Preparation of Silica‐bonded Propyl‐diethylene‐triamine‐N‐sulfamic Acid as a Recyclable Catalyst for Chemoselective Synthesis of 1,1‐Diacetates

A simple and efficient procedure for the preparation of silica‐bonded propyl‐diethylene‐triamine‐N‐sulfamic acid (SPDTSA) by reaction of 3‐diethylenetriamine‐propylsilica (DTPS) and chlorosulfonic acid in chloroform is described. Silica‐bonded propyl‐diethylene‐triamine‐N‐sulfamic acid is employed as a recyclable catalyst for the synthesis of 1,1‐diacetates from aromatic aldehydes and acetic anhydride under mild and solvent‐free conditions at room temperature. Catalyst could be recycled for several times without any additional treatment.     

Attack of radicals and protons on ladderane lipids: quantum chemical calculations and biological implications

Quantum chemical calculations on possible decomposition processes for ladderane lipids are described. Based on the results of these calculations, it is proposed that hydrogen atom abstraction next to the ladderane core can lead to opening of the cyclobutane rings comprising the ladderane substructure, and protonation leads directly to fragmentation. Potential biological implications of these processes are discussed.     

Research on the BET Surface Area and Packing of Molecules on the Activated Carbon

Adsorption of different aromatic compounds (two of them are electrolytes) onto an untreated activated carbon (F100) is investigated. The experimental isotherms are fitted into Langmuir homogenous and heterogeneous Model. Theoretical maximum adsorption capacities that are based on the BET surface area of the adsorbent cannot be close to the real value. The affinity and the heterogeneity of the adsorption system observed to be related to the pK_a of the solutes. The maximum adsorption capacity (Q _max) of activated carbon for each solute dependent on the molecular area as well as the type of functional group attached on the aromatic compound and also pH of solution. The arrangement of the molecules on the carbon surface is not face down. Furthermore, it is illustrated that the packing arrangement is most likely edge to face (sorbate-sorbent) with various tilt angles.For characterization of the carbon, the N₂ and CO₂ adsorption were used. X-ray Photoelectron Spectroscopy (XPS) measurement was used to surface elemental analysis of activated carbon.     

Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of strong CH-acids: one-pot synthesis of highly functionalized annulated 4H-pyrans

The highly reactive 1:1 adduct, produced from the reaction between dialkyl acetylenedicarboxylates and alkyl isocyanides, was trapped by strong cyclic CH-acids such as 4-hydroxy-6-methyl-2H-pyran-2-one or 4-hydroxycoumarin to yield dialkyl 2-(alkylamino)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3,4-dicarboxylates or dialkyl 7-methyl-2-(alkylamino)-5-oxo-4H,5H-pyrano[4,3-b]pyran-3,4-dicarboxylates in good yields at room temperature.     

The reaction of (N-isocyanimino)triphenylphosphorane with dialkyl acetylenedicarboxylates in the presence of 1,3-diphenyl-1,3-propanedione: a novel three-component reaction for the stereoselective synthesis of dialkyl (Z)-2-(5,7-diphenyl-1,3,4-oxadiazepin-2-yl)-2-butenedioates

Reactions of dialkyl acetylenedicarboxylates with (N-isocyanimino)triphenylphosphorane in the presence of 1,3-diphenyl-1,3-propanedione proceed smoothly at room temperature to afford dialkyl (Z)-2-(5,7-diphenyl-1,3,4-oxadiazepin-2-yl)-2-butenedioates in high yields. The stereochemistry of the final products were confirmed by single crystal X-ray structure determination. The reaction is completely stereoselective.     

Chemical constituents and antioxidant activity of essential oil and organic extract from the peel and kernel parts of Citrus japonica Thunb. (kumquat) from Iran

The constituents of essential oils and organic extracts from peel and kernels of Citrus japonica were analysed by GC and GC/MS. The content of essential oil in peel and kernel was 1.1 and 0.8% based on dry weight. The essential oil of C. japonica peel and kernel was characterised by a higher amount of limonene (51.0 and 47.1%) and germacrene D (12.1 and 6.3%), and the hexane extracts of its peel and kernel were characterised by a higher amount of dodecanol-1(12.9 and 20.8%) and linolenic acid (13.1 and 16.3%), respectively. The antioxidant activities of oils were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. The results indicate that both oils from different parts of C. japonica possess considerable antioxidant activity. The fruit peel and kernel essential oil could thus be useful in the industries, chiefly in the food and pharmaceutical industries.     

Development of a green miniaturized quick,easy, cheap,effective, rugged,and safe approach in tandem with temperature-assisted solidification of floating menthol droplet for analysis of multiclass pesticide residues in milk

A new green miniaturized quick, easy, cheap, effective, rugged, and safe approach was developed and used for the extraction of multiclass 16 pesticides in milk before gas chromatography analysis. The miniaturization of method reduced the consumption of chemical reagents and samples. Magnetic three-dimensional graphene was used as sorbent in the clean-up step. Choline chloride:lactic acid (1:2) natural deep eutectic solvent was used as desorption solvent. Temperature-assisted solidification of floating menthol drop was executed for preconcentration of analytes. The method parameters including sorbent, desorption solvent, sorption and desorption times, menthol amount, pH, and ionic strength were optimized. The limit of quantification and linear range were 0.03–0.38 and 0.03–250 μg/kg, respectively. The accuracy was assessed by recovery evaluation at the spike levels of 50 and 100 μg/kg, in the range of 61–119%, with relative standard deviations within 2.1–18.2%. The method was applied to the analysis of pasteurized low and high-fat bovine milk, and various pesticide residues were detected in the concentrations range of 1.24–4.68 μg/kg. Finally, the greenness of the procedure was evaluated using the Analytical Eco-Scale. This work represents the first application of hybrid miniaturized extraction/preconcentration using a natural deep eutectic solvent and menthol to analyze pesticides.     

A facile and convenient synthesis of tetrasubstituted N‐hydroxypyrroles via intramolecular wittig reaction

Treatment of triphenylphosphine with dialkyl acetylenedicarboxylate leads to 1:1 adduct and concomitant protonation of late adduct by pentan‐2,3,4‐trione 3‐oxime gave the reactive intermediate, vinyltriphenylphosphonium salts, which undergoes an intramolecular Wittig reaction to produce tetrasubstituted N‐hydroxypyrroles in fairly high yields. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:100–103, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20382