Ehsan Ullah Mughal

Tris(tetraceno)triquinacenes: synthesis and photophysical properties of threefold linearly extended tribenzotriquinacenes.

The linear extension of the rigid, C(3v)-symmetrical carbon framework of tribenzotriquinacene (TBTQ) along its three wings is reported. The key step of the extension procedure consists of a Diels-Alder reaction of three ortho-quinodimethane units generated in situ at the triquinacene core. The use of 1,4-naphthoquinone provides a facile and particularly efficient access to tris(tetraceno)-annellated triquinacenes. The steady-state photophysical properties of these new oligotetracenes bearing three mutually orthogonal chomophores are determined and analyzed by DFT calculations.

A FACILE AND CHEAP METHOD FOR THE CONVERSION OF FLAVONES INTO 4-THIOFLAVONES USING PHOSPHORUS PENTASULFIDE AND SODIUM HYDROGEN CARBONATE

A facile, rapid, high yielding and relatively cheaper method has been developed for the synthesis of 4thioflavones by using phosphorus pentasulfide and sodium hydrogen carbonate. Seven new and five known substituted 4-thioflavones prepared by this method are reported Introduction Flavones (2-phenyl-benzo-y-pyrone) are well known naturally occurring polyphenols compounds [1-3]. These have been reported to possess a vast range of biological properties [4-5], However, the corresponding 4-thio analogues of flavones have received less attention due to limited methods available for their preparation, although these sulfurated flavones may offer new and pronounced biological properties. They may also be used as precursors for the synthesis of a variety of other organic compounds. The un-substituted flavones have been transformed into 4thio analogues by several research groups [6-12). For this purpose, phosphorus pentasulfide was used as the thiation agent. In one case [10] this source of sulfur-atom was replaced by silicon disulfide or boron sulfide, but these two reagents proved to be highly sensitive to water. The data available in some other reports about the conversion of substituted flavones into substituted 4-thioflavones via 4,4-dicholorflavenes [11, 13, 15] does not provide information to evaluate the influence of substitution on the thiation of the flavones. Then again an efficient, high yielding and effective procedure [17] was worked out for the preparation of 4-thioflavones by the reaction of flavones with Lawesscpns reagent [18, 19] without affecting the substitution pattern of the starting flavone. This method however requires excess of the reagent (0.5-3.0 molar equiv); the reaction time is lengthy (2-25h) and is conducted in dry non-polar hydrocarbon solvents at elevated temperatures that usually results in generation of side products. For the purification of thioflavones, column chromatography has to be employed. Lawessons reagent is not suitable for flavones having low melting points. This reagent has high water sensitivity, high price and difficult to handle Moreover, the mechanism of this reagent has not been properly proposed. In 1973, Scheeren et al. [20] reported that carbonyl compounds could be converted into the corresponding thiocarbonyls by the use of phosphorus pentasufide and sodium bicarbonate in acetonitrile or ether solvents. However, when we applied this procedure to the un-substituted and substituted flavones, an interesting reaction occurred to give 4-thioflavones with high yield and having no influence on substitution pattern on flavones. We report herein the synthesis of seven new and five known variably substituted thioflavones by this method that is less time consuming, occurs at low temperature and thus no complex side products are generated. This process is very simple, relatively cheaper, easy to handle and offers higher yields.

Biotechnology: A powerful tool for the removal of cadmium from aquatic systems

The prime objective of the present research work was to evaluate the efficiency of bio-machine for the removal of Cadmium (Cd) from aquatic systems. Aspergillus niger fungus was used as bio-machine to remove Cd from aquatic systems. Twenty three different strains (IIB-1 to IIB-23) were isolated from industrial effluents and the Langmuir and Freundlich models were applied to the best Cadmium removal strain IIB-23 in order to obtain the adsorption parameters. Different parameters such as pH, temperatur e, contact time, initial metal concentratio, and biomass dosage on the biosorption of Cd were studied. The percent removal of Cd initially increased with an increase in pH ranging from 5.5-6.5 and then decreased by increasing pH from 7.0-7.5. An optimized pH used for Cd removal from aquatic systems was found to be 6.5. Additionally, an optimum amount of biomass was 1.33 g for the maximum removal of Cd from the aqueous solutions with initial metal concentration of 75 mg/L. The results obtained thus indicated that Langmuir model is the best suited for the removal of Cd from aquatic systems.

Corrigendum to “Synthesis, structure-activity relationship and molecular docking studies of 3- O -flavonol glycosides as cholinesterase inhibitors” [Bioorg. Med. Chem. 26 (12) (2018) 3696–3706]

a Department of Chemistry, University of Gujrat, Gujrat 50700, Pakistan Department of Chemistry, Govt. College Women University, Sialkot 51300, Pakistan c Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan d Department of Chemistry, University of Azad Jammu and Kashmir, Muzaffarabad, Pakistan e Department of Physics, University of Sargodha, Sargodha, Pakistan H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan g Department of Clinical Pharmacy, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, P.O. Box 31441, Dammam, Saudi Arabia