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International audience; Due to the generation of multiple intermediates during the nitroarene reduction, precise interception of single one to develop tandem reactions involving both C-C and C-N bond formations still remains a significant challenge. Herein, the relay catalysis of a supported bifunctional cobalt catalyst with L-proline has been successfully applied to establish a bran-new reductive annulation reaction of nitroarenes and formaldehyde, which enables direct and diverse construction of both symmetrical and unsymmetrical 1,3-diaryl imidazolines. It proceeds with operational simplicity, good substrate and functionality compatibility, and excellent step and atom-efficiency. Mechanistic studies reveal that the Co-catalyst exhibits a synergistic effect on the formation of key N-hydroxy imine, and the L-proline subsequently facilitates the key C-C bond formation. The current work opens a door to develop useful transformations with nitroarenes by reduction-interrupted strategy.

International audience; Polysaccharide nanorods (chitin, cellulose) can be used as colloidal templates to form silica-based mesoporous materials by combining self-assembly and sol-gel chemistry. Chitin nanorods are chosen here for their self-assembly properties, facile preparation from natural resources, and because of the complexing properties of the free amino groups at their surface in view of further functionalization. Electrospinning of ethanolic co-suspensions, containing the chitin nanorods as pore templates, siloxane oligomers as silica precursors and polyvinylpyrrolidone (PVP) as spinning polymer, allows for forming mats of hybrid organic-inorganic fibers with diameters in the 200-300 nm range. The relative proportions of each component can be adjusted to meet specific characteristics (e.g. micro-/mesoporosity ratio). After calcination, the fibers present an open porosity studied by TEM and N2 volumetry. Elongated mesopores (100-200 nm long, 2-4 nm wide) are created by individual chitin monocrystals forming the nanorods. They are highly oriented along the fibers' axes with orientational order parameters P2 > 0.95 for volume chitin contents chitin* ≥ 0.2. Additional microporosity is provided by the removal of the spinning polymer, PVP. Complementary viscosity measurements on the initial cosuspensions allow discussing the interactions between colloids and their possible impact on the materials' textures observed. The introduction of a monomeric Ti 4+ precursor in the co-suspensions leads to isolated and tetrahedral Ti units, distributed in the calcined porous silica fibers and possibly close to the pores surface. In addition, preliminary investigations on processing the fibers with a Zn xanthate as ZnS precursor leads to carbonized fibers with nanoparticles and a Zn/S molar ratio close to 1.