An organometallic route for the preparation of ring-substituted 2-aryl-propanoic and -butanoic acids

This communication presents a simple and efficient way to synthesize 2-arylalkanoic acids via chromium carbonyl complexation.     

Synthetic approaches to trialkyl(ferrocenylmethyl)ammonium salts as cationic templates for the preparation of ferromagnets on the basis of bimetal oxalates

Trialkyl(ferrocenylmethyl)ammonium salts and their 2-substituted analogs designed for the preparation of molecular ferromagnetics based on bimetallic oxalates were synthesized using classical alkylation of dialkylaminomethylferrocenes by alkyl halides and nucleophilic substitution reaction of 2-substituted dimethylaminomethylferrocene methiodides with trialkylamines. In the case of salts with electron-donating substituents in position 2, only the latter of the two proposed routes is applicable because N-alkylation with alkyl halides is accompanied by competing ferrocenylmethylation of the starting amine. On the contrary, the salts with electron-withdrawing 2-substituents should be prepared preferably by the reaction of amines with alkyl halides, while nucleophilic trialkylamination of methiodides is complicated by deprotonation induced by bases.     

Design of multifunctionalized γ-Fe2O3@SiO2 core–shell nanoparticles for enzymes immobilization

This article deals with the first covalent grafting of an enzyme on twice functionalized γ-Fe₂O₃@SiO₂ core–shell magnetic nanoparticles. First, amino-PEG functionalized nanoparticles were synthesized in order to comply with non-toxic platforms that would be stable in high concentration and would exhibit chemical groups to allow further coupling with biomolecules. This approach produces a colloidal suspension of covalently grafted enzymes that remains stable for months and mimics the enzyme–substrate interactions in solution. Secondly, nanoparticles synthesis and enzyme coupling process were reported and the catalytic properties of bound enzymes were measured and compared with that of the free one. These new materials appear to be useful tools for enzymatic catalysis research and may be extended to other biomolecules. Furthermore, magnetic properties of these materials open the way to separation, purification, and transport under magnetic field.     

Stereochemical control in reactions of chiral ketone with 2-lithiated substituted ferrocene derivatives

The formation of a new chiral center in the reactions of ketone 4-MeOC₆H₄CH(Et)C(O)Et with planar-chiral 2-lithio-1-methyl- and 1-chloro-2-lithioferrocenes proceeded stereoselectively to give two diastereomers in a ratio of 3 : 2 or a single diastereomer, respectively, out of four possible diastereomeric 4-aryl-3-ferrocenylhexan-3-ols. The replacement of the hydroxy group in the resulting compounds by hydrogen under the conditions of ionic hydrogenation was studied. The configurations of the reaction products were established by X-ray diffraction analysis and ¹H NMR spectroscopy.     

Use of a chromium tricarbonyl complex in a diels–alder reaction: Improved preparation of angularly trifluoromethyl-substituted tetrahydrophenanthrone

The tricarbonyl complex prepared from 1-trifluoromethyldihydronaphthalene and Cr(CO)₃(NH₃)₃ undergoes Diels–Alder cycloaddition under high-pressure conditions (15 kbar) to give after decomplexation by natural light and deprotection, the tetrahydrophenanthrone product in 65% yield. This new methodology allows the activation of unreactive styrenes in Diels–Alder cycloaddition.     

An eco-friendly route to magnetic silica microspheres and nanospheres

A green and inexpensive alternative to existing methods for the preparation of magnetic iron oxide/silica nanocomposite particles has been investigated. The use of water-in oil emulsions based on vegetable oils instead of usual solvents led to microsized or nanosized magnetic silica spheres exhibiting similar characteristics to those of classical procedures. Furthermore this approach is very general since a large class of porous magnetic colloids differing in size or iron oxide fraction has been obtained. This work emphasizes the importance of the level of the shearing during the emulsification step with regard to the size and monodispersity of the prepared beads. All the materials prepared were fully characterized (SEM and TEM microscopies, SQUID magnetometry, N(2) sorption volumetry, etc.). In addition, samples functionalized by thiol groups have been synthesized and successfully tested for the removal of heavy metals in water-treatment.