Green synthesis and characterization of novel 1,2,4,5-tetrasubstituted imidazole derivatives with eco-friendly red brick clay as efficacious catalyst

Use of cheaper and recyclable materials contributes positively to economic growth with environmental sustainability. We report the prospect of utilizing red brick clay as catalyst, which exhibited excellent activity in rapid one-pot four-component condensation of 1,2,4,5-tetrasubstituted imidazoles with high conversion and yields (91–96%) in aqueous medium at 60 °C in short reaction times (25–40 min). The red brick clay material was fully characterized by XRD, FT-IR, SEM, TEM, EDX and BET analyses. Red brick clay consisted of oxides of Si (20.38%), Fe (19.55%), Al (14.30%) and minor amounts of Ca (3.60%) and Mg (1.68%). The slate-like-shaped structure morphology and flaky appearance of inexpensive solid clay material proved competent material for the synthesis of 15 novel 1,2,4,5-tetrasubstituted imidazole derivatives. In addition, the advantages of the eco-friendly method are non-toxicity and re-usability of the catalyst. Reaction offers 78% atom economy and 84% carbon capture.

     

Rearrangements in Scholl Reaction

Rearrangements in Scholl reaction are mostly serendipitous. The design of molecular precursors is what seems to guide the course of rearrangement. This review consolidates different classes of precursors used in Scholl reaction and their accompanying rearrangements that include aryl migration, migration followed by cyclization and skeletal rearrangements involving ring expansion, ring contraction and both, under the reaction conditions. The attempt in collating heretofore-reported examples in this review is to guide designing appropriate precursors to predictably achieve complex molecular structures or nanographenes or defect-nanographenes via rearrangement.     

Facile one-pot green synthesis of 2-amino-4H-benzo[g]chromenes in aqueous ethanol under ultrasound irradiation

Abstract

We report an efficient green one-pot approach for the synthesis of eighteen novel dihydro-4H-benzo[g]chromene derivatives under ultrasound irradiation conditions. The three-component condensation reaction proceeded through Knoevenagel-Michael reaction of chosen active methylene compounds and 2-hydroxynaphthalene-1,4-dione with different substituted aldehydes in the presence of ammonium acetate in water and ethanol mixture at room temperature, which furnished high yields of products (91–98%) in a rapid reaction time of 5–15?min. This procedure offers 95% of the atom economy and 100% of carbon efficiency together with other eco-friendly benefits.     

A facile and straightforward synthesis of 1,2,3-thiadiazoles from α-enolicdithioesters via nitrosation/reduction/diazotization/cyclization cascade in one-pot

An operationally simple, economical, and straightforward synthesis of diverse 4,5-disubstituted 1,2,3-thiadiazoles from α-enolicdithioesters has been achieved via nitrosation/reduction/diazotization/cyclization sequence in one-pot through the formation of cascade 1–2 (N–S) and 3–4 (C–N) bonds. Importantly, this is the first straightforward entry to highly functionalized 1,2,3-thiadiazoles from dithioesters.     

Microwave assisted one-pot synthesis of linear and angular furo chromanone scaffolds and their in vitro antimicrobial activity

Russian Journal of General Chemistry - A new series of linear and angular alkyl substituted furochromanone derivatives have been synthesized in one pot microwave irradiation assisted process from...     

Progressive addition of GO to TiO2 nanowires for remarkable changes in photochemical hydrogen production

Addition of 2D GO to the TiO₂ nanowires brings about progressive changes in the optical properties and photochemical hydrogen production. The composition with progressive addition of GO played a dramatic role in making the material blue shift. The blue shift may happen due to transition from O²⁻ anti-bonding orbital to the Ti⁴⁺ lowest empty orbital and also the process of band shifting towards lower wavelength is attributed to quantum confinement effect which occurs due to the transformation of bulk titanate to nanostructure titanate. In this article, we present the results of TiO₂ nanowires and its rGO composites. TiO₂ with 30 mg rGO nanocomposite exhibits good UV-light induced hydrogen production unlike bare TiO₂. Current studies explain how rGO addition can be employed for better hydrogen production.

     

Composite heat transfer in a variable porosity medium bounded by an infinite flat plate

Heat transfer by simultaneous radiation and convection in a variable porosity medium bounded by an infinite flat plate is determined by solving momentum and energy equations. The problem is investigated for two different cases, viz., presence of porous medium and absence of porous medium. In the presence of porous medium both variable and constant porosity situations are studied. Similarity solutions are obtained for an isothermal and impermeable wall. The Kozeny-Blake expression connecting porosity and permeability is incorporated in the analysis for unified treatment. A parameter survey is made to study the effect of optical thickness, porous parameter, albedo scattering and ratio of conduction to radiation using Runge-Kutta-Gill method. The heating and cooling cases are considered for variable porosity situation. The results show that both convective and radiative components decrease with increase in porous parameter, and the inhomogeneity of the medium enhances heat transfer rate. The increase in optical thickness leads to decrease in both convective and radiative fluxes. For a particular value of wall emissivity ( _w =0.5932116) the radiative flux is reduced to zero.

