Despite their clinical importance, saving numerous human lifes, over- and mis-uses of antibiotics have created a strong selective pressure on bacteria, which induces the emergence of (multi)resistant strains. Antibioresistance is becoming so pregnant that since 2017, WHO lists bacteria threatening most human health (AWaRe, ESKAPE lists), and those for which new antibiotics are urgently needed. Since the century turn, this context is leading to a burst in the chemical synthesis of new antibiotics, mostly derived from natural antibiotics. Among them, aminoglycosides, and especially the neomycin family, exhibit broad spectrum of activity and remain clinically useful drugs. Therefore, numerous endeavours have been undertaken to modify aminoglycosides with the aim of overcoming bacterial resistances.

Herein, the effect of various treatments subjected to FAU zeolites to introduce mesoporosity has been examined on their efficiency as catalyst in the cyclisation of O-aryl 3-arylpropynoic acid ester to its corresponding coumarin. The addition of bio-sourced lignin residues in the alkaline desilication treatment induced the generation of supplementary mesoporosity, thus offering an optimal micro- and mesopores combination with respect to targeted activity and selectivity. The so-called bio-sourced secondary template (BSST) concept in the design of zeolite-based catalysts could be assessed. The use of renewable wood feedstocks can therefore be a valuable strategy for the zeolite postmodification, thus for the design of porous zeolite catalysts.

AbstractSilver salts or complexes promote a variety of useful C—C bond-forming transformations in organic synthesis, usually under very mild conditions. In these reactions, silver can be engaged either as catalyst or cocatalyst, or as an organometallic reagent. Organosilver species act as mild nucleophiles toward alkyl halides or epoxides, but also toward carbonyl and imine derivatives and related heterocycles such as pyridines or quinolines. Silver can promote the homocoupling of a variety of organometallic reagents, of heterocycles, and of electron-deficient alkenes upon addition of the corresponding fluoride salts. Silver also promotes the cross coupling of alkyl or aryl halides, alkenes and alkynes, and even (het)arenes. Furthermore, silver salts often improve the efficiency of palladium-catalyzed cross-coupling reactions, or coupling reactions involving C—H activation or decarboxylation.

Silver salts or complexes promote a variety of useful C-C bond-forming transformations in organic synthesis, usually under very mild conditions. In these reactions, silver can be engaged either as catalyst or cocatalyst, or as an organometallic reagent. Organosilver species act as mild nucleophiles toward alkyl halides or epoxides, but also toward carbonyl and imine derivatives and related heterocycles such as pyridines or quinolines. Silver can promote the homocoupling of a variety of organometallic reagents, of heterocycles, and of electron-deficient alkenes upon addition of the corresponding fluoride salts. Silver also promotes the cross coupling of alkyl or aryl halides, alkenes and alkynes, and even (het)arenes. Furthermore, silver salts often improve the efficiency of palladium-catalyzed cross-coupling reactions, or coupling reactions involving C-H activation or decarboxylation.[GRAPHICS].

a) Laboratoire de Synthèse Réactivité Organiques et Catalyse (LASYROC), UMR 7177, Institut de Chimie, Université de Strasbourg, 1, rue Blaise Pascal, 67000 Strasbourg Cedex, France. E-mail: blouis@unistra.fr b) Université de Haute Alsace (UHA), CNRS, Equipe Matériaux à Porosité Contrôlée (MPC), Institut de Science des Matériaux de Mulhouse (IS2M) UMR 7361, ENSCMu, Mulhouse Cedex 68093, France. E-mail: jean.daou@uha.fr c) Institut de Chimie des Milieux et Matériaux de Poitiers, UMR 7285 CNRS, 4 Rue Michel Brunet, Bâtiment B27, 86073 Poitiers Cedex9 France.

Within the green chemistry context, heterogeneous catalysis is more and more applied to organic synthesis. The well known ‘click chemistry’ and especially its flagship, the copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC), is now catch up by such heterogenisation process and copper ions or metals have been grafted or deposited on or into various solids, such as (bio)polymers, charcoal, silica, zeolites, POM or MOF.

Continuous iodobenzene chlorination reaction: experimental set-up and conversion – acid site density dependence.

Correction to: Synthesis of Azabicycloalkanes by Gold(I)-Catalyzed Amination of YnonesSynfacts 2016; 12(09): 0901-0901DOI: 10.1055/s-0035-1562569

Scandium-exchanged USY zeolites were synthesized by vapor-phase exchange of parent HUSY with scandium trifluoromethanesulfonate (triflate) Sc(OSO2CF3)(3). Several FAU zeolites having scandium loadings ranging from 2 to 30 mol % were prepared and applied as catalysts to aza-Diels-Alder reaction in order to establish structure and catalytic properties relationships. Calcination at 623 K for 72 h led to preservation of the zeolite crystallinity along with the presence of different extra-framework aluminum species (EFAl) and scandium species, thus providing high Lewis acidity. Observation of the catalyst before, during, and after reaction, by multinuclear MAS NMR techniques and H/D isotope labeling, revealed the modification of aluminum and scandium environments within the zeolite framework. Recycling experiments stated for a truly heterogeneous catalytic path over these Sc USY zeolites. In contrast to the homogeneous version for the aza-Diels-Alder reaction, the present heterogeneous new version provided a green route for quantitative synthesis of tetrahydropyridines via bifunctional heterogeneous catalysis.

