Hidroformilação de monoterpenos para-mentênicos catalisada por complexos de ródio

Exportado OPUSMade available in DSpace on 2019-08-14T05:29:42Z (GMT). No. of bitstreams: 1 disserta__o_de_mestrado___completa.pdf: 7055699 bytes, checksum: 5772de0e288f5b342381cb1e51915bad (MD5) Previous issue date: 14O presente trabalho relata os resultados encontrados para a hidroformilação do terpinoleno catalisada por complexo de ródio em condições reacionais brandas e na presença de um ligante fosforado. Uma escolha adequada dessas condições permite a hidroformilação relativamente rápida desse substrato e seletividade conjunta para três aldeídos principais de até 85% na conversão próxima de 90%. Essa mistura de aldeídos pode ser usada em fragrâncias, pois apresenta propriedades organolépticas agradáveis. Os aldeídos obtidos foram identificados e caracterizados por CG-EM, RMN de 1H, de 13C, DEPT, NOESY, COSY e HMQC. Os resultados obtidos indicam que a hidroformilação da ligação endocíclica do terpinoleno só foi possível devido a propriedade especial do tris(o-tercbutilfenil)fosfito, visto que apenas um ligante coordena-se ao centro metálico, permitindo assim que a olefina também se ligue ao mesmo. Resultados pouco expressivos foram encontrados quando o ligante usado foi a PPh3, nas mesmas condições reacionais.This paper reports the results on the rhodium catalyzed hydroformylation of terpinolene under milder reaction conditions and in the presence of a phosphorous ligand. An appropriate choice of these conditions allows a relatively rapid hydroformylation of the substrate with a combined selectivity for three main aldehydes of up to 85% at 90% conversion. The mixture of these aldehydes can be used in fragrance compositions due to its pleasant organoleptic properties. The aldehydes were identified and characterized by GC-MS, NMR of 1H, of 13C, DEPT, NOESY, COSY and HMQC. The results indicate that the hydroformylation of the endocyclic double bond in terpinolene is only possible because of the special properties of tris(o-tercbutylphenyl)phosphite. Due to the large cone angle of this ligand, catalytically active monoligand rhodium species predominate in the reaction solutions even at high P/Rh ratios allowing the coordination of the sterically encumbered olefin. Much more modest results were found when PPh3 was used as an auxiliary ligand under the same reaction condition

Synthesis of fragrance compounds from acyclic monoterpenes : rhodium catalyzed hydroformylation and tandem hydroformylation/acetalization of linalool and B-citronellene.

Rhodium-catalyzed hydroformylation of acyclic monoterpenic compounds, i.e., linalool and _- citronellene, was studied in toluene and ethanol solutions in the presence of PPh3 or P(O-o-tBuPh)3 ligands. Although both substrates have a monosubstituted terminal double bond, they show different behavior under the hydroformylation conditions. In toluene, linalool gave almost quantitatively a cyclic hemiacetal; whereas the hydroformylation of _-citronellene resulted in two isomeric aldehydes also in a nearly quantitative combined yield. The reactions occurred approximately two times faster in ethanol than in toluene giving the corresponding acetals even in the absence of additional acid co-catalysts. In the absence of phosphorous ligands, linalool (differently from _-citronellene) was very resistant to hydroformylation probably due to the binding with rhodium through both the double bond and the hydroxyl group to form stable chelates. The P(O-o-tBuPh)3 ligand exerted a remarkable effect on the reactivity of both substrates accelerating the reactions by 5–20 times as compared to the system with PPh3. Several fragrance compounds were obtained in high yields through a simple one-pot procedure starting from the substrates easily available from natural bio-renewable resources

Synthesis of fragrance compounds from biorenewables : tandem hydroformylation–acetalization of bicyclic monoterpenes.

The 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

Sulfonated polystyrene: A catalyst with acid and superabsorbent properties for the esterification of fatty acids

In this work, catalysts with acid and superabsorbent properties were obtained by sulfonation of expanded polystyrene and used to promote the esterification of oleic acid with ethanol. The prepared superabsorbent polymers (SAP) showed high concentration of active sulfonic acid sites (0.7–5.9 mmol acid sites g−1) and high water absorption capacity (445–900 gwater g−1). It was observed that the catalytic activity increased with the number of acid site and water absorption capacity. Turnover frequencies suggested that the catalytic activity depends on the accessibility/diffusion processes determined by the crosslinks in the polymer. Commercial sulfonic acid resins and polyacrylate based superabsorbent polymers showed very low activities compared with the SAP produced. The SAP also showed higher activity compared to the homogeneous catalyst p-toluenesulfonic acid. The higher activity of the prepared SAP is discussed in terms of the acidity of sulfonic groups combined with the water absorption which shifts the esterification equilibrium

Synthesis of fragrance compounds from renewable resources : the aqueous biphasic hydroformylation of acyclic terpenes.

The rhodium-catalyzed hydroformylation of acyclic terpenic compounds, i.e., ?-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 ?-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

Syntheses, structural and spectroscopic characterization of novel zinc(II)-bis(trithiocarbimato) complexes and bis(N-methylsulfonyldithiocarbimate)-sulfide.

Four zinc(II)-bis(trithiocarbimato) complexes with the general formula A2[Zn(RSO2N@CS3)2] [A= Ph4P+: R = CH3 (1), 4-CH3C6H4 (2); A = Bu4N+: R = CH3 (3), 4-CH3C6H4 (4)] were obtained by the reaction of sulfur with the correspondent zinc(II)-bis(dithiocarbimato) complexes. Additionally, the compound (Ph4P)2[(CH3SO2N@CS2)2S)] (5) was prepared from the potassium methylsulfonildithiocarbimate by oxidation with iodine. The compounds were characterized by elemental analyses and IR, 1H NMR and 13C NMR spectroscopies. The compounds 4 and 5 were also characterized by X-ray diffraction techniques. The compound 4 crystallizes in the centrosymmetric space group C2/c of the monoclinic system. The Zn(II) is in a distorted tetrahedral environment (ZnS4) in compound 4, and differ from the coordination mode observed in compound 1, which involves one sulfur and one nitrogen atom of each trithiocarbimate ligand. Compound 5 is the first example of a compound containing a bis(N-alkylsulfonyldithiocarbimate)-sulfide dianion and crystallises in the non-centrosymmetric space group P41212 of the tetragonal system

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora