Mesoporous niobiosilicate NbMCF modified with alkali metals in the synthesis of chromene derivatives
| Autor: | Izabela Sobczak, Maria Ziolek, Agata Smuszkiewicz, Elena Pérez-Mayoral, Elena Soriano, Jesús López-Sanz, Rosa M. Martín-Aranda |
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| Rok vydání: | 2016 |
| Předmět: |
Chemistry
Inorganic chemistry Diastereomer 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Heterogeneous catalysis Alkali metal 01 natural sciences Catalysis 0104 chemical sciences Metal Nucleophile visual_art visual_art.visual_art_medium Reactivity (chemistry) 0210 nano-technology Mesoporous material |
| Zdroj: | Catalysis Today. 277:133-142 |
| ISSN: | 0920-5861 |
| Popis: | We report the synthesis, characterization and activity of new series of catalysts based on Niobium Mesoporous Cellular Foams (NbMCF), modified with alkaline metal elements. These materials exhibit very different acid-base properties attributed to the Nb source for the preparation of the catalysts and the presence and loading of different alkaline metals. The Me/NbMCF materials (where Me are alkaline metals) were tested in the reaction of 2-hydroxybenzaldehyde and ethyl cyanoacetate, under solvent-free conditions, at room temperature, leading to mixtures of the corresponding chromenes 4 and 5, as mixtures of diastereomers erythro/threo, in a 2:1 ratio, respectively, with good to excellent yields. Our experimental results indicate that the metal loading on the catalysts and the acid-base character, and the texture parameters are probably determining factors in the reactivity and the observed diastereoselectivity. The computational study suggests that the presence of alkaline oxides on Me/NbMCF catalyst, exhibiting strong basicity, activates the formation of the nucleophile species, the corresponding enolate, and initiates the reaction. However, the cation size has a deep impact on the stability of the reactant complex so that the effective aldolization could be obstructed by the presence of the bulkier centers. |
| Databáze: | OpenAIRE |
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