A Facile and Efficient One‐Pot Electrochemical Synthesis of Thiazole Derivatives in Aqueous Solution

In the present work, the electrooxidation of hydroquinones 1a and 1b , and catechols 1c and 1d was studied in the presence of rhodanine ( 3 ) as nucleophile in a mixture of EtOH and phosphate buffer solution as ‘green’ media using cyclic voltammetry and controlled‐potential coulometry. The results indicated that the corresponding p‐ and o‐quinones formed from the hydroquinones and catechols, respectively, participate in Michael addition reaction to yield new thiazole derivatives. The electrochemical syntheses of these new thiazole derivatives were performed successfully at three graphite rod electrodes in undivided cells in good‐to‐excellent yields at room temperature without any catalyst.     

Chelator-free radiolabeling of dextran with 68Ga for PET studies

Journal of Radioanalytical and Nuclear Chemistry - The possibility of 68Ga-dextran complex formation was analyzed in an HEPES-buffered (pH = 4.5) as well as in an alkaline...     

Determination of lewisite metabolite 2-chlorovinylarsonous acid in urine by use of dispersive derivatization liquid-liquid microextraction followed by gas chromatography–mass spectrometry

The purpose of this study was to develop a sensitive and simple method, based on dispersive derivatization liquid-liquid microextraction–gas chromatography–mass spectrometry (DDLLME–GC–MS) in scanning and selected-ion-monitoring (SIM) modes, for detection of 2-chlorovinylarsonous acid (CVAA) as a hydrolysis product and urinary metabolite of lewisite in urine samples. Chloroform (65 μL), methanol (500 μL), and ethanedithiol (10 μL) were used as extraction solvent, dispersive solvent, and derivatizing reagent, respectively. Critical conditions of the proposed method were optimized. The nucleophilic reactions of dithiol and monothiol compounds with CVAA were also studied using a competitive method. In view of the high affinity of trivalent arsenic for sulfhydryl groups, the interaction between CVAA and bis(2-chlorovinyl)arsonous acid (BCVAA) and free cysteine (Cys) was also investigated using liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS). The interference of Cys, present in human urine, with the detection of CVAA was evaluated using dithiol and monothiol chemicals as derivatization agents. The developed method provided a preconcentration factor of 250, and limits of detection of 0.015 and 0.30 μg L^?1 in SIM and scanning modes, respectively. The calibration curves were linear over the concentration range of 1–400 μg L^?1 in full-scan mode. The relative standard deviation (RSD) values were calculated to be 5.5 and 3.2 % at concentrations of 20 and 100 μg L^?1, respectively. Collision-induced dissociation studies of the major electron-impact (EI) ions were performed to confirm the proposed fragment structure of CVAA-dithiols derivatives. Results indicated that the developed method for analysis of CVAA is suitable not only for verification of human exposure to lewisite, but also for quantification of CVAA in urine samples.

Electrosynthesis of hydroquinonethioethers using electrochemical oxidation of hydroquinone in the presence of thiouracil derivatives

Electrochemical oxidation of hydroquinone(1a) has been studied in the presence of 6-methyl-2-thiouracil(3a) and 6-propyl-2-thiouracil(3b) as nucleophiles in a DMF/buffer mixture,using cyclic voltammetry and controlled-potential coulometry.The results indicated that the p-quinone(2a) derived from 1a participates in a 1 4-Michael addition reaction with the thiouracil derivatives(3a–b) to form the corresponding hydroquinonethioether derivatives(6a–6b).The electrosynthesis of these compounds(6a–b) has been successfully performed on carbon rod electrodes in an undivided cell in good yield and purity.     

Facile and one-pot,electro-organic synthesis of a new bis-quinone by the ECCE mechanism in green media

Electrochemical oxidation of 4-methyl catechol(1a) is investigated in the presence of 1,3-indandione(3)as nucleophile in phosphate buffer solution(0.2 mol/L,pH 6) mixed with ethanol as organic green solvent(50/50) using cyclic voltammetry and controlled-potential coulometry.The results indicated thatquinones derived from electro-oxidation of 1a,participated in a 1,4-Michael addition reaction with1,3-indandione(3) under ECCE mechanism.In this direction,a new bis-quinone was synthesized in high yield and good purity using a facile and convenient electrochemical pathway by carbon anode electrodes in an undivided cell.     

Silica‐supported synthesis of some 1,3,5‐trisubstituted 2‐pyrazolines under solvent‐free and microwave irradiation conditions

A simple method for the synthesis of 2‐pyrazolines is described which occurs on silica surface under solvent‐free conditions within 110‐180 sec using microwave irradiation. The results obtained indicate that the use of silica gel as a support in pyrazoline formation reactions can have a profound effect on reaction rates and yields and cause cleaner reaction conditions.     

An efficient conversion of catechols into 6H‐benzofuro[3,2‐c][1]‐benzopyran‐6‐one derivatives

Coupling of in‐situ generated o‐benzoquinones with 4‐hydroxycoumarin as a nucleophile has been studied in the presence of potassium ferricyanide as an oxidizing agent in aqueous solution. The results indicate that the quinones derived from catechols, participate in Michael addition reactions with 4‐hydroxycoumarin to form the 6H‐benzofuro[3,2‐c][1]benzopyran‐6‐one derivatives.     

A green and efficient synthesis of isoxazol-5(4<Emphasis Type="Italic">H</Emphasis>)-one derivatives in water and a DFT study

A series of 4-arylmethylene-3-methylisoxazol-5(4H)-one derivatives are obtained via treating ethyl acetoacetate, hydroxylamine hydrochloride and variety of aromatic aldehyde compounds in the presence of antimony trichloride as an efficient catalyst in aqueous media. Mild conditions, safe, short reaction times, commercially available catalyst, environmentally friendly, no uses of organic solvent and high yields are remarkable advantages to this process. (Z)-4-(3-hydroxybenzylidene)-3-methylisoxazol-5(4H)-one, (HBIM), is characterized by theoretical (density functional theory) and experimental (IR, ¹H NMR, CV and UV). The structural parameters, vibrational frequencies, molecular electrostatic potential, frontier molecular orbital analysis (HOMO–LUMO), thermodynamic properties and nonlinear optical properties are found and discussed. UV–Vis spectra are recorded in two organic solvents. Thermal stability of HBIM is studied by thermogravimetric analysis. The molecule orbital contributions are studied using the total and partial density of states (TDOS and PDOS).