Mononuclear Cu(II) bipyridine (1) and phenantroline complexes (2) were synthesized and immobilized by different procedures on H3PW12O40 polyoxometalate (POM). Characterization by XRD and SEM-EDX were performed to assess the preservation of the Keggin structure and stoichiometry of the complex. The immobilized complexes were tested as heterogeneous catalysts for the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene) using hydrogen peroxide as oxidant in acetonitrile/water as solvent. [Cu(2,2'-bpy)Cl][H2PW12O40] and [Cu(1,10-phen)Cl][H2PW12O40] oxidized tetralin at room temperature, with 16% conversion with (2), to 1-tetralone and 2-tetralone with 83% selectivity. However, the selectivity for 1-tetralone was only 56%. Different preparation methods for the heterogenization of these complexes on the POM Keggin unit were compared and used to enhance the selectivity to 1-tetralone to 75%.

CuI-USY catalyzed the one-pot, two-step cascade reaction of halides (Cl, Br, I) with sodium azide and alkynes in degassed water under anoxic conditions to give the corresponding triazoles in up to 98% yield (22 examples). In the reaction of benzyl bromide and phenyl acetylene, the catalyst was recovered and reused four times without significant loss of its catalytic activity.

Cu-exchanged USY zeolite was synthesized by vapor-phase exchange of parent HUSY with CuCl. Reaction parameters were varied in order to investigate the relationship between the structure of Cu+-promoted FAU zeolites and their catalytic properties in C-C bond homocoupling reaction between two acetylenic molecules (Glaser reaction). A proper choice in the CuCl chemical vaporization duration and temperature led to an increase in extra-framework aluminum species formation and thus to higher Lewis acidity. Moreover, such treatment under nitrogen flow during two days at 623 K kept the material highly crystalline. A drastic influence of the zeolite topology and properties (channels or cages, pore diameter, acidity) was noticed in the conversion of phenylacetylene. Observation of the catalyst before, during, and after the reaction, by multinuclear magic-angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and H/D isotope labeling, revealed the necessity for the zeolite to still exhibit both Bronsted and Lewis acidity, after exchange with Cu+ cations. Indeed, the reversible change in copper cations oxidation state from + I to + II was demonstrated by XPS, thus confirming a heterogeneous catalytic process over zeolites to perform terminal alkyne homocoupling reaction. In contrast to its homogeneous Glaser version, this study describes therefore a green route for the quantitative synthesis of diynes via bifunctional heterogeneous catalysis.

A copper zeolite Cu(I)-USY was prepared by treatment of H-USY, which was generated from NH4-USY upon heating (550 ˚C), with CuCl at 350 ˚C for three days. The three-component coupling reaction of amines 1, aldehydes 2 and terminal alkynes 3 was carried out in the presence of 7 mol% Cu of Cu(I)-USY to give the corresponding propargylamines 4 in 0-95% yield (18 examples). The catalyst was recycled four times without significant loss of catalytic activity.

A highly regioselective heterogeneously catalyzed [3+2] cycloaddition of primary alkynes with azides to afford triazoles in good to excellent yields is reported. Five different synthesized Cu(I)-modified zeolites have been investigated. Only terminal alkynes and aryl and benzyl azides have been tested in this reaction.

1-Trimethylsilyl-1-alkynes are selectively converted to the corresponding silver acetylides. Silver nitrate or triflate are used under neutral conditions, allowing other functional groups to remain unaffected.

Mono- or disilylated alpha,omega-diynes and disilylated triynes can be regioselectively homologated at each acetylenic end, silylated or not, by two and three, respectively, successive Pd/ Ag-catalyzed coupling reactions. Each coupling being selective either for terminal alkyne, trimethylsilylalkyne or for trialkylsilylalkyne, the combination of these coupling methods offers a unique and rapid access to polyunsaturated compounds. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).

In superacids HSO3F and CF3SO3H, it has been found that 3-arylindenones are very stable and exist as a doubly protonated species. NMR showed protonation both at the oxygen of the carbonyl group and at the C2 carbon of the indenone system. 3-Arylindenones proved however very sensitive to heat and light. Their [2+2] photodimerization under daylight has been studied.

According to the 1H and 13C NMR data, 3-arylpropynoic acids and their esters XC6H n -C≡C-CO2R (R = H, Me, Et) having electron-withdrawing substituents in the benzene ring (X = NO2, CN, COMe, CO2Me) exist in HSO3F at −80 to 0°C as XC6H n -C≡C-C+(OH)OR ions. Derivatives with other substituents (X = H, F, Me, MeO) in HSO3F or CF3SO3H above −40°C undergo protonation at the acetylenic carbon atom neighboring to the acid group to give unstable vinyl-type XC6H n -C+=CH-CO2R cations which are then transformed into mixtures of stereoisomeric (Z and E) fluorosulfonates or triflluoromethanesulfonates XC6H n -CY=CH-CO2R (Y = OSO2F, OSO2CF3), the E isomer prevailing.