Desenvolvimento de sistemas catalíticos para transformação de aldeídos α,β-insaturados

Abstract

In this dissertation were developed catalytic processes employing different types of catalysts (heterogeneous and homogeneous) in the transformation of several α,β-unsaturated aldehydes. Heterogeneous catalysts of ruthenium and ruthenium/tin were prepared by the sol- gel methodology for application in the selective hydrogenation of terpenic aldehydes aiming the formation of the respective allylic alcohols. The prepared materials were characterized by diverse physicochemical, spectroscopic and microscopy techniques for a better understanding of the catalytic materials structure. Bimetallic ruthenium/tin catalyst presented an elevated selectivity for the unsaturated alcohol due to the properties of catalytic sites. In the next chapter, it was demonstrated a novel tandem route starting from α,β-unsaturated aldehydes to synthesize the respective allylic acetates, products of great industrial relevance. Here, it was employed the same ruthenium catalyst prepared by the sol-gel method used for the selective hydrogenation. The ruthenium catalyst was able to promote the selective hydrogenation of C=O bond while silanol acidic groups assisted the acetalization step of allylic alcohol. Benzaldehyde acetate was obtained in 86% yield, while the esther from cinnamaldehyde could be obtained in 40% yield. In the further chapter, it was demonstrated the hydroamination of allylic alcohols with several amines catalyzed by manganese organometallic complexes with pincer-type ligands for the synthesis of g-amino alcohols in up to 96% yield using up to 2 mol% of catalyst. This transformation was enabled by the characteristic feature of hydrogen transfer known for this type of ligands. The use of this methodology avoids the use of toxic reactants like acrolein for the production of g-amino alcohols.