Yb(OTf)3 Catalyzed Synthesis, Antimicrobial and Insecticidal activity of some Biscoumarins

Published ArticleIn the present study, we report Yb(OTf)3 catalyzed synthesis of biscoumarins by pseudo three-component reaction of aldehyde and 4-hydroxycoumarin. The synthesized biscoumarins were evaluated for antimicrobial and insecticidal activity. Results of antimicrobial activity were found to be moderate to good in terms of zones of inhibition and MIC values against E. coli, P. vulgaris and S. aureus. The compounds were inactive against the used fungal strains except B4 in case of Penicillium. Insecticidal activity of the biscoumarins B-1, B-3, B-5 and B-11 was found to be good exhibiting 70-75% mortality effect on Callosobruchus maculatus

An efficient naphthalimide based receptor for selective detection of Hg2+and Pb2+ions

Naphthalimide based receptor 1 with N-substituted benzothiazole and pyrrolidine subunit is designed, synthesized, and characterized using FT-IR,1H and 13C NMR spectroscopy and mass spectrometry techniques. The receptor 1 exhibits prominent optical response for Hg2+and Pb2+ions allowing the detection of these ions in acetonitrile (ACN). The formation of the receptor 1:cation complexes have been investigated using UV-Vis and fluorescence emission titration. Further, the selectivity of the receptor 1towards Hg2+and Pb2+ ions on the presence of various interfering cations such as Mg2+, Ba2+, Ni2+, Co2+, Cu2+, Ag2+, Fe2+, Fe3+and Cr3+ has been confirmed by UV-Vis and fluorescence spectroscopy. The binding constant between receptor 1 and Hg2+ and Pb2+ was estimated by Benesi-Hildebrand plot and equations. The binding constants have been found to be Ka= 3.43286 ´ 10−6 and Ka= 2.84079 ´ 10−6 M for Hg2+ and Pb2+, respectively. The limit of detection (LOD) for Hg2+and Pb2+by receptor 1are down to 7.44 ´ 10−10 M and 1.26 ´ 10−9 M, respectively. In addition, Job’s plot analysis reveals 1:2 binding stoichiometry between the receptor 1 and Pb2+ and Hg2+ cations.

L-Pyrrolidine-2-Carboxylic Acid Sulfate: A New Ionic Liquid for the Synthesis of Bioactive Tetrahydrobenzo[b]pyrans

Published ArticleMulticomponent reactions (MCRs), a significant subclass of reac tions, are one-pot processes in which three or four easily-approachable components react to form a single product. The methodology is a powerful synthetic tool for the preparation of important drugs and other biologically active compounds. 1 MCRs have been useful in the development of environ- mentally-friendly and less expensive procedure s for the generation of libraries of heterocy- clic compounds 2 and the development of MCRs can le ad to new, efficient, synthetic methodologies. Tetrahydrobenzo[b]pyrans an d their derivatives are an important class of heterocyclic compounds with antic oagulant, antitumor, spasmoly tic, antibacterial, diuretic, potassium channel activating and insulin-sensitizing activities. 3–6 4H-Benzo[b]pyrans are usually synthesized from a -cyano cinnamonitrile derivatives with dimedone catalyzed by acid or base. 7 Recently MCRs have been used for their preparation. As compared to the conventional linear step synthesis, they can make the process easier, reduce time, save money, energy, and raw materials, resulting in both economic and environmental bene- fits. 8–9 A number of methods have been reported using dimedone, aromatic aldehydes and malononitrile in the presence of catalysts, such as CeCl 3 ¢ 7H 2 O, 10 N-methylimidazole, 11 tet- ramethyl ammonium hydroxide, 12 MgO, 13 amines, 14 2,2,2-trifluoroethanol, 15 and TiO 2 . 16 Other methods have involved microwave heating, 17 ultrasonic irradiation, 18 electrosynthe- sis, 19 hexadecyldimethylbenzylammonium bromide (HDMBAB), 20 Na 2 SeO 4 , 21 DABCO, 2

Microwave Assisted Synthesis of 2,4-Diphenyl-4H-chromen-5-one Using ZnCl2/Montmorillonite K-10

α, β-Unsaturated carbonyl compounds and 1, 3-cyclohexanedione under microwave irradiation in the presence ZnCl2/montmorillonite K-10 offers the corresponding 2,4-diphenyl-4H-chromen-5-one in excellent yield. Catalyst is recycled and reused for several time

