Polyethylene Glycol as Support and Phase Transfer Catalyst in Aqueous Palladium-catalyzed Liquid-phase Synthesis

Recently, the liquid-phase synthesis of small organic compounds has been a preferable strategy due to its combination with the advantage of solution-phase and solid-phase methods1. Among the various soluble polymers, polyethylene glycol (PEG) is the most useful as support. It has been reported that PEG bound substrates could also play the role of phase-transfer catalyst (PTC) in some reactions2. Herein we reported that palladium-catalyzed coupling reactions could be taken place smoothly…     

Asymmetric Synthesis of Densely Functionalized Medium‐Ring Carbocycles and Lactones through Modular Assembly and Ring‐Closing Metathesis of Sulfoximine‐Substituted Trienes and Dienynes

An asymmetric synthesis of densely functionalized 7–11‐membered carbocycles and 9–11‐membered lactones has been developed. Its key steps are a modular assembly of sulfoximine‐substituted C‐ and O‐tethered trienes and C‐tethered dienynes and their Ru‐catalyzed ring‐closing diene and enyne metathesis (RCDEM and RCEYM). The synthesis of the C‐tethered trienes and dienynes includes the following steps: 1) hydroxyalkylation of enantiomerically pure titanated allylic sulfoximines with unsaturated aldehydes, 2) α‐lithiation of alkenylsulfoximines, 3) alkylation, hydroxy‐alkylation, formylation, and acylation of α‐lithioalkenylsulfoximines, and 4) addition of Grignard reagents to α‐formyl(acyl)alkenylsulfoximines. The sulfoximine group provided for high asymmetric induction in steps 1) and 4). RCDEM of the sulfoximine‐substituted trienes with the second‐generation Ru catalyst stereoselectively afforded the corresponding functionalized 7–11‐membered carbocyles. RCDEM of diastereomeric silyloxy‐substituted 1,6,12‐trienes revealed an interesting difference in reactivity. While the (R)‐diastereomer gave the 11‐membered carbocyle, the (S)‐diastereomer delivered in a cascade of cross metathesis and RCDEM 22‐membered macrocycles. RCDEM of cyclic trienes furnished bicyclic carbocycles with a bicyclo[7.4.0]tridecane and bicyclo[9.4.0]pentadecane skeleton. Selective transformations of the sulfoximine‐ and bissilyloxy‐substituted carbocycles were performed including deprotection, cross‐coupling reaction and reduction of the sulfoximine moiety. Esterification of a sulfoximine‐substituted homoallylic alcohol with unsaturated carboxylic acids gave the O‐tethered trienes, RCDEM of which yielded the sulfoximine‐substituted 9–11‐membered lactones. RCEYM of a sulfoximine‐substituted 1,7‐dien‐10‐yne showed an unprecedented dichotomy in ring formation depending on the Ru catalyst. While the second‐generation Ru catalyst gave the 9‐membered exo 1,3‐dienyl carbocycle, the first‐generation Ru catalyst furnished a truncated 9‐membered 1,3‐dieny carbocycle having one CH₂ unit less than the dienyne.     

Electrostatic contribution to the ion solvation energy: cavity effects

Ion solvation process has been analysed for the spherically symmetrical system where an ion is located inside a cavity surrounded by an isotropic nonlocal dielectric medium. It has been proven that for any dielectric properties of the medium, the electric field outside the cavity as well as the ion solvation energy depend only on the total ion charge but not of the particular distribution of the ion charge density inside the cavity. These characteristics remain unchanged if the charge is displaced from the external boundary of the cavity into it. Analytical formulas for them have been derived for a particular model of the nonlocal dielectric function. Comparison of results for the solvation energy on the basis of this new theory and of the conventional approach (disregarding the existence of the cavity) shows a significant difference between their predictions if the ion charge is displaced inside the ion cavity.     

A hybrid nanofluid analysis near a parabolic stretched surface

Two dimensional incompressible steady viscous nano-fluid flow with the impacts of heat generation and porous medium is examined numerically. For this objective Ti₆Al₄v are taken as nano-particles dispersed in different base fluids such as methanol, engine oil and water. Basically in this study we will compare three different nano-fluids to assess their flow behaviour and thermal performance. The flow model is developed under certain assumptions. The two dimensional non-linear PDEs are converted into non-linear ODEs with suitable transformation. The numerical procedure is adopted to find the results by using Bvp4c technique in MATLAB. Moreover, graphs are generated for various parameters against the temperature and velocity profiles. The fluid behaviour for different parameter is examined on velocity and temperature profile. It is depicted that for high values of volume fraction and curvature parameter nano-particles leads to high velocity and temperature profile. Moreover, velocity profile decreases for permeability parameter, while temperature profile enhances for heat generation parameter. The influence of Nusselt number and skin friction also assessed. The model of entropy generation is also presented.     

γ-Valerolactone (GVL) as a green and efficient dipolar aprotic reaction medium

The great challenge for modern research is to define the most efficient tools to make more sustainable the industrial production and manufacturing. Among the different aspects that require attention the replacement of toxic and/or non-renewable solvents it is certainly playing a crucial role. Dealing with widely used dipolar aprotic solvents, among the different alternatives proposed in the literature γ-valerolactone (GVL) plays a pivotal role covering different application area. In this contribution, the benefits derived from the use of GVL as a circular, safe, biomass-derived reaction medium are highlighted covering most recent publications (2021). The presentation has been divided into three major sections: (i) biomass valorization, (ii) materials synthesis, manufacturing and recycle and (iii) new synthetic methodologies.     

