Navegando por Autor "Rocha, Kelly Alessandra da Silva"
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Item Aplicação de catalisadores a base de heteropoliácidos na transformação de compostos terpênicos : (+)-aromadendreno e (R,R)-sabineno.(2019) Ribeiro, Maria Stella Palhares; Rocha, Kelly Alessandra da Silva; Vieira, Camila Grossi; Rocha, Kelly Alessandra da Silva; Robles Azocar, Patrícia Alejandra; Rosmaninho, Marcelo GonçalvesNeste trabalho foram empregados catalisadores a base de heteropoliácidos da série de Keggin, no desenvolvimento de processos para transformação catalítica de componentes presentes na matéria prima de origem natural, visando obter compostos com potencial valor agregado. Estudou-se a aplicação do catalisador H3PW12O40 (PW), o heteropoliácido mais forte da série Keggin, em sistema homogêneo, e seu sal de césio (CsPW), empregado como catalisador em sistema heterogêneo, para a funcionalização do (+)-aromadendreno em fase líquida. Até então, não foi encontrado relatos na literatura usando heteropoliácidos como catalisadores para essa reação. O (+)-aromadendreno é um composto de origem natural, o qual pode ser extraído da cauda de destilação do óleo essencial de Eucalyptus globulus, e cuja principal propriedade é atividade antimicrobiana. Os estudos da transformação de (+)-aromadendreno resultaram na obtenção de produtos funcionalizados conhecidos e inéditos, além do produto de isomerização formado nos solventes butanol e etanol, conhecido como (+)-ledeno, que apresenta propriedades antibacteriana, antifúngica, ant-inflamatória e anti-oxidante, empregados principalmente na indústria farmacêutica. A seletividade para os produtos de interesse é dependente das condições reacionais, contudo, foram observados a formação dos mesmos produtos principais mediante o uso do PW e do CsPW para ambos os solventes estudados. A utilização do etanol como solvente e nucleófilo se mostrou mais promissora quando comparada ao emprego do butanol. O uso do catalisador heterogêneo, CsPW, possibilita o desenvolvimento de um processo ambientalmente favorável, onde a recuperação do catalisador pode ocorrer mais facilmente assim como sua reutilização. Em condições otimizadas e na presença de CsPW, foi alcançado um rendimento de 70%, em apenas 30 minutos de reação em butanol. E em etanol um rendimento conjunto para os produtos de interesse equivalente a 74%. O CsPW também foi utilizado como catalisador em sistema heterogêneo na isomerização e na funcionalização do (R,R)-sabineno. Até o presente momento, não existem relatos de estudos empregando catalisadores a base de sal de heteropoliácido para esta finalidade, sendo inédita a aplicação do sal CsPW na reação proposta. O sabineno é um monoterpeno bicíclico encontrado no óleo essencial da planta Aloysia sellowii moldenke, na pimenta preta e também em de folhas do grupo Duguetia furfuracea. Esse composto apresenta ação analgésica, anti-inflamatória e expectorante. Em todos os testes catalíticos realizados, foram obtidos como produtos principais os compostos: α-terpineno, γ-terpineno, terpinoleno, acetato de 1,4-terpineol, 1,4-terpineol e 1,8-terpineol. Em condições favoráveis a funcionalização do (R,R)-sabineno foi possível obter seletividade de 12% para α-terpineno, 17% para γ-terpineno, 4% para terpinoleno, 13% para acetato de 1,4-terpineol, 13% para 1,4-terpineol e 17% para 1,8-terpineol. Esses resultados estão atrelados a conversões significativas do substrato, de aproximadamente 95%. Todos os compostos obtidos apresentam aplicação conhecida na indústria da química fina.Item Avaliação da atividade e seletividade de compósitos mesoporosos de MCM-41 e CuO no processo de fotorredução de CO2.