4 research outputs found

    Palladium-Catalyzed Oxidative Direct C3- and C7-Alkenylations of Indazoles: Application to the Synthesis of Gamendazole

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    The first palladium-catalyzed oxidative alkenylation of (1<i>H</i>)- and (2<i>H</i>)-indazole derivatives with various olefins is described. The use of Pd­(OAc)<sub>2</sub> as the catalyst and Ag<sub>2</sub>CO<sub>3</sub> as the oxidant promoted the selective C3-monoalkenylation of (1<i>H</i>)-indazoles and (2<i>H</i>)-indazoles, affording the desired products in good yields. An original oxidative C7-alkenylation of 3-substituted (1<i>H</i>)-indazoles was also developed. The oxidative alkenylation of (1<i>H</i>)-indazole was successfully applied to the total synthesis of the drug candidate gamendazole in a step- and atom-economical fashion

    Palladium-Catalyzed Direct C7-Arylation of Substituted Indazoles

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    A novel direct C7-arylation of indazoles with iodoaryls is described using Pd­(OAc)<sub>2</sub> as catalyst, 1,10-phenanthroline as ligand, and K<sub>2</sub>CO<sub>3</sub> as base in refluxing DMA. Direct C7-arylation of 3-substituted 1<i>H</i>-indazole containing an EWG on the arene ring gave the expected products in good isolated yields. In addition, a one-pot Suzuki–Miyaura/arylation procedure leading to C3,C7-diarylated indazoles has been developed

    Orthogonal Synthesis of Covalent Polydendrimer Frameworks by Fusing Classical and Onion-Peel Phosphorus-Based Dendritic Units

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    We report novel and new giant three-dimensional polymers having dendrimers as repeating units. The approach is illustrated here for macromolecular synthesis by polymeric condensation of well-defined single phosphorus dendrimers units. Specifically, classical and onion-peel phosphorus dendrimers, constructed by a divergent method from a cyclotriphosphazene core, were fused within the same tectonic nanostructure by several polymeric condensation approaches including hydrazine-to-aldehyde Schiff-base formation and amine-to-carboxylic acid peptide-like coupling. These reticular, easy to run metal-free routes afford a new library of hyperbranched macromolecular materials, featuring various phosphorus layers (both alternated and dissymmetrical), well-defined textured nanospheres, and controllable nanometric ordered substructures. The scope of the concept is successfully expanded to the integration of electro-redox viologen units resulting in the synthesis of new photoactive macromolecular materials

    Biological Activity of Mesoporous Dendrimer-Coated Titanium Dioxide: Insight on the Role of the Surface–Interface Composition and the Framework Crystallinity

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    Hitherto, the field of nanomedicine has been overwhelmingly dominated by the use of mesoporous organosilicas compared to their metal oxide congeners. Despite their remarkable reactivity, titanium oxide-based materials have been seldom evaluated and little knowledge has been gained with respect to their “structure–biological activity” relationship. Herein, a fruitful association of phosphorus dendrimers (both “ammonium-terminated” and “phosphonate-terminated”) and titanium dioxide has been performed by means of the sol–gel process, resulting in mesoporous dendrimer-coated nanosized crystalline titanium dioxide. A similar organo-coating has been reproduced using single branch-mimicking dendrimers that allow isolation of an amorphous titanium dioxide. The impact of these materials on red blood cells was evaluated by studying cell hemolysis. Next, their cytotoxicity toward B14 Chinese fibroblasts and their antimicrobial activity were also investigated. Based on their variants (cationic versus anionic terminal groups and amorphous versus crystalline titanium dioxide phase), better understanding of the role of the surface–interface composition and the nature of the framework has been gained. No noticeable discrimination was observed for amorphous and crystalline material. In contrast, hemolysis and cytotoxicity were found to be sensitive to the nature of the interface composition, with the ammonium-terminated dendrimer-coated titanium dioxide being the most hemolytic and cytotoxic material. This surface-functionalization opens the door for creating a new synergistic machineries mechanism at the cellular level and seems promising for tailoring the biological activity of nanosized organic–inorganic hybrid materials
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