Eric Léonel

Synthesis of small metallic Mg-based nanoparticles confined in porous carbon materials for hydrogen sorption

MgH2, Mg-Ni-H and Mg-Fe-H nanoparticles inserted into ordered mesoporous carbon templates have been synthesized by decomposition of organometallic precursors under hydrogen atmosphere and mild temperature conditions. The hydrogen desorption properties of the MgH2 nanoparticles are studied by thermo-desorption spectroscopy. The particle size distribution of MgH2, as determined by TEM, is crucial for understanding the desorption properties. The desorption kinetics are significantly improved by downsizing the particle size below 10 nm. Isothermal absorption/desorption cycling of the MgH2 nanoparticles shows a stable capacity over 13 cycles. The absorption kinetics are unchanged though the desorption kinetics are slower on cycling.

An Electrochemical Nickel-Catalyzed Arylation of 3-Amino-6-Chloropyridazines

3-Amino-6-aryl- and 3-amino-6-heteroarylpyridazines have been obtained in generally good yield using a nickel-catalyzed electrochemical cross-coupling between 3-amino-6-chloropyridazines and aryl or heteroaryl halides at room temperature. Comparative experiments involving classical palladium-catalyzed reactions, such as Suzuki, Stille, or Negishi cross-couplings, reveal that the electrochemical method can constitute a reliable alternative tool for biaryl formation. A possible reaction mechanism is proposed on the basis of electrochemical analyses.

Cyclopropane formation by electroreductive coupling of activated olefins and gem-polyhalo compounds

Abstract Cyclopropyl derivatives have been prepared with satisfactory yields by electroreductive coupling of activated olefins and gem -polyhalo compounds. The reaction is efficient when the olefin is more easily reduced than the organic halide. Two types of intermediates can be involved to lead to the products. The radical anion of the olefin can react with the halo compound by electron-tranfer followed by radical coupling, or be reduced into the dianion which reacts by nucleophilic displacement.

Synthesis and cytotoxic evaluation of novel paraconic acid analogs

A novel class of 2,3-tri- and tetrasubstituted γ-butyrolactones analogous to paraconic acids has been synthesized in one step using a straightforward three-component reaction among aryl bromides, dimethyl itaconate and carbonyl compounds. The in vitro cytotoxic activity of representative compounds has been evaluated against a panel of human cancer cell lines (KB, HCT116, MCF7, HL60). While most molecules exhibit a low to moderate background activity on both KB and HL60 cancer cell lines, one compound shows increased antiproliferative activities against both cell lines with IC(50) values in the 10(-7)-10(-6)mol/L range. An extended evaluation indicated that this compound also inhibits PC3, SK-OV3, MCF7R and HL60R cell growth in the same fashion.

Copper-catalyzed electrosynthesis of 1-acyl-2,2-diphenylcyclopropanes and their behaviour in acidic medium

The formation of 1-acyl-2,2-diphenylcyclopropanes is performed under mild electrochemical conditions. These cyclopropane derivatives, through acid-catalyzed ring-opening, lead to γ,γ-diphenyl-β,γ-unsaturated carbonyl compounds which evolve into either substituted naphthalenes, or β-benzhydryl-α,β-cycloalkenones depending on the acyclic or cyclic nature of the intermediate allyl ketone.

Cyclopropane formation by nickel-catalysed electroreductive coupling of activated olefins and unactivated gem-dibromo compounds

Abstract Cyclopropyl derivatives have been prepared with good yields by transition-metal catalysed electroreductive coupling of activated olefins and unactivated gem-dibromo compounds. This electrolysis is characterized by the use of a Fe/Ni catalyst system, acetonitrile as the solvent and a catalytic amount of triphenylphosphine as ligand. This procedure is a good alternative to the classical preparations of cyclopropyl derivatives from activated olefins (Simmons–Smith reaction, 1,3-dipolar addition of diazomethane, 1,4-addition of phosphorus and sulfur ylides).

Electrochemical Synthesis and Characterisation of Alternating Tripyridyl-Dipyrrole Molecular Strands with Multiple Nitrogen-Based Donor-Acceptor Binding Sites

Synthesis of alternating pyridine-pyrrole molecular strands composed of two electron-rich pyrrole units (donors) sandwiched between three pyridinic cores (acceptors) is described. The envisioned strategy was a smooth electrosynthesis process involving ring contraction of corresponding tripyridyl-dipyridazine precursors. 2,6-Bis[6-(pyridazin-3-yl)]pyridine ligands 2a-c bearing pyridine residues at the terminal positions were prepared in suitable quantities by a Negishi metal cross-coupling procedure. The yields of heterocyclic coupling between 2-pyridyl zinc bromide reagents 12a-c and 2,6-bis(6-trifluoromethanesulfonylpyridazin-3-yl)pyridine increased from 68 to 95% following introduction of electron-donating methyl groups on the metallated halogenopyridine units. Favorable conditions for preparative electrochemical reduction of tripyridyl-dipyridazines 2b,c were established in THF/acetate buffer (pH 4.6)/acetonitrile to give the targeted 2,6-bis[5-(pyridin-2-yl)pyrrol-2-yl]pyridines 1b and 1c in good yields. The absorption behavior of the donor-acceptor tripyridyl-dipyrrole ligands was evaluated and compared to theoretical calculations. Highly fluorescent properties of these chromophores were found (ν(em)≈2 × 10(4) cm(-1) in MeOH and CH(2)Cl(2)), and both pyrrolic ligands exhibit a remarkable quantum yield in CH(2)Cl(2) (φ(f)=0.10). Structural studies in the solid state established the preferred cis conformation of the dipyrrolic ligands, which adopting a planar arrangement with an embedded molecule of water having a complexation energy exceeding 10 kcal mol(-1). The ability of the tripyridyl-dipyrrole to complex two copper(II) ions in a pentacoordinate square was investigated.

An Electrochemical Synthesis of Functionalized Arylpyrimidines from 4-Amino-6-Chloropyrimidines and Aryl Halides

A range of novel 4-amino-6-arylpyrimidines has been prepared under mild conditions by an electrochemical reductive cross-coupling between 4-amino-6-chloro-pyrimidines and functionalized aryl halides. The process, which employs a sacrificial iron anode in conjunction with a nickel(II) catalyst, allows the formation of coupling products in moderate to high yields.

Efficient Route to Medium‐Ring Benzo‐ and Azabenzo‐lactones

Abstract The synthesis of precursors of medium‐ring benzo‐ and azabenzo‐lactones is performed efficiently from simple ortho‐halo aryl and heteroaryl aldehydes.

Synthesis of 6-, 7-, and 8-membered lactones via the nickel-catalysed electrochemical arylation of electron-deficient olefins

Abstract A nickel-catalysed electroreductive process of arylation of α,β-unsaturated carboxylic esters has been applied to the synthesis of medium-sized lactones. Of the two possible approaches investigated in this study, the most efficient one involves first the electrochemical condensation, followed by the lactonisation.