Tetrazo[1,2-b]indazoles: Straightforward Access to Nitrogen-Rich Polyaromatics from s-Tetrazines

The straightforward access to a new class of aza-polyaromatics is reported. Starting from readily available fluorinated s-tetrazine, a cyclization process with azide leads to the formation of an unprecedented tetrazo[1,2-b]indazole or a bis-tetrazo[1,2-b]indazole (cis and trans conformers). Based on the new nitrogen core, further N-directed palladium-catalyzed ortho-C−H bond functionalization allows the introduction of halides or acetates. The physicochemical properties of these compounds were studied by a joint experimental/theoretical approach. The tetrazo[1,2-b]indazoles display solid-state π-stacking, low reduction potential, absorption in the visible range up to the near-infrared, and intense fluorescence, depending on the molecular structure.     

Preparation of functionalized aryl- and heteroarylpyridazines by nickel-catalyzed electrochemical cross-coupling reactions

A general efficient electrochemical method for the preparation of aryl- and heteroarylpyridazines in a nickel-catalyzed cross-coupling reaction of 3-chloro-6-methoxypyridazine and 3-chloro-6-methylpyridazine with a range of functionalized aryl or heteroaryl halides is reported.     

Stability estimates for some parameters of a reaction-diffusion equation coupled with an ODE

In this work, we are interested by the monodomain equation which describes the evolution of the cardiac electrical potential and which corresponds to a coupled system involving a reaction–diffusion equation and an ordinary differential equation. We show Lipschitz stability inequalities for the identification of some parameters of the model from measurements on the cardiac potential and the ionic variable.     

Dichotomic lattices and local discretization for Galois lattices

The present paper deals with supervised classification methods based on Galois lattices and decision trees. Such ordered structures require attributes discretization and it is known that, for decision trees, local discretization improves the classification performance compared with global discretization. While most literature on discretization for Galois lattices relies on global discretization, the presented work introduces a new local discretization algorithm for Galois lattices which hinges on a property of some specific lattices that we introduce as dichotomic lattices. Their properties, co-atomicity and \(\vee \)-complementarity are proved along with their links with decision trees. Finally, some quantitative and qualitative evaluations of the local discretization are proposed.     

Pyridyl‐Functionalised 3H‐1,2,3,4‐Triazaphospholes: Synthesis,Coordination Chemistry and Photophysical Properties of Low‐Coordinate Phosphorus Compounds

Novel conjugated, pyridyl‐functionalised triazaphospholes with either tBu or SiMe₃ substituents at the 5‐position of the N₃PC heterocycle have been prepared by a [3+2] cycloaddition reaction and compared with structurally related, triazole‐based systems. Photoexcitation of the 2‐pyridyl‐substituted triazaphosphole gives rise to a significant fluorescence emission with a quantum yield of up to 12 %. In contrast, the all‐nitrogen triazole analogue shows no emission at all. DFT calculations indicate that the 2‐pyridyl substituted systems have a more rigid and planar structure than their 3‐ and 4‐pyridyl isomers. Time‐dependent (TD) DFT calculations show that only the 2‐pyridyl‐substituted triazaphosphole exhibits similar planar geometry, with matching conformational arrangements in the lowest energy excited state and the ground state; this helps to explain the enhanced emission intensity. The chelating P,N‐hybrid ligand forms a Re^I complex of the type [(N^N)Re(CO)₃Br] through the coordination of nitrogen atom N² to the metal centre rather than through the phosphorus donor. Both structural and spectroscopic data indicate substantial π‐accepting character of the triazaphosphole, which is again in contrast to that of the all‐nitrogen‐containing triazoles. The synthesis and photophysical properties of a new class of phosphorus‐containing extended π systems are described.     

A New Way to Silicone‐Based Peptide Polymers

We describe a new class of silicone‐containing peptide polymers obtained by a straightforward polymerization in water using tailored chlorodimethylsilyl peptide blocks as monomeric units. This general strategy is applicable to any type of peptide sequences, yielding linear or branched polymer chains composed of well‐defined peptide sequences.     

Asymmetric synthesis of cyclohexene nucleoside analogues

The asymmetric synthesis of novel cyclohexene nucleoside analogues 12 and 15 is described. An enantiospecific Diels-Alder reaction between (E,E)-diene 2 and (+)-5-(d-mentyloxy)-2(5H)-furanone 3 provided the cycloadduct isomer 4. Three additional steps yielded amine 8 allowing the constructions of the thymine and adenine moieties to afford intermediates 11 and 14, respectively. Amination or cyclization and removal of the protecting groups occurred in one step in the presence of ammonia, giving the target six-membered ring nucleosides.     

Synthetic applications of the nickel-catalyzed cyclization of alkynes combined with addition reactions in a domino process

Carbonickelations of alkynes and functionalization of the resulting vinylnickel moiety have been performed efficiently in a nickel-catalyzed domino cyclization-condensation process. This reaction, which does not require the preparation of any other organometallic reagent, proceeds only by exo-dig cyclization. This convenient and mild method constitutes a one-pot synthesis of substituted dihydrobenzofurans, chromans, isochromans, indoles, or indanes. Theses valuable products are generally obtained in good yields and high stereoselectivity. They are shown to be useful synthons for rapid access to functionalized polycyclic skeletons.     

Stabilization of miniemulsion droplets by cerium oxide nanoparticles: a step toward the elaboration of armored composite latexes

Stable methyl methacrylate (MMA) miniemulsions were successfully prepared using for the first time cerium oxide (CeO(2)) nanoparticles as solid stabilizers in the absence of any molecular surfactant. The interaction between MMA droplets and CeO(2) nanoparticles was induced by the use of methacrylic acid (MAA) as a comonomer. Both MAA and CeO(2) contents played a key role on the diameter and the stability of the droplets formed during the emulsification step. Cryo-transmission electron microscopy (TEM) images of the suspensions formed with 35 wt % of CeO(2) showed the presence of polydisperse 50-150 nm spherical droplets. More surprisingly, some nonspherical (likely discoidal) objects that could be the result of the sonication step were also observed. The subsequent polymerization of these Pickering miniemulsion droplets led to the formation of composite PMMA latex particles armored with CeO(2). In all cases, the conversion was limited to ca. 85%, concomitant with a loss of stability of the latex for CeO(2) contents lower than 35 wt %. This stability issues were likely related to the screening of the cationic charges present on CeO(2) nanoparticles upon polymerization. TEM images showed mostly spherical particles with a diameter ranging from 100 to 400 nm and homogeneously covered with CeO(2). Besides, for particles typically larger than 200 nm, a buckled morphology was observed supporting the presence of residual monomer at the end of the polymerization and consistent with the limited conversion. The versatility of these systems was further demonstrated using 35 wt % of CeO(2) and replacing MMA by n-butyl acrylate (BA) either alone or in combination with MMA. Stable monomer emulsions were always obtained, with the droplet size increasing with the hydrophobicity of the oil phase, pointing out the key influence of the wettability of the solid stabilizer. The polymerization of Pickering miniemulsion stabilized by CeO(2) nanoparticles proved to be an efficient strategy to form armored composite latex particles which may find applications in coating technology.     

Synthesis of Porous PEG Microgels Using CaCO3 Microspheres as Hard Templates

Porous poly(ethylene glycol) (PEG) microgels of both 17.6 and 8.3 μm in diameter are synthesized via hard templating with calcium carbonate (CaCO₃) microparticles. The synthesis is performed in three steps: loading of PEG macromonomers into CaCO₃ microparticles, crosslinking via photopolymerization, and removal of the CaCO₃ template under acidic conditions. The resulting porous PEG microgels are inverse replicates of their templates as indicated by light microscopy, cryo‐scanning electron microscopy (cryo‐SEM), and permeability studies. Thus this process allows for the straightforward and highly reproducible synthesis of porous hydrogel particles of two different diameters and porosities that show great potential as carriers for drugs or nanomaterials.