Nucleophilic substitution of α-halo-ketones. XXIII. Acetolysis of 1-chloro-3-phenoxy-1-phenylthio-2-propanones. An intramolecular trans-acetylation involving phenoxide anion as the leaving group

The acetolyses of α-chloro-ketones1a-c,2a-c,9a and11a have been investigated parallely. Several aspects of the mechanisms involved in chlorine normal and cine substitution have been elucidated. Intramolecular trans-acetylation, ultimately leading to fragmentation of acetoxy-ketones3b,4a and4c, have been postulated to account for the formation of thiol ester6, aldehyde5a and ketone5c, respectively.     

Studies of the mixed adsorption layer on a mercury electrode in the systemp-toluidine-polyethyleneglycol-1M NaClO4

Summary The properties of the mixed adsorption layer on a mercury electrode in the system 1M NaClO₄-p-toluidine-polyethyleneglycol (average molecular masses of polyethyleneglycols: 400 or 10000) are discussed. The parameters of theFrumkin and virial isotherms were determined in the range of strong adsorption potentials. In the range of more negative potentials, a mixed adsorption layer was found by investigating the kinetics of the reduction of Zn(II) ion as a pilot ion. Depending on the concentration ratio of the studied organic substances, inhibition, acceleration, or compensation of both with respect to Zn(II) electroreduction was observed. In the presence of polyethyleneglycol, the efficiency of the Zn(II) ion electroreduction increases due to a greater adsorption lability ofp-toluidine molecules on the mercury surface.

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Untersuchung der gemischten Adsorptionsschicht an einer Quecksilberelektrode im Systemp-Toluidin-Polyethyleneglycol-1M NaClO₄

Zusammenfassung Die Eigenschaften der gemischten Adsorptionsschicht an einer Quecksilberelektrode trode im System 1M NaClO₄-p-Toluidin-Polyethyleneglycol(durchschnittliche Molmassen der Polyethylenglycole: 400 bzw. 1000) werden diskutiert. Die Parameter derFrumkin- und Virialisotherme wurden im Bereich hoher Adsorptionspotentiale bestimmt. Im Bereich negativerer Potentiale wurde durch Untersuchung der Kinetik der Elektroreduktion von Zn(II)-Ionen als Pilotionen eine gemischte Adsorptionsschicht gefunden. In Abhängigkeit von der Konzentration der organischen Verbindungen beobachtet man bezüglich der Elektroreduktion von Zn(II) Hemmung, Beschleunigung oder eine gegenseitige Kompensation beider Effekte. In Gegenwart von Polyethyleneglycol nimmt die Effizienz der Elektroreduktion von Zn(II) aufgrund einer höheren Adsorptionslabilität derp-Toluidin-Moleküle an der Quecksilberoberfläche zu.

     

Suzuki–Miyaura coupling catalyzed by palladium nanoparticles biosynthesized using Glycyrrhiza glabra as reducing and stabilyzing agent

An unprecedented environmentally friendly method has been developed for the synthesis of palladium nanoparticles supported on Glycyrrhiza glabra. The synthesized nanoparticles were utilized in Suzuki–Miyaura reaction between different aryl halides and aryl bronic acid in aqueous media. This heterogeneous catalyst can be reused and recycled repeatedly more than five times with only slight loss of its initial catalytic efficiency. This reaction carrid out under atmospheric pressure with high efficiency, unique and simple work‐up procedure and excellent yields.     

Photoinduced,Direct C(sp2)−H Bond Azo Coupling of Imidazoheteroarenes and Imidazoanilines with Aryl Diazonium Salts Catalyzed by Eosin Y

Herein, a greener approach to the eosin Y-Na₂ catalyzed, C(sp²)−H bond azo coupling of imidazoheteroarene with aryl diazonium salts is described, under acid free conditions. This direct photoredox process resulted in the corresponding azo products in good to excellent yields. Besides, this new approach could also be applicable to anilines, which is a poorly reactive substrate by other methods. The main features of this reaction are that it provides high yields and is gram-scalable and applicable to biologically relevant imidazoheteroarenes and -anilines.     

Biotransformation of two furanocoumarins by the fungi species Aspergillus sp. PTCC 5266 and Aspergillus niger PTCC 5010

The microbial transformations of peucedanin and oreoselon by the fungi Aspergillus niger and Aspergillus sp. were investigated for the first time. Incubation of peucedanin with A. niger yielded a new hydroxylated metabolite with high yield (56%), which was characterized as 2-(1-hydroxypropan-2-yl)-3-methoxy-7H-furo[3,2-g]chromen-7-one. Oreoselon was converted to a new reduced metabolite methyl 3-(2,3-dihydro-6-hydroxy-2-isopropyl-3-oxobenzofuran-5-yl)propanoate in biotransformation by Aspergillus sp. The structures of the metabolites were determined by spectroscopic methods including IR, EI-MS, ¹H NMR, ¹³C NMR, and elemental analysis.     

Triterpenoid saponin from the bark of Guaiacum officinale L

A new triterpenoid saponin, guaianin R (1) was isolated from the n-BuOH extract of bark of Guaiacum officinale L. It was characterized as akebonic acid-3-O-[alpha-L-rhamnopyranosyl-(1 --> 3)-beta-D-glucopyranosyl-(1 --> 3)-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranoside]-28-O-[beta-D-glucopyranosyl]-ester. The structure was established with the help of a comparative study of 1D and 2D 1H- 13C NMR methods. A number of other saponins were isolated and reported from the same species.     

New porphyrins: synthesis,characterization, and computational studies

Molecular Diversity - New trans-A2B2-porphyrins substituted at phenyl positions were synthesized from 4-methylphthalic acid as a starting material through sequential multistep reactions. These...