Nano-ZnO Catalyzed Green and Efficient One-Pot Four-Component Synthesis of Pyranopyrazoles

An efficient zinc oxide nanoparticle catalyzed one-pot, four-component synthesis of 6-amino-3-methyl-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles from aromatic aldehyde, malononitrile, ethyl acetoacetate, and hydrazine hydrate in aqueous medium is described. Since water was employed as the reaction medium, it serves as a green route for the synthesis of pyrano[2,3-c]pyrazoles. The advantages associated with the present protocol include nonchromatographic purification technique, use of recyclable heterogeneous nano-ZnO catalyst in aqueous medium, and short reaction time. It combines successfully the synergistic effect of green chemistry with nanocatalysis

Spinel zinc ferrite nanoparticles: an active nanocatalyst for microwave irradiated solvent free synthesis of chalcones

A profoundly effective magnetically recoverable nano zinc ferrite nanocatalyst was fabricated by means of sol-gel auto ignition strategy. The synthesized nanocatalyst has been completely portrayed by standard techniques for structural, morphological, compositional, surface, magnetic, dielectric, optical and photoluminescence properties individually. The x-ray diffraction pattern affirmed the arrangement of cubic spinel structure with an average crystallite size of 21 nm. FE-SEM images uncovered the circular morphology with nanometric average grain measure (37 nm). The surface area, pore volume and pore radius was observed to be 39.812 m ^2 g ^−1 , 3.41 cc g ^−1 and 1.34 nm individually from BET analysis. VSM investigation demonstrated the superparamgnetic nature of the prepared sample with moderate magnetization value and negligible coercivity. The optical band gap deduced from UV–vis spectra was observed to be 2.098 eV. Every one of these properties of zinc nanoferrite makes them brilliant contender for microwave radiation absorption. Further, a proficient and versatile microwave irradiated solvent free synthesis of chalcone derivatives has been developed using prepared zinc nanoferrite catalyst. The remarkable highlights of this new protocol are solvent free reaction, economical cheapness, eco-friendliness, high yields, reduced reaction times and easy recovery and reuse of zinc ferrite nanocatalyst

Proton Triggered Colorimetric and Fluorescence Response of a Novel Quinoxaline Compromising a Donor-Acceptor System

Quinoxaline-based novel acid-responsive probe Q1 was designed on the basis of a conjugated donor-acceptor (D-A) subunit. Q1 shows colorimetric and fluorometric changes through protonation and deprotonation in dichloromethane. With the addition of the trifluoroacetic acid (TFA), UV-vis absorption spectral changes in peak intensity of Q1 was observed. Moreover, the appearance of a new peaks at 284 nm 434 nm in absorption spectra with the addition of TFA indicating protonation of quinoxaline nitrogen and form Q1.H+ and Q1.2H+. The emission spectra display appearance of new emission peak at 515 nm. The optical property variations were supported by time resolved fluorescence studies. The energy band gap was calculated by employing cyclic voltammetry and density functional calculations. Upon addition of triethylamine (TEA) the fluorescence emission spectral changes of Q1 are found to be reversible. Q1 shows color changes from blue to green in basic and acidic medium, respectively. The paper strip test was developed for making Q1 a colorimetric and fluorometric indicator

A Naphthalimide-Benzothiazole Conjugate as Colorimetric and Fluorescent Sensor for Selective Trinitrophenol Detection

Although chemical structural modification of naphthalimides is widely employed for the purpose of sensing explosives, the effects of such modification have been little explored. Herein, we report the design and synthesis of a new naphthalimide-benzothiazole conjugate (1) and its ability to sense various nitrophenols by means of its colorimetric and fluorescent characteristics. Under long-range UV light (365 nm), 1 displayed a color change of its solution from bluish to colorless only upon addition of 2,4,6-trinitrophenol (TNP). Photoluminescence spectroscopy showed quantitative fluorescence quenching by TNP of the emission peaks of 1 at 398 nm and 418 nm due to donor–acceptor electron transfer. The interaction of 1 with TNP was via a cooperative, non-covalent hydrogen-bonding interaction. Receptor 1 exhibited high sensitivity and selectivity towards TNP over various aromatic nitro analytes. The binding constant (K) and Stern–Volmer constant (Ksv) between 1 and TNP were found to be 5.332 × 10−5 M and 2.271 × 106 M−1, respectively. Furthermore, the limit of detection was calculated and found to be as low as 1.613 × 10−10 M