Three-component one-pot synthesis of quinoline–furan conjugates from acetylenedicarboxylate,isocyanide, and 2-chloroquinoline-3-carbaldehyde

We have developed a facile and efficient method for the synthesis of functionalized novel furylquinolines. A variety of quinoline–furan conjugates were obtained via the condensation of 2-chloroquinoline-3-carbaldehyde with acetylenecarboxylates and isocyanides in good to excellent yields.     

Immobilization of nickel ions onto the magnetic nanocomposite based on cross‐linked melamine groups: Effective heterogeneous catalyst for N‐Arylation of Arylboronic acids

A new magnetic heterogeneous catalyst was synthesized by immobilization of nickel ions onto a cross‐linked polymeric nanocomposite composed of cyanuric chloride, ethylenediamine and functionalized magnetic nanoparticles. The resulting nitrogen rich support was capable of adsorbing large amounts of nickel ions (1.20 mmol g^?1). The synthesized catalyst was characterized using AAS, TEM, FT‐IR, EDX, TGA, SEM, BET and XRD techniques. The performance of the prepared catalyst was investigated in the C‐N coupling of arylamines with aryl boronic acids. The reaction was carried out under a mild condition and good to moderate to good yields of products was obtained using only 5.0 mol% of the catalyst. The catalyst was easily recovered and reused for at least 7 times without any significant loss of its activity.     

Biotransformation of two furanocoumarins by the fungi species Aspergillus sp. PTCC 5266 and Aspergillus niger PTCC 5010

The microbial transformations of peucedanin and oreoselon by the fungi Aspergillus niger and Aspergillus sp. were investigated for the first time. Incubation of peucedanin with A. niger yielded a new hydroxylated metabolite with high yield (56%), which was characterized as 2-(1-hydroxypropan-2-yl)-3-methoxy-7H-furo[3,2-g]chromen-7-one. Oreoselon was converted to a new reduced metabolite methyl 3-(2,3-dihydro-6-hydroxy-2-isopropyl-3-oxobenzofuran-5-yl)propanoate in biotransformation by Aspergillus sp. The structures of the metabolites were determined by spectroscopic methods including IR, EI-MS, ¹H NMR, ¹³C NMR, and elemental analysis.     

Electron delocalization and aromaticity variations in the stacked nucleic acid base pairs

A newly developed exchange-correlation functional (MPWB1K) in density functional theory has been applied to evaluate the electron delocalization of individual fragments in the stacking interaction between nucleic acid bases (NABs). Electronically and structural-based indices have been employed to investigate the aromaticity variation during stacking interaction. A quantitative study of NABs in their isolated and stacked forms reveals that stacking interaction causes a decrease in bond delocalization. It is shown that the decrease in the aromaticity is accompanied by local decrease in two-center delocalization indices within the pyrimidine rings. We found that the aromaticity exhibits a similar trend for NABs in both their isolated and stacked forms. Moreover, it is indicated that aromatic fluctuation index is more sensible index to delineate the aromaticity variation during stacking interaction.

     

Rings consisting entirely of certain elements

We completely determine when a ring consists entirely of weak idempotents, units and nilpotents. We prove that such ring is exactly isomorphic to one of the following: a Boolean ring; Z₃ ⊕ Z₃; Z₃ ⊕ B where B is a Boolean ring; local ring with nil Jacobson radical; M₂(Z₂) or M₂(Z₃); or the ring of a Morita context with zero pairings where the underlying rings are Z₂ or Z₃.     

Theoretical study of Diels-Alder reaction: Role of substituent in regioselectivity and aromaticity

A comparative study on the influence of the substituents on the Diels-Alder reaction was performed. The energy profiles for 11 sets of Diels-Alder reaction between monosubstituted derivatives of butadiene and ethylene have been studied and the structures of all transition states were located at B3LYP/6-31+G* level. Four pathways were independently investigated; the reaction between substituted ethylene and 1-substituted butadiene leading to ortho (a ₁) and meta (a ₂) adducts, and in the same manner, the reaction between substituted ethylene and 2-substituted butadiene yields para (b ₁) and meta (b ₂) adducts. Inspection of both the activation barriers and the reaction energies for 44 reactions revealed that the pathway b ₁ is both thermodynamically and kinetically more favorable in all types of Diels-Alder reactions; while the pathway a ₁ can be labeled only as kinetic pathway. The aromaticity of all 44 transition state structures was measured using para delocalization index to study the effect of aromaticity on the reaction path. The calculations suggest that in normal and neutral DA reactions there is a gain in aromatic stabilization of the transition state which reduces slightly the activation barrier of the kinetic pathway a ₁.     

Synthesis and characterization of new 13 and 14-membered macrocycles and their transition metal complexes

Two new macrocyclic ligands 1,4,7,9,12-pentaaza-10,11-dioxo-8,9,12,13-bis-(1-oxo-3-thio-2-hydropyrimidine)-trideca-7,13-diene, (L¹) and 1,4,7,9,12-pentaaza-10,12-dioxo-8,9,13,14-bis-(1-oxo-3-thio-2-hydropyrimidine)-tetradeca-7,14-diene, (L²) and their complexes with Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II and Zn^II have been synthesized, and characterized by elemental analysis, i.r., ¹H-n.m.r., e.p.r., u.v.–vis. spectroscopy, magnetic susceptibility and conductance measurements. The conductivity measurements suggest that the complexes of divalent metal ions are 1:1 electrolytes whereas the trivalent metal ions are non-electrolytes. On the basis of electronic spectra and magnetic moment measurements the Cr^III and Fe^III complexes are octahedral, while the divalent metal complexes are tetrahedral except for the Ni^II and Cu^II complexes which are proposed to have square planar geometry. All the ligands and their complexes have been screened against gram-positive bacteria Staphylococcus aureus and gram-negative bacteria E. coli. The results show that they inhibit the growth of bacteria.     

An enzymatic flow analysis method for the determination of phosphatidylcholine in sediment pore waters and extracts

A sensitive and selective flow injection method for the determination of phosphatidylcholine (PC) in sediment pore waters and extracts is described. It involves the use of phospholipase C, alkaline phosphatase and choline oxidase co-immobilized on controlled pore glass in a packed column reactor. The final product of the enzymatic reaction of phosphatidylcholine is hydrogen peroxide, and this is detected by measuring the chemiluminescence emission resulting from cobalt(II) catalysed reaction with luminol. The flow injection method is rapid (30 injections/h), reproducible (1.4% R.S.D. at 3 μM PC, n = 10) with a detection limit of 0.14 μM (estimated from 3σ_n−1 of the measured blank). A linear calibration response was obtained over a concentration range of 0.5-9 μM (r = 0.999). The method has been applied to the determination of phosphatidylcholine in sediment extracts and sediment pore waters.