New Vanadium Keggin Heteropolyacids Encapsulated in a Silica Framework : Recyclable Catalysts for the Synthesis of Highly Substituted Hexahydropyrimidines Under Suitable Conditions
Solid acid catalysts based on the direct incorporation of the vanadium Keggin heteropolyacid (PMo11V) structure during the synthesis of silica by the sol–gel technique, in acidic media using tetraethyl orthosilicate (PMo11VSiO21, PMo11VSiO22, PMo11VSiO23, and PMo11VSiO24), were prepared and characte...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2015 |
| País: | Argentina |
| Institución: | Universidad Nacional de La Plata |
| Repositorio: | SEDICI (UNLP) |
| Idioma: | inglés |
| OAI Identifier: | oai:sedici.unlp.edu.ar:10915/138838 |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/138838 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias Exactas Química Keggin heteropolyacids Silica sol–gel HPA included in silica matrix Trifluoromethylhexahydropyrimidines Multicomponent reaction |
| Sumario: | Solid acid catalysts based on the direct incorporation of the vanadium Keggin heteropolyacid (PMo11V) structure during the synthesis of silica by the sol–gel technique, in acidic media using tetraethyl orthosilicate (PMo11VSiO21, PMo11VSiO22, PMo11VSiO23, and PMo11VSiO24), were prepared and characterized by 31P-NMR, FT-IR, XRD, and textural properties (SBET). The acidic characteristics of the catalysts were determined by potentiometric titration with n-butylamine. A series of highly substituted hexahydropyrimidines were synthesized using these new materials, encapsulated in a silica framework, as catalyst in solvent-free conditions. This methodology requires short reaction time (1.5 h), a temperature of 80 °C in solvent free-conditions to obtain good to excellent yields of trifluoromethyl-hexahydropyrimidine derivatives. The Keggin catalyst embedded in the silica matrix is insoluble in polar media, which allows easy removal of the reaction products without affecting their catalytic activity. |
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