Transformações de compostos terpênicos via reações catalíticas: valorização de matéria-prima de origem natural

Abstract

In this work, new processes for the synthesis of fine chemicals products with high added value and commercial interest were developed using terpenes and their derivatives as substrates. The approach is the application of methods of catalysis by Solid-Acids andCatalysis by Nanostructured Metal to transform these substrates into fragrance products with properties that can be used as raw materials in cosmetic and pharmaceutical industry. Initially, Nb2O5, Cr2O3 and Zn(II)-Cr(III) mixed oxide have been developed, besidesthe heteropoli acid supported on SiO2 and their respective cesium salt. The morphological properties such as surface area, diameter and pore volume, and the acidic properties of materials, such as nature and strength, were evaluated looking for a correlation between thesolid structure and catalytic properties thereof. The mixed oxide and the metal oxides produced were used in the Nopol synthesis byPrins condensations of -pinene with paraformaldehyde. The acidbase properties of Zn-Cr oxide is believed to be responsible for its catalytic efficiency. The results obtained indicate that metal oxides are promising environmentally benign catalysts for the Prins condensationof biorenewable feedstocks Silica-supported H3PW12O40 and its acidic Cs salt (Cs2,5H0,5PW12O40) are efficient, environmentally benign and versatile heterogeneous catalysts for the liquid-phaseisomerization of limonene oxide, and gives dihydrocarvone as the main product. Furthermore, these materials can be used also for the cycloaddition of crotonaldehyde to monoterpenic alkenes (as limonene, -pinene and -pinene) giving the same oxabicyclo[3.3.1]nonenecycloaddition product. These reactions occurs under mild conditions at low catalyst loadings without heteropoly acid leaching into the liquid phase. Finally, gold nanoparticles supported in MgO were found to be an effective heterogeneous catalyst for the liquid-phase oxidation of a wide range of alcohols with molecular oxygen in the absence of any co-catalyst or additive. In addition, the Au/MgO catalyst performs the one-pot base-free aerobic oxidative esterification of benzyl alcoholexhibiting high activity, selectivity to methyl benzoate and stability. The oxidation of various biomass-based monoterpenic alcohols over the Au/MgO catalyst resulted in carbonylic terpenoids, useful for fragrance and pharmaceutical industries, in good to excellent yields,more than 80% in some cases.