3 results
Search Results
2. Utilizing Nitroarenes and HCHO to Directly Construct Functional N-Heterocycles by Supported Cobalt/Amino Acid Relay Catalysis
- Author
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Jia‐Lu Sun, Chenggang Ci, Huanfeng Jiang, Pierre H. Dixneuf, Min Zhang, South China University of Technology [Guangzhou] (SCUT), Qiannan Normal College for Nationalities [Duyun] (QNCN), Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and The authors are grateful to the financial support of State Key Laboratoryof Pulp and Paper Engineering (2022C03), the National Natural Science Foundation of China (21971071, 22163007), the Natural Science Foundation of Guangdong Province (2023A1515012318 and2021A1515010155), and Guizhou Province Science Foundation ([2020]1Y050).
- Subjects
Nitroarenes and formaldehyde ,[CHIM]Chemical Sciences ,Reductive coupling ,General Medicine ,General Chemistry ,N-heterocyclic carbene ligands ,Imidazolines ,Catalysis ,Relay catalysis - Abstract
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.
- Published
- 2023
3. Silica-based fibers with axially aligned mesopores from chitin self-assembly and sol-gel chemistry
- Author
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Bruno Alonso, Nathalie Witczak, Cyril Vallicari, Bastien Lecourt-Capdeville, Mathis Guiraud, Laurent Vachoud, Krassimir L. Kostov, Stefan Spirk, Gregor Trimmel, Emmanuel Belamie, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), Université de Montpellier (UM), Démarche intégrée pour l'obtention d'aliments de qualité (UMR QualiSud), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Avignon Université (AU)-Université de La Réunion (UR)-Institut Agro Montpellier, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Montpellier (UM), Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Institute of Bioproducts and Paper Technology, Institute for Chemistry and Technology of Materials, NAWI, École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)
- Subjects
Fibers ,Sol-Gel ,Electrospinning ,Mechanics of Materials ,General Materials Science ,Self-assembly ,[CHIM.MATE]Chemical Sciences/Material chemistry ,General Chemistry ,Condensed Matter Physics ,Chitin Nanorods - Abstract
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.
- Published
- 2022
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