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Kombinierter Wärmeübergang in einem durch eine unendlich ausgedehnte ebene Platte begrenzten Medium variabler Porosität

Zusammenfassung Der Wärmeübergang bei gleichzeitigem Einfluß von Strahlung und Konvektion in einem Medium variabler Porosität, das durch eine unendlich ausgedehnte ebene Platte begrenzt ist, wird durch Lösung der Impuls- und Energiegleichung bestimmt (den Sonderfall, daß nur Fluid, aber kein poröses Medium vorliegt, eingeschlossen). Im allgemeinen Fall — mit porösem Medium — wird sowohl variable, wie auch konstante Porosität unterstellt. Für die isotherme und stoffundurchlässige Wand existieren Ähnlichkeitslösungen. Um eine einheitliche mathematische Behandlung zu ermöglichen, wird die (Porosität und Permeabilität verknüpfende) Beziehung nach Kozeny-Blake eingeführt. Eine Parameterstudie, durchgeführt unter Verwendung der Runge-Kutta-Gill-Methode, zeigt den Einfluß der optischen Dicke, des Porositätsparameters, der Albedo-Streuung und des Verhältnises von Leitung zu Strahlung. Die Fälle Heizung und Kühlung wurden bei variabler Porosität untersucht. Aus den Ergebnissen geht hervor, daß die Konvektions- und Strahlungsanteile mit zunehmenden Porositätsparameter abnehmen und daß der Wärmeübergang durch Inhomogenität des Mediums verbessert wird. Zunehmende optische Dicke verusacht eine Abnahme sowohl des Konvektions- wie des Strahlungsflusses. Beim Wert _w =0.5932116 des Wandemissionsverhältnisses fällt der Strahlungsfluß auf Null ab.

     

Composite heat transfer in case of steady laminar flow of a gray fluid with large optical density past a horizontal plate embedded in a saturated porous medium

The present paper discusses the problem of composite heat transfer and viscous friction of a moving gray medium with large optical density. Expressions for temperature and velocity distributions and the ratio of the radiative component to convective component of heat flux are obtained. It is observed that for a given value ofB the ratio of radiative heat flux to convective heat flux is maximum at the edge of the boundary layer and tends to an asymptotic value as the boundary is reached. However, for a given value ofK δ, the ratio of heat fluxes increases with increase inB (the porous parameter). The results also show that as the wall temperature approaches the value of free stream temperature, the ratio of heat fluxes decreases.     

Comparison and correlation of in vitro, in vivo and in silico evaluations of alpha, beta and gamma cyclodextrin complexes of curcumin

In the present study investigated the effect of curcumin (CUR) alpha (α), beta (β) and gamma (γ) cyclodextrin (CD) complexes on its solubility and bioavailability. CUR the active principle of turmeric is a natural antioxidant agent with potent anti-inflammatory activity along with chemotherapeutic and chemopreventive properties. Poor solubility and poor oral bioavailability are the main reasons which preclude CUR use in therapy. Extent of complexation was β-CD complex (82 %) > γ-CD (71 %) > α-CD (65 %). Pulverization method resulted in significant enhancement of CUR (0.002 mg/ml) solubility with CUR α-CD complex (0.364 mg/ml) > CUR β-CD complex (0.186 mg/ml) > CUR γ-CD complex (0.068 mg/ml). Gibbs-free energy and in silico molecular docking studies favour formation of α-CD complex > β-CD complex > γ-CD complex. With reference to CUR, relative bioavailability of CUR α-CD, CUR β-CD and CUR γ-CD complexes were 460, 365 and 99 % respectively. CUR–CD complexes exhibited increased bioavailability with an increase in t_½, tmax, Cmax, AUC, Ka, and MRT; and a decrease in Ke, clearance and Vd values. AUC increase was CUR α-CD complex > CUR β-CD complex > CUR γ-CD complex. Significant difference (p < 0.05) was observed between CUR α-CD complex and CUR γ-CD complex by one-way ANOVA and Dunnett’s post hoc test for multiple comparison analysis. Correlation observed between in vitro, in vivo and in silico methods indicates potential of in silico and in vitro methods in CD selection.