Publicação
Hybrid core-shell nanogels as catalytic nanoreactors
| Resumo: | Tailor-made nanogels prepared via reversible addition-fragmentation chain-transfer (RAFT) polymerization were successfully applied as support material for palladium(0) nanoparticles. Besides stabilizing the metal nanoparticles for at least one year, this hybrid nanogel catalyst was successfully applied for the Mizoroki-Heck cross-coupling reaction. This C-C coupling reached good yields in 2 hours at 120°C in dimethylacetamide with low catalyst loadings (0,1 mol% Pd). It showed a broad catalytic scope ranging from bromo-arenes (with electron withdrawing groups) to iodo-arenes (with either electro-withdrawing, electron-donating or without substituents) and different olefins. The catalyst did not present any problem upon the catalysis of substrates with functional groups in different position relative to the halogen, with the exception of functional groups with carbonyl in ortho position. These substrates presented a notable decrease in the coupling yield. Furthermore, the reactivity of methacrylates was subject of a deep investigation showing the formation of an uncommon bis-arylated product. Despite good results in simple couplings, the hybrid nanogel catalyst system was proven inefficient when applied to more complex systems such as intramolecular tandem Mizoroki-Heck reaction, and the synthesis of specific molecules scaffolds such as indenes and coumarins. Finally, a Collman´s test with macromolecular substrates demonstrated signs of leaching of the metal during the catalysis by the hybrid nanogel. |
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| Autores principais: | Nunes, Danilo Rosa |
| Assunto: | Catalysis Mizoroki-Heck reaction Nanoparticles Hybrid nanogel Mestrado Integrado - 2016 |
| Ano: | 2016 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso restrito |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Tailor-made nanogels prepared via reversible addition-fragmentation chain-transfer (RAFT) polymerization were successfully applied as support material for palladium(0) nanoparticles. Besides stabilizing the metal nanoparticles for at least one year, this hybrid nanogel catalyst was successfully applied for the Mizoroki-Heck cross-coupling reaction. This C-C coupling reached good yields in 2 hours at 120°C in dimethylacetamide with low catalyst loadings (0,1 mol% Pd). It showed a broad catalytic scope ranging from bromo-arenes (with electron withdrawing groups) to iodo-arenes (with either electro-withdrawing, electron-donating or without substituents) and different olefins. The catalyst did not present any problem upon the catalysis of substrates with functional groups in different position relative to the halogen, with the exception of functional groups with carbonyl in ortho position. These substrates presented a notable decrease in the coupling yield. Furthermore, the reactivity of methacrylates was subject of a deep investigation showing the formation of an uncommon bis-arylated product. Despite good results in simple couplings, the hybrid nanogel catalyst system was proven inefficient when applied to more complex systems such as intramolecular tandem Mizoroki-Heck reaction, and the synthesis of specific molecules scaffolds such as indenes and coumarins. Finally, a Collman´s test with macromolecular substrates demonstrated signs of leaching of the metal during the catalysis by the hybrid nanogel. |
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