The extraction,antioxidant and against β-amyloid induced toxicity of polyphenols from Alsophila spinulosa leaves

Alsophila spinulosa is a tree-like fern, and many evidences suggested that plant polyphenols had the potential therapeutic for Alzheimer s disease (AD). Herein, polyphenols (ASP) was isolated from A. spinulosa leaves and its major constituent were isoorientin and vitexin. ASP displayed excellent antioxidant activity and obvious anti-lipid peroxidation capacity in vitro. ASP improved the survival rate of C. elegans under high temperature by enhancing the antioxidant enzymes activities and decreasing the lipid peroxidation level. Moreover, ASP alleviated β-amyloid (Aβ) induced paralysis and reduced Aβ deposition, decreased reactive oxygen species (ROS) accumulation and improved the level of skn-1 mRNA. In addition, ASP decreased the levels of pdk-1 and akt-1 mRNA in P13K/AKT signaling pathway. In conclusion, ASP may be a potential ingredient for the alleviation of AD.     

Optimized POCl3-assisted synthesis of 2-amino-1,3,4-thiadiazole/1,3,4-oxadiazole derivatives as anti-influenza agents

Although recent decades have witnessed the synthesis of 1,3,4-thiadiazoles via phosphorus POCl₃-promoted cyclization reaction, simultaneous access to 2-amino-1,3,4-thiadiazole and 2-amino-1,3,4-oxadiazole analogs remains unexpected and elusive. Herein, a detailed regiocontrolled synthesis of 2-amino-1,3,4-thiadiazoles in good to high yields with good regioselectivities from readily available thiosemicarbazides using POCl₃ was disclosed. Meantime, to establish a comprehensive structure–activity relationship, 2-amino-1,3,4-oxadiazole derivatives as single regioisomers were prepared via EDCI·HCl-triggered cyclization of the thiosemicarbazide intermediates. The in vitro anti-influenza assays proved that the selected compounds with the pyrazine/pyridine ring exhibited certain inhibitory activities against influenza A virus strains A/HK/68 (H3N2) and A/PR/8/34 (H1N1) in MDCK cells. Among them, N-(adamantan-1-yl)-5-(5-(azepan-1-yl)pyrazin-2-yl)-1,3,4-thiadiazol-2-amine (4j) was the most active compound, and exhibited favorable activity with EC₅₀ values of 3.5 μM and 7.5 μM, respectively. In addition, the molecular docking results explained the reason why compound 4j had dual inhibitory activity and revealed the reasonable binding mode of this compound with the M2-S31N and M2-WT ion channels. This compound had the potential to be further developed as an anti-influenza drug.     

New amides fromSpilanthes oleracea

In addition to the well known affinin [=spilanthol, (2E,6Z,8E)-deca-2,6,8-trienoic acid isobutylamide (1)], the corresponding 2-methyl-butylamide (2), and two new acetylenic alkamides were isolated fromSpilanthes oleracea L. by reversed phase medium pressure chromatography: (Z)-non-2-en-6,8-diynoic acid isobutylamide (3) and (Z)-dec-2-en-6,8-diynoic acid isobutylamide (4). The structures and their stereochemistries were elucidated by¹H-NMR,¹³C-NMR (2 and3), MS, UV, IR, and CD (2). The chemotaxonomic significance of the distribution of alkamides within theCompositae tribeHeliantheae is briefly discussed.

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Neue Amide ausSpilanthes oleracea (Kurze Mitteilung)

Zusammenfassung AusSpilanthes oleracea wurden neben dem seit langem bekannten Affinin [=Spilanthol, (2E,6Z,8E)-Deca-2,6,8-triensäureisobutylamid (1)] durch Umkehrphasen-Mitteldruckchromatographie das entsprechende 2-Methylbutylamid (2) und zwei neue acetylenische Alkamide isoliert: (Z)-Non-2-en-6,8-diinsäure-isobutylamid (3) und (Z)-Dec-2-en-6,8-diinsäure-isobutylamid (4). Die Strukturen und deren Stereochemie wurden mittels¹H-NMR,¹³C-NMR (2 und3), MS, UV, IR und CD (2) aufgeklärt. Die chemotaxonomische Bedeutung der Verbreitung von Alkamiden innerhalb der Compositen-TribusHeliantheae wird kurz diskutiert.

     

Nickel determination in osteoblast-like cell culture medium by adsorptive cathodic stripping voltammetry with a mercury microelectrode

The purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast-like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square-wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10⁻⁴ mol L⁻¹; ammonium chloride buffer: 0.10 mol L⁻¹ (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10⁻⁹ mol L⁻¹ for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays.     

Synthesis of polymers in aqueous solutions: Polyaddition of bis(oxazolines) with dithiol in aqueous solutions

Polyaddition of bis(4-mercaptophenyl) sulfide ( BMPS ) with m-phenylenebis(2-oxazoline) ( MPBO ) proceeded very smoothly in the mixtures of aprotic ploar solvents such as N-methyl-2-pyrrolidone ( NMP ) with water to produce the corresponding poly(amide–sulfide) with high molecular weights at 90°C under nitrogen. The reaction of BMPS with MPBO , p-phenylenebis(2-oxazoline), and 1,4-butylenebis(2-oxazoline) was also examined in water under the same conditions, and it was found that the reaction proceeds successfully to give the corresponding poly(amide–sulfide)s with high molecular weights. These results mean that water along as well as the mixed solvents of aprotic polar solvents such as NMP with water can be uses as suitable reaction media for the polyaddition of bis(oxazolines) with dithiol to synthesize poly(amide—sulfide)s with high molecular weights. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2711–2717, 1997