Ligand-free Pd(OAc)(2) was found to catalyze very efficiently the direct arylation of imidazo[1,2-a]pyridines at C3 under very low catalyst concentration. The reaction can be performed employing as little as 0.1-0.01 mol % catalyst with electron-deficient and some electron-excessive aryl bromides.

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In this study, adsorption of dirhamnolipid biosurfactant on a Gram-negative Pseudomonas aeruginosa, two Gram-positive Bacillus subtilis, and a yeast, Candida lipolytica, was investigated, and the causality between the adsorption and change of cell surface hydrophobicity was discussed. The adsorption was not only specific to the microorganisms but also depended on the physiological status of the cells. Components of the biosurfactant with different rhamnosyl number or aliphatic chain length also exhibited slight difference in adsorption manner. The adsorption indeed caused the cell surface hydrophobicity to change regularly; however, the changes depended on both the concentrations of rhamnolipid solutions applied and the adsorbent physiological conditions. Orientation of rhamnolipid monomers on cell surface and micelle deposition are supposed to be the basic means of adsorption to change cell hydrophobicity at low and high rhamnolipid concentrations, respectively. This study proposed the possibility to modify cell surface hydrophobicity with biosurfactant of low concentrations, which may be of importance in in situ soil remediation.

Eight polyoxometalate (POM)-based frameworks were synthesized under hydrothermal conditions, using different octamolybdate isomers (Mo8) and copper-organic fragments or organic units in the presence of different bases. These compounds are named as 7), and [(H 2 bpp) 2 (β-Mo 8 O 26 )] (8) [bix =1,4-bis(imidazole-1-ylmethyl)benzene, bpp=1,3-bis(4-pyridyl)propane]. Their structures were determined by single-crystal X-ray diffraction. In compounds 1 and 2, four copper cations are linked by octamolybdate isomers to generate a 2D layer with (4,4) sheet, which is pillared by bix ligands to form a 3D (4,4)-connected framework with (6 4 3 8 2 )(8 4 3 12 2 ) and (6 2 3 8 1 ) 2 (6 2 3 8 2 3 10 2 ) topologies, respectively. With the peneation of the copper-organic polymeric chains, a 3D polythreaded framework was formed. Compound 3 has a 3D supramolecular network based upon (β-Mo 8 O 26 ) 4anions and copper-organic units, with guest (β-Mo 8 O 26 ) 4anions included. In compound 4, a 3D supramolecular arrangement is constructed by the hydrogen-bond interactions between (β-Mo 8 O 26 ) 4polyanions from different 2D structures and bix ligands. Compound 5 exhibits a unique bisupported structure built from Mo-N covalent bonds between (γ-Mo 8 O 26 ) 4anions and bix ligands. This compound represents a rare example of organicmolecule-functionalized POM clusters that can be synthesized under hydrothermal conditions. In compound 6, a 3D supramolecular net is generated by hydrogen bonding interactions among water molecules, oxygen atoms of octamolybdate and nitrogen atoms of bix ligands. In compound 7, the bpp ligands link Cu cations and (R-Mo 8 O 26 ) 4anions to generate a 1D ladder-like chain.[Cu(bpp)] 2 2þ fragments further connect with (R-Mo 8 O 26 ) 4anions from different chains to form a 2D (3,4)-connected layer with (4 2 8 1 )(6 1 8 4 10 1 ) topology. Compound 8 also has 3D supramolecular framework based on C-H 3 3 3 O hydrogen bonds between bpp and (β-Mo 8 O 26 ) 4polyoxoanions. It is proposed that the different basicity, steric hindrance, and reducing strength of the bases used are the key factors in generating different Mo8 isomers in the reaction process, and thus the different frameworks as seen in 1-8. A ligand synergetic effect is also taken into account to explain the presence of the same Mo8 isomers in 7 and 8, which were synthesized with different bases. IR, TG, and electrochemistry study were performed to further characterize these compounds.

International audienceThe palladium-catalysed direct arylation of methyl 2-furoate with aryl bromides was studied. The use of KOAc as the base, dimethylacetamide (DMAc) as the solvent and Pd(OAc)2 as the catalyst was found to give 5-arylfurans regioselectively and without decarboxylation. These methyl 5-aryl-2-furoates gave 2,5-diarylfurans by decarboxylative coupling by using Pd(OAc)2 as the catalyst. Methyl 2-furoate thus represents a convenient alternative substrate to furan for the synthesis of mono- or poly-arylated furans

Previously, adsorption feature of a dirhamnolipid biosurfactant on diverse microbial cells was studied and the effect of the adsorption on cell surface hydrophobicity was compared. In this paper, the adsorption behavior of a monorhamnolipid and a dirhamnolipid on cells of two Pseudomonas aeruginosa strains was investigated in order to further reveal the influence of biosurfactant structure and cell property on the adsorption and the relation between the adsorption and cell surface hydrophobicity. Experimental results showed that the adsorption capacity of all the cells to monorhamnolipid was much stronger than to dirhamnolipid, and the rhamnolipid-sourced P. aeruginosa cells, no matter grown on glucose or hexadecane, released extra dirhamnolipid when aqueous concentration of dirhamnolipid was too high. Length of surfactant alkyl chain as well as the type of carbon source used to cultivate the cell adsorbents had only minor influence on the adsorption. The adsorption was assumed to be driven by polar interaction between the rhamnolipid molecules and the cell surface chemical groups. The directional orientation of the rhamnolipid molecules with hydrophobic moiety extending to the environment may account for the rapid increase of cell surface hydrophobicity at low aqueous concentrations of the surfactant, while the stable or decreased cell hydrophobicity was probably the consequence of multiple surfactant layer formation or hemimicelle accumulation.

International audienceThe palladium-catalyzed direct arylation of furans or thiophenes that contained secondary carboxamides at the C2 position proceeded regioselectively at either the C3 or C5 positions, depending on the reaction conditions. The nature of the base was crucial for controlling the regioselectivity of the reaction. We had previously observed that, in the presence of potassium acetate, direct arylation at the C5 position was favored. Herein, we report that the use of cesium carbonate as the base and xylene as the solvent selectively afforded the C3-arylated furans or thiophenes. The reactivity of furan-2-carboxamides and thiophene-2-carboxamides were similar. The reaction tolerated a range of functional groups on the aryl bromide and also heteroaryl bromide substrates

Five unique Keggin-type polyoxometalate (POM)-based metal−organic frameworks (POMFs), namely= 1,4-bis((1H-1,2,4-triazol-1-yl)methyl)-benzene, have been synthesized under ionothermal conditions. According to single-crystal data, 1 exhibits a novel mechanically interlocked molecular architecture (MIMA) constructed by two-dimensional (2D) interpenetrating polyrotaxane layers with unique cyclophanes (tetra-cationic viologen macrocycle cyclobis-(paraquat-p-phenylene) (CBPQT 4+ system)), resulting in an H-bonded 3D supermolecule, and is the first synthesis of selfassembled cyclophane-PMOFs under ionothermal conditions. 2 shows a novel 2D three-fold interpenetrating polyrotaxane host and guest network. 1 and 2 are presented as the first MIMA polyrotaxane structures to have been synthesized under ionothermal conditions. Electrochemical impedance spectroscopy (EIS) reveals that 2, 4, and 5 show high proton conductivity owing to their unique structural properties. Solid-state diffuse reflection UV−vis-NIR measurements show the title compounds are potentially semiconductor materials. Photocatalytic investigations indicate that 1−5 possess high and stable photocatalytic H 2 evolution and rhodamine B (RhB) degradation under visible-light irradiation.