(2022) Ceron Geovo, Jose David; Nogueira, André Esteves; Nogueira, André Esteves; Olortiga Asencios, Yvan Jesus; Rocha, Kelly Alessandra da SilvaA conversão de CO2 em valiosa matéria-prima química por meio da fotocatálise é considerada uma estratégia interessante para mitigar o aquecimento global e os problemas de fornecimento de energia. O principal desafio na fotorredução de CO2 é projetar e sintetizar fotocatalisadores ativos com boa absorção de luz visível, com grande afinidade pela molécula de CO2 e com potencias de redução da banda de condução (BC) adequados para promover a redução das moléculas de CO2. Nesse sentido, as peneiras moleculares com nanopartículas de óxido metálico, como o óxido de cobre (CuO), mostram-se como alternativas a substituição dos semicondutores tradicionais (TiO2 e ZnO), pois apresentam propriedades como elevada capacidade de adsorção de CO2 e elevada área de contato entre o catalisador, tornando-os candidatos promissores para serem usados em reações fotocatalíticas. Desta forma, o trabalho teve como objetivo o desenvolvimento de fotocatalisadores a base de MCM-41 e óxido de cobre (CuO) e avaliar a sua atividade e a seletividade no processo de fotorredução de CO2 sob radiação UV. Os compósitos foram sintetizados por dois processos de síntese distintos (método de impregnação do sal e o método de coprecipitação) e caracterizado utilizando diferentes técnicas. Através das caracterizações realizadas, observou-se que os dois métodos de síntese utilizados possibilitaram a formação dos compósitos com uma elevada área superficial e com uma energia de band gap na região do visível (espectro eletromagnético). Além disso, verificou-se que a MCM-41 pura e o compósito MCM-41/CuO possuem relevante potencial para aplicação no processo de fotorredução de CO2, no qual a composição e os diferentes sítios ativos presentes na superfície dos fotocatalisadores desempenharam um papel crítico na atividade e seletividade dos produtos formados. Os resultados mostraram que o MCM-41 e o compósito com 1% (p/p%) de CuO (MCM-41/CuO 1%) obtidos pelo método de impregnação apresentaram alta seletividade e produção de metanol, com 585,88 e 267,05 μmol.gcat.-1 respectivamente. Assim, os resultados demonstraram a versatilidade do MCM-41 para formar compósitos com semicondutores, bem como a necessidade de compreender os principais aspectos que influenciam a fotorredução de CO2 e a seletividade dos compósitos, incluindo suas características superficiais, estruturais e elétricas.Item Catalytic transformations of (+)-aromadendrene : functionalization and isomerization reactions in the presence of the heteropoly acid catalyst H3PW12O40.(2020) Ribeiro, Maria Stella Palhares; Santos, Caroline de Souza; Vieira, Camila Grossi; Rocha, Kelly Alessandra da SilvaTransformations of the naturally occurring compound (+)-aromadendrene (1) were performed in the presence of the heteropoly acid catalyst H3PW12O40, a technologically efficient homogeneous catalyst, which, in principle, can be recovered from polar solutions by precipitation using a nonpolar solvent. In solutions of n-butanol and ethanol, there was the formation of (+)-ledene resulting from isomerization of the double bond in the carbon chain of the substrate and the ether produced by nucleophilic addition of the alcohol molecule to the exocyclic double bond of 1. In ethanol solution, in addition to formation of (+)-ledene and the ether product derived from ethanol, there was also the formation of a product formed by the addition of a water molecule to the (+)-aro madendrene double bond. The products, alone or mixed, presented pharmacological properties and have the potential for commercial application. The simple catalytic process developed in this work is a technologically attractive route, which employs a renewable substrate for the production of compounds with potential uses in the fine chemical industry.Item Cobalt-catalyzed oxidation of terpenes : Co-MCM-41 as an efficient shape-selective heterogeneous catalyst for aerobic oxidation of isolongifolene under solvent-free conditions.(2009) Robles Azocar, Patrícia Alejandra; Rocha, Kelly Alessandra da Silva; Sousa, Edésia Martins Barros de; Gusevskaya, Elena VitalievnaCobalt-containing MCM-41 was used as a heterogeneous catalyst for the liquid-phase aerobic oxidation of isolongifolene, one of the most available sesquiterpenes. The material was prepared by direct incorporation of cobalt into the framework through the hydrothermal method, and was characterized by ICPAES, N2 adsorption–desorption, TEM, XRD, SAXS, XPS, and H2-TPR techniques. Characterizations suggest that cobalt introduced into MCM-41 exists mainly in a single-site Co2+ state, whereas the amounts of the extraframework Co3O4 are relatively low. The oxidation of isolongifolene under mild solvent-free conditions results mainly (90% selectivity) in isolongifolen-9-one, a compound which occupies a vintage place in modern perfume industry. The total concentration of oxygenated products in the final mixtures reaches 90 wt%. The catalyst undergoes no metal leaching, and can be easily recovered and re-used. A silica- included cobalt catalyst prepared through a conventional sol–gel method shows a catalytic activity comparable with that of Co-MCM-41; however, selectivity is much lower.Item Complexos heterolépticos de cobre (II) com 2-hidroxibenzofenonas e diiminas : síntese, caracterização e investigação de suas propriedades biológicas.(2022) Rodrigues, Júlia Helena Valadares; Correa, Rodrigo de Souza; Oliveira, Katia Mara de; Correa, Rodrigo de Souza; Oliveira, Katia Mara de; Teixeira, Leonardo César de Moraes; Rocha, Kelly Alessandra da SilvaNo presente trabalho obteve-se e caracterizou-se quatro novos complexos de cobre (II) identificados como [Cu(bipy)(2H4MeBz)]NO3 (1), [Cu(fen)(2H4MeBz)]NO3 (2), [Cu(bipy)(2H4OcBz)]NO3 (3) e [Cu(fen)(2H4OcBz)]NO3 (4), onde bipy é 2,2’-bipiridina, fen é 1,10-fenantrolina, 2H4MeBz significa 2-hidroxi-4-metoxibenzofenona e (2H4OcBz) presenta o ligante 2-hidroxi-4-(octiloxi)benzofenona. Os compostos foram sintetizados e caracterizados por meio de análise elementar, condutimetria, temperatura de decomposição, por técnicas espectroscópicas e espectrométricas, como espectroscopia de absorção na região do infravermelho e do ultravioleta e visível e espectrometria de massas, bem como por difração de raios X de monocristal, para o caso do complexo 2 via substituição do ligante nitrato (NO3 - ) pelo ligante perclorato (ClO4 - ). A atividade citotóxica dos complexos 1-4 foi investigada frente às linhagens celulares tumorais HCT116 (carcinoma de cólon humano) e HepG2 (carcinoma hepatocelular humano) e não tumoral MRC-5 (fibroblasto de pulmão humano). Os complexos foram citotóxicos frente a todas as linhagens celulares estudadas, apresentando valores de IC50 na faixa de 3,38μM – 64,9μM para as linhagens tumorais e para a linhagem celular não tumoral, MRC-5 os valores de IC50 variaram de 4,65 μM a 50,22 μM. Além disso o índice de seletividade para células tumorais variou de 0,77 a 1,42. Estes resultados indicam que complexos de cobre (II) 2 e 4 provaram ser mais citotóxicos que os demais complexos e foram mais seletivos para as células tumorais que a oxaliplatina. Interações dos complexos com macromoléculas [CT-DNA (DNA Calf-Thymus) e BSA (Albumina do soro bovino)] foram avaliadas para melhor compreender o mecanismo de ação dos complexos. Por fim, observou-se que os complexos contendo ligante 1,10-fenantrolina exibiram citotoxicidades mais promissoras que os complexos contendo 2,2’-bipiridina, podendo ser explorados com mais detalhes e estudos in vitro e in vivo.Item Coupling of monoterpenic alkenes and alcohols with benzaldehyde catalyzed by silica-supported tungstophosphoric heteropoly acid.(2017) Cotta, Rafaela Ferreira; Rocha, Kelly Alessandra da Silva; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaThe reactions of biomass-based substrates, i.e., limonene, -pinene, -pinene, terpinolene, -terpineol,nerol and linalool, with benzaldehyde in the presence of tungstophosphoric heteropoly acid H3PW12O40(HPW) supported on silica give an oxabicyclo[3.3.1]nonene compound with fragrance characteristics ingood to excellent yields. The reactions apparently involve the formation of -terpenyl carbenium ion bythe protonation of alkene or dehydration of alcohol followed by the nucleophilic attack of benzaldehyde.The subsequent oxonium-ene cyclization of the resulting oxocarbenium ion gives the oxabicyclic product.The process is an environmentally benign and heterogeneous and can be performed under mild conditionswith low catalyst amounts and no significant leaching of active components.Item Coupling of phenylacetaldehyde and styrene oxide with biorenewable alkenes in eco-friendly solvents.(2021) Cotta, Rafaela Ferreira; Martins, Rafael Araújo; Rocha, Kelly Alessandra da Silva; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaAcidic cesium salt of tungstophosphoric heteropoly acid, Cs2.5H0.5PW12O40 (CsPW), is an excellent solid acid catalyst for the reaction of phenylacetaldehyde with biorenewable monoterpenic alkenes: limonene, α-terpineol, α-pinene and β-pinene. Simultaneously with a conventional oxonium-ene cyclization to give an oxabicyclo[3.3.1] nonene compound, phenylacetaldehyde undergoes Friedel-Crafts alkylation by the monoterpenes resulting in a new product with an unusual fused tetracyclic structure, obtained in ca. 80 % yield. A combined yield for both products was up to 95 %. Styrene oxide can be also used as a starting material for these reactions to give the same products in up to 85 % combined yield. A novel one-pot tandem process thus developed involves the isomeri- zation of styrene oxide into phenylacetaldehyde and cycloaddition of the latter to the monoterpene, with both steps being catalyzed by CsPW. The reactions were performed in green solvents diethylcarbonate or anisole, which have high sustainability ranks in modern solvent selection guides, comparable to those of ethanol and water.Item Esterification of camphene over heterogeneous heteropoly acid catalysts : synthesis of isobornyl carboxylates.(2011) Meireles, Augusto Luís Pereira de; Rocha, Kelly Alessandra da Silva; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaSilica supported H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an active and environmentally friendly solid acid catalyst for liquid-phase esterification of camphene, a renewable biomass-based substrate, with C2, C4 and C6 short-chain fatty acids. The reaction provides isobornyl carboxylates, useful as fragrances, in virtually 100% selectivity and 80–90% yield. The reaction is equilibrium-controlled and occurs under mild conditions with a catalyst turnover number of up to 3000. The use of hydrocarbon solvent prevents PW from leaching to allow easy catalyst recovery. The catalyst can be reused several times without loss of activity and selectivity.Item Heteropoly acid catalysis for the isomerization of biomass-derived limonene oxide and kinetic separation of the trans-isomer in green solvents.(2019) Cotta, Rafaela Ferreira; Martins, Rafael; Pereira, Matheus Mello; Rocha, Kelly Alessandra da Silva; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaTerpenes are an abundant class of natural products, which is important for flavor and fragrance industry. Many acid catalyzed reactions used for upgrading terpenes still involve mineral acids as homogeneous catalysts and/or toxic solvents. Heteropoly acids represent a well-established eco-friendly alternative to conventional acid catalysts. As these reactions are usually performed in the liquid phase, solvents play a critical role for the process sustainability. In the present work, we developed a catalytic route to valuable fragrance ingredients, dihydrocarvone and carvenone, from limonene oxide by its isomerization using silica-supported tungstophosphoric acid as a heterogeneous catalyst and dialkylcarbonates as green solvents. The reaction pathway can be switched between dihydrocarvone and carvenone (obtained in 90% yield each) simply by changing the reaction temperature. In addition, we developed an efficient method for kinetic separation of trans-limonene oxide from commercial cis/trans-limonene oxide mixture and stereoselective synthesis of trans-dihydrocarvone.Item Heteropoly acid catalysts for the synthesis of fragrance compounds from bio-renewables : acetylation of nopol and terpenic alcohols.(2016) Costa, Vinícius Vieira; Rocha, Kelly Alessandra da Silva; Oliveira, Luiz Carlos Alves de; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaThe cesium salt of tungstophosphoric heteropoly acid, Cs2.5H0.5PW12O40, is an active and environmentally friendly heterogeneous catalyst for the liquid-phase acetylation of nopol and several biomass-derived terpenic alcohols (i.e., a-terpineol, nerol, geraniol, linalool, menthol, isoborneol, perillyl alcohol, carveol, isopulegol, carvacrol and nerolidol) with acetic anhydride. The resulting flavor and fragrance acetic esters, which are widely used in perfumery, household and food products, are obtained in good to excellent yields. The reactions occur at room temperature with low catalyst loadings without substantial catalyst leaching and can be performed with stoichiometric amounts of an acetylating agent in solvent free systems.Item Heteropoly acid catalysts for the synthesis of fragrance compounds from biorenewables : isomerization of limonene oxide.(2013) Costa, Vinícius Vieira; Rocha, Kelly Alessandra da Silva; Kozhevnikov, Ivan V.; Kozhevnikova, Elena Fedorovna; Gusevskaya, Elena VitalievnaThe liquid-phase isomerization of limonene oxide was studied in the presence of heteropoly acid catalysts in aprotic solvents in homogeneous and heterogeneous systems. Among the catalysts were bulk and silica-supported tungstophosphoric acid H3PW12O40 and its acidic Cs salt Cs0.5H0.5PW12O40 (CsPW). The reaction gave dihydrocarvone, a valuable fragrance intermediate, as the main product with turnover numbers of up to 8000. The nature of the solvent had a strong effect on reaction rate and selectivity. CsPW (0.1 mol%) was found to be a highly efficient and truly heterogeneous catalyst for this reaction, providing 82% yield of dihydrocarvone in 1,4-dioxane as a solvent under ambient conditions. This simple catalytic method represents economically attractive route to industrially important compounds starting from bio-renewable substrates easily available from essential oils.Item Heteropoly acid catalysts for the synthesis of fragrance compounds from biorenewables : the alkoxylation of monoterpenes.(2014) Meireles, Augusto Luís Pereira de; Costa, Maíra dos Santos; Rocha, Kelly Alessandra da Silva; Gusevskaya, Elena Vitalievna; Kozhevnikov, Ivan V.The cesium salt of tungstophosphoric heteropoly acid, Cs2.5H0.5PW12O40, is an active and environmentally friendly solidacid catalyst for the liquid-phase alkoxylation of widespread monoterpenes, such as camphene, limonene, a-pinene, and bpinene. These reactions provide isobornyl or a-terpenyl ethers, useful as fragrances, in good to excellent yields. The reactions are equilibrium-controlled and occur with high catalyst turnover numbers (TONs) up to 1500–4200 without catalyst leaching. Heteropoly acid H3PW12O40 also efficiently catalyzes the alkoxylation of these monoterpenes under homogeneous conditions with TONs up to 1500–11 300.Item Heteropoly acid catalysts in Prins cyclization for the synthesis of Florol.(2021) Meireles, Augusto Luís Pereira de; Rocha, Kelly Alessandra da Silva; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaH3PW12O40 heteropoly acid supported on SiO2 and its bulk acidic cesium salt Cs2.5H0.5PW12O40 are demonstrated to be highly active and recyclable solid catalysts for Prins cyclization allowing for the clean, high-yielding synthesis of Florol® from isoprenol and isovaleraldehyde. Florol®, a valuable floral odorant employed in a vast variety of commercial products, was obtained in ca. 80 % yield under nearly ambient conditions. Dime- thylcarbonate or diethylcarbonate used as green reaction media, low catalyst loadings and moderate conditions are important features that contribute for the sustainability of the method.Item Heteropoly acid catalysts in the valorization of the essential oils : acetoxylation of b-caryophyllene.(2010) Rocha, Kelly Alessandra da Silva; Rodrigues, Nathália V. S.; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaH3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an active and environmentally friendly catalyst for the liquid-phase conversion of b-caryophyllene (1) to b-caryolanyl acetate (2) in homogeneous and heterogeneous systems. An efficient and clean method for the synthesis of 2, providing amixture containing two stereoisomeric b-caryolanyl acetates 2a and 2b, 2a/2b = 80/20 mol/ mol, with 100% GC yield, has been developed using PW as a homogeneous catalyst under mild reaction conditions. The reaction occurs at 25 8C with a catalyst turnover number of 2000. The catalyst can be recovered without neutralization and reused without loss of activity and selectivity.Item Heteropoly acid catalysts in upgrading of biorenewables : cycloaddition of aldehydes to monoterpenes in green solvents.(2017) Cotta, Rafaela Ferreira; Rocha, Kelly Alessandra da Silva; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaAcidic Cs salt of tungstophosphoric heteropoly acid, Cs2.5H0.5PW12O40 (CsPW), is excellent solid acid catalyst for liquid-phase cycloaddition reactions of biomass-based and easily available from essential oils monoterpenic compounds, such as limonene, α-terpineol, α-pinene, β-pinene and nerol, with aldehydes, including benzaldehyde, crotonaldehyde as well as biomass-derived cuminaldehyde and trans-cinnamaldehyde. The reactions give oxabicyclo[3.3.1]nonene compounds potentially useful for the fragrance and pharmaceutical industries in good to excellent yields. The process is environmentally benign and can be performed in biomass-derived solvent 2-methyltetrahydrofuran and eco-friendly “green” organic solvents such as dimethylcarbonate and diethylcarbonate under mild conditions at low catalyst loadings without leaching problems. The solid CsPW catalyst can be easily separated from the reaction media and low-boiling solvents can be removed by distillation. Silica-supported H3PW12O40 also demonstrated good performance in these reactions.Item Heteropoly acid catalysts in upgrading of biorenewables : synthesis of para-menthenic fragrance compounds from α-pinene oxide.(2020) Ribeiro, Cláudio Júnior Andrade; Pereira, Matheus Mello; Kozhevnikova, Elena Fedorovna; Kozhevnikov, Ivan V.; Gusevskaya, Elena Vitalievna; Rocha, Kelly Alessandra da SilvaThe isomerization of α-pinene oxide in the presence of Cs2.5H0.5PW12O40 (CsPW) heteropolysalt as solid acid catalyst is reported. The reactions were performed in various solvents, which allowed to obtain trans-carveol, trans-sobrerol and pinol in 60–80% yield each, which exceed the yields reported so far. The CsPW catalyst could be recovered and reused without loss of its activity and selectivity.Item Heteropoly acid catalyzed cyclization of nerolidol and farnesol : synthesis of bisabolol.(2015) Meireles, Augusto Luís Pereira de; Costa, Maíra dos Santos; Rocha, Kelly Alessandra da Silva; Gusevskaya, Elena VitalievnaHeteropoly acid H3PW12O40 is an active and environmentally friendly homogeneous catalyst for the synthesis of _-bisabolol, a high-priced and highly demanded ingredient for the fragrance, cosmetic and pharmaceutical industries, starting from more abundant biomass-based sesquiterpenic alcohols. The solvent nature remarkably affects the reaction pathways and product selectivity. In acetone solutions, _-bisabolol can be obtained in 55–60% GC yields from nerolidol and 60–70% GC yields from farnesol at complete substrate conversions, which are probably the best results ever reported for these reactions. _-Bisabolol synthesized by this method contains no farnesol, which is a potentially allergenic compound and should be avoided in the commercially used _-bisabolol. This advantage is especially important because the distillative separation of _-bisabolol and farnesol is a troublesome task. The catalyst shows high turnover numbers and operates under mild nearly ambient conditions.Item Heteropoly acid-catalyzed β-caryophyllene chemical transformations : synthesis route of value-added commercial products from components found in biorenewable resources.(2023) Silva, Marcelly Maurício Brandão; Vieira, Camila Grossi; Rocha, Kelly Alessandra da SilvaMore sustainable catalytic processes applied to different reactions for of biorenewable derivatives production is an important trend in chemical industry, which constantly needs to update its processes for obtaining inputs not produced in sufficient quantity by nature, or with superior physicochemical properties to those of compounds acquaintances. This work reports the chemical transformation of β-caryophyllene, a sesquiterpene present in biorenewable materials