropicrin (1) and aguerin B (3) on the proliferation and migration of HUVECs. In addition, cynaropycrin and aguerin B exhibited significant angio-inhibitory effects in CAM assay. These findings may be useful for the development of novel chemotherapeutic agents for the treatment of cancer.     

The Influence of Solvent on the Structural Properties of trans-(NHC)PtI2Py Complex: A Platinum-Based Anticancer Drug

Russian Journal of Physical Chemistry A - Quantum chemical calculations using MPW1PW91 method were applied to analyze the solvent effect on the structural, spectral, and thermochemical parameters...     

Synthesis of novel symmetrical bis‐schiff bases of 5,5′‐methylenebis(2‐aminothiazole)

Novel symmetrical bis‐Schiff bases have been prepared cleanly and efficiently in the presence of formic acid catalyst in methanol from the reaction of symmetrical primary bis‐amine of 5,5′‐methylenebis(2‐aminothiazole) ( 1 ) and a series of aromatic aldehyde derivatives under mild conditions. The advantages of this reaction are simplicity of the reaction procedure, simple work‐up and pure products with high yields. The structures of all the new synthesized symmetrical bis‐Schiff bases were confirmed by elemental analyses, IR, ¹H‐NMR, ¹³C‐NMR and mass spectra.     

Nickel(II) Complexes with a Hydroxyl Pendant‐Armed Macrocyclic Ligand: Synthesis,Characterization, and Crystal Structures

The reactions of different nickel(II) salts with a mixed‐donor macrocyclic ligand L (6,7,8,9,10,11,18,19‐octahydro‐5H, 17H‐dibenzo[f,o][1,5,9,13] dioxadiazacyclohexadecin‐18‐ol), potentially pentadentate N₂O₃ donor sets containing one pendant alcohol function have been investigated. The physical properties and the chemical structures of 1:1 (metal:ligand) NiLX₂ (X = Cl^?, Br^?, NO₃^?, ClO₄^?) complexes have been characterized by using IR, UV‐Vis spectroscopy and conductance measurements. The X‐ray determination have been employed to probe the nature of the respective complexes in solid state. The nickel atom in [NiL(NO₃)]NO₃·0.5H₂O complex is six‐coordinate with a distorted octahedral coordination in which the all N₂O₃ donor atoms are coordinated to the nickel atom. The coordination sphere is completed by a nitrate anion. In contrast to the above nickel complex, in [NiLCl₂] complex the pendant hydroxyl arm of macrocycle remains uncoordinated and ligand acts as tetradentate N₂O₂ donor atoms. The coordination sphere is completed by two chloride anions and the nickel atom is six‐coordinate with a distorted octahedral coordination.