An efficient method for the synthesis of quinoxaline derivatives catalyzed by titanium silicate-1

Research on Chemical Intermediates - A series of quinoxaline derivatives were efficiently synthesized by convenient and simple procedure in excellent yields using 1 wt.% of titanium silicate (TS-1)...     

Kinetics of catalyzed esterification of acetic acid with n-butanol using carbonized agro-waste

The objective of this research work was to investigate the kinetics of esterification of acetic acid with n-butanol through the variation of experimental parameters. The reaction mixture was catalyzed heterogeneously by a sulfonated catalyst in batch mode of operation. The catalyst was prepared from abundantly available agro-waste, Cajanus cajan husk by chemical activation process, which produces a carbon-based solid catalyst with high surface area. The catalyst was characterized by a Brunauer-Emmet-Teller surface analyzer and Fourier transform infrared spectroscopy to know the surface morphology. Process parameters such as contact time, reaction temperature, and catalyst loading, which can influence the extent of conversion of reactants, were studied. Furthermore, the kinetic investigation was also carried out to estimate the kinetic parameters for uncatalyzed and catalyzed reaction using the second-order pseudo-homogeneous (P-H), Eley-Rideal (E-R), and Langmuir-Hinshelwood (LH) kinetic models for this research work. The kinetic parameters such as activation energy, preexponential factor, and the thermodynamic parameters such as enthalpy and entropy were estimated for uncatalyzed and catalyzed reactions using these three models. The process conditions were optimized for catalyzed and uncatalyzed reactions to obtain the maximum product yield by minimizing root mean square error of each experimental data using the MS-excel solver tool. Thus, this study reveals the high potential of an agro-waste, Cajanus cajan husk as raw material for the synthesis of catalyst. The results show that the E-R model is more appropriate for predicting the dynamic data of an esterification reaction, as the forward rate of reaction estimated using the E-R model are more modified than P-H and L-H models.     

Gold-Catalyzed Oxidative Aminocyclizations of Propargyl Alcohols and Propargyl Amines to Form Two Distinct Azacyclic Products: Carbene Formation versus a 3,3-Sigmatropic Shift of an Initial Intermediate

Gold-catalyzed oxidations of propargyl alcohols with nitrones by using a P(tBu)₂(o-biphenyl)Au⁺ catalyst, afforded bicyclic annulation products from the Mannich reactions of gold enolates. The same reactions of propargyl amines with nitrones by using the same gold catalyst gave distinct oxoarylation products. Our DFT calculations indicate that oxidation of propargyl alcohols with nitrones by using electron-rich gold catalysts lead only to gold carbenes, which can generate gold enolates or oxoarylation intermediates with enolate species having a barrier smaller than that of oxoarylation species.     

[HDBU][HSO4]-catalyzed facile synthesis of new 1,2,3-triazole-tethered 2,3-dihydroquinazolin-4[1H]-one derivatives and their DPPH radical scavenging activity

Research on Chemical Intermediates - A simple and efficient protocol has been developed for the synthesis of new1,2,3-triazole-2,3-dihydroquinazolin-4[1H]-one (DHQ) conjugates(6a?j) via...     

Calotropis procera extract induces apoptosis and cell cycle arrest at G2/M phase in human skin melanoma (SK-MEL-2) cells

Calotropis procera (family: Asclepiadaceae) contains cardiac glycosides which are cytotoxic to cancer cells. The extracts of C. procera have been reported to be cytotoxic to many cancer cell lines and this is the first report against the human skin melanoma cells (SK-MEL-2). The SK-MEL-2 cells treated with C. procera methanolic extract (CPME) were analysed for growth inhibition and apoptosis. The exposure of phosphatidylserine in apoptotic SK-MEL-2 was analysed by using the Annexin-V FITC flow cytometry method. In CPME-treated SK-MEL-2 cells, 19.6% of apoptotic and 58.3% dead cells were observed. The 15.97% and 15.85% of early apoptotic cells were found at 20 μg/mL of the ouabain and paclitaxel, respectively. Active caspases, nuclear degradation confirmed apoptotic SK-MEL-2 cells in time- and dose-dependent manner. The cell cycle analysis shows that CPME treated cells halt at G2/M phase. Significant cytotoxic activity of CPME against SK-MEL-2 may be attributed to its high cardenolide content.     

A New Approach for the Synthesis of Miktoarm Star Polymers Through a Combination of Thiol–Epoxy “Click” Chemistry and ATRP/Ring‐Opening Polymerization Techniques

A new approach was developed for synthesis of certain A₃B₃‐type of double hydrophilic or amphiphilic miktoarm star polymers using a combination of “grafting onto” and “grafting from” methods. To achieve the synthesis of desired miktoarm star polymers, acetyl protected poly(ethylene glycol) (PEG) thiols (M_n = 550 and 2000 g mol^?1) were utilized to generate A₃‐type of homoarm star polymers through an in situ protective group removal and a subsequent thiol–epoxy “click” reaction with a tris‐epoxide core viz. 1,1,1‐tris(4‐hydroxyphenyl)ethane triglycidyl ether. The secondary hydroxyl groups generated adjacent to the core upon the thiol–epoxy reaction were esterified with α‐bromoisobutyryl bromide to install atom transfer radical polymerization (ATRP) initiating sites. ATRP of N‐isopropylacrylamide (NIPAM) using the three‐arm star PEG polymer fitted with ATRP initiating sites adjacent to the core afforded A₃B₃‐type of double hydrophilic (PEG)₃[poly(N‐isopropylacrylamide)] (PNIPAM)₃ miktoarm star polymers. Furthermore, the generated hydroxyl groups were directly used as initiator for ring‐opening polymerization of ε‐caprolactone to prepare A₃B₃‐type of amphiphilic (PEG)₃[poly(ε‐caprolactone)]₃ miktoarm star polymers. The double hydrophilic (PEG)₃(PNIPAM)₃ miktoarm star polymers showed lower critical solution temperature around 34 °C. The preliminary transmission electron microscopy analysis indicated formation of self‐assembly of (PEG)₃(PNIPAM)₃ miktoarm star polymer in aqueous solution. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 146–156     

Effectiveness of radiation processing in elimination of Campylobacter from poultry meat

Campylobacter, a common poultry intestine commensal, is a well known cause of human gastric illnesses across the globe. Consumption of contaminated poultry meat is a major cause of Campylobacter related infections. In the present study, radiation sensitivity of indigenous strains of C. jejuni and C. coli isolated from poultry was evaluated. The decimal reduction dose (D₁₀) values of different Campylobacter isolates at 0-4 °C in saline and blood broth were in the range of 0.120-0.210 kGy and 0.170-0.234 kGy, respectively. D₁₀ values in chicken meat homogenate for Campylobacter were in the range of 0.110-0.190 kGy. Chicken meat samples were inoculated with C. jejuni and exposed to gamma radiation to study the effectiveness of radiation treatment in elimination of Campylobacter. Radiation treatment with a dose of 1 kGy could achieve complete elimination of 10⁵ CFU of Campylobacter/g in poultry meat samples. No recovery of Campylobacter was observed, even after enrichment and selective plating in 1 kGy treated chicken meat samples stored at 4 °C up to 7 days. Present study shows that irradiation of poultry meat with 1 kGy can ensure safety of poultry meat.