4 research outputs found
Palladium-Catalyzed Oxidative Direct C3- and C7-Alkenylations of Indazoles: Application to the Synthesis of Gamendazole
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 PdÂ(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
A novel direct C7-arylation
of indazoles with iodoaryls is described
using PdÂ(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 SuzukiâMiyaura/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
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 SurfaceâInterface Composition and the Framework Crystallinity
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 âstructureâbiological activityâ
relationship. Herein, a fruitful association of phosphorus dendrimers
(both âammonium-terminatedâ and âphosphonate-terminatedâ)
and titanium dioxide has been performed by means of the solâgel
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 surfaceâinterface
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
organicâinorganic hybrid materials