Navegando por Autor "Freitas, Marina Caneschi de"
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Item Synthesis of fragrance compounds from biorenewables : tandem hydroformylation–acetalization of bicyclic monoterpenes.(2013) Freitas, Marina Caneschi de; Vieira, Camila Grossi; Santos, Eduardo Nicolau dos; Gusevskaya, Elena VitalievnaThe Rhodium-catalyzed tandem hydroformylation–acetalization of the terpenes 3-carene, 2-carene, a-pinene, and b-pinene was studied in ethanol solutions in the presence of PPh3 or tris(O-tert-butylphenyl)phosphate, P(O-o-tBuPh)3, ligands. All these terpenes are constituents of turpentine oils obtained commercially from coniferous trees. b-Pinene gave the corresponding aldehyde and acetal in excellent combined yields in both systems. 3-Carene, 2-carene, and a-pinene, which contain sterically encumbered endocyclic double bonds, showed an extremely low reactivity with PPh3. The use of P(O-o-tBuPh)3 not only accelerated the hydroformylation of all four substrates remarkably but also increased the acetalization activity of the catalyst. In the Rh/P(O-o-tBuPh)3 system, various fragrance acetals and aldehydes were obtained from these renewable substrates in nearly quantitative combined yields. The process was performed under mild conditions, in environmentally friendly ethanol as a solvent, and in the absence of acid cocatalysts.Item Synthesis of fragrance compounds from renewable resources : the aqueous biphasic hydroformylation of acyclic terpenes.(2015) Vieira, Camila Grossi; Freitas, Marina Caneschi de; Oliveira, Kelley Cristina Batista de; Faria, Amanda de Camargo; Santos, Eduardo Nicolau dos; Gusevskaya, Elena VitalievnaThe rhodium-catalyzed hydroformylation of acyclic terpenic compounds, i.e., β-citronellene, linalool and nerolidol, was performed in a water/toluene biphasic system. The addition of the cationic surfactant cetyltrimethylammonium chloride remarkably increased the reaction rates, with the surfactant effect being substrate dependent. A water-soluble phosphine ligand was used to immobilize the rhodium catalyst in water, an environmentally benign solvent, whereas non-polar products were collected in the organic phase. A complete phase separation was easily achieved by switching the magnetic stirrer off and cooling the mixture to room temperature. Linalool and nerolidol gave cyclic hemiacetals with excellent stereoselectivity, whereas the hydroformylation of β-citronellene resulted in two isomeric aldehydes with a linear-to-branched product ratio of approximately 85/15. Several fragrance compounds with pleasant sweet floral and woody scents were obtained in high yields through a simple and green one-pot procedure starting from the substrates easily available from natural bio-renewable resources.