Desenvolvimento e avaliação de sistemas catalíticos heterogêneos para reações de acoplamento carbono-carbono de Suzuki-Miyaura
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2019-02-21
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Universidade Federal de Goiás
Resumo
Suzuki-Miyaura cross-coupling reactions are one of the most efficient and powerful tools
for the formation of new carbon-carbon bonds, which have been widely applied in modern
organic synthesis and industrial processes. Generally, these reactions are carried out by
homogeneous catalysis, employing expensive palladium complexes such as PdCl2
associated with harmful phosphine ligands. However, these synthetic route presents
several drawbacks such as high associated toxicity, catalyst recovery difficulties and waste
disposal problems. In this context, several heterogeneous catalysts were proposed to
overcome the great challenge of separation and recovery of homogenous catalysts. Also,
a low-cost catalyst was presented as an alternative for the usage of palladium as the main
Suzuki-Miyaura cross-coupling catalyst. Palladium, Nickel, Copper and Cobalt catalysts
supported on niobium pentoxide (Nb2O5) were synthesized via wet impregnation method
and tested for the Suzuki-Miyaura coupling reaction between phenylboronic acid and 4-
bromoanisole. The catalysts were well characterized by scanning electron microscopy, N2
physisorption, X-ray diffraction, X-ray fluorescence, Thermogravimetry/Differential Thermal
Analysis. Both Copper and Cobalt catalyst did not show any activity towards Suzuki-
Miyaura cross-coupling reaction. Palladium catalyst resulted in high isolated yields (up to
91%) under optimized conditions. Satisfactory yields (up to 48%) were achieved employing
the Nickel catalyst. Recycling tests were performed and significant loss in activity was
observed after the first catalytic cycle, which can be attributed to catalyst loss during its
retrieval by filtration between cycles, leaching of the active phase, in particular for
Pd/Nb2O5 catalyst, or the poisoning by inorganic species (mostly potassium) on the spent
catalyst’s surface.
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SOUZA, G.B.M. Desenvolvimento e avaliação de sistemas catalíticos heterogêneos para reações de acoplamento carbono-carbono de Suzuki-Miyaura. 2019. 84 f. Dissertação (Mestrado em Engenharia Química) -Universidade Federal de Goiás, Goiânia, 2019.