Síntese de derivados de tioéteres via reação de acoplamento cruzado C-S empregando um catalisador heterogêneo de cério (III)

Abstract

Cross-coupling reactions are considered a powerful strategy to form carbon-carbon and carbonheteroatom bonds. Despite the elegance of the cross-coupling reaction due to the wide application of different nucleophiles such as chalcogenides there are some drawbacks in its implementation. On the other hand, the biological and medicinal properties of organocalcogen compounds have been studied. One of the groups of organocalcogenic that stand out are the thioethers, which can be synthesized by C-S cross-coupling reaction. The first published report about C-S cross-coupling was described by Migita and co-authors using a palladium (0) catalyst for thioethers synthesis. In contrast, Nageswar and co-authors reported the first C-S cross coupling using lanthanides for the formation of thioethers. Motivated by the work of Nageswar and co-authors regarding C-S cross coupling using lanthanides, in this work we carried out the cross-coupling reaction for the formation of various thioethers derivatives using the heterogeneous catalyst [Ce(L-Pro)2]2Ox, a catalyst developed in our laboratory. In this work, thioethers were synthesized through C-S cross-coupling reaction using thiols and aryl iodides, in the presence of the cerium (III) catalyst. In the development of thioethers synthesis, the preferred reaction parameters were determined for obtaining the (4-nitrophenyl)(phenyl)sulfane and after this, a set of nineteen compounds derived from the standard thioether was formed (yields from 15% to >99%), all of which were purified via column chromatography (appropriate quantities of hexane and ethyl acetate) and characterized via FT-IR, 1H and 13C NMR. Subsequently, the possibility of reusing the cerium catalyst in five reaction cycles was verified and a scale up synthesis of a precursor of the Dapsone drug was also carried out, excellent results were obtained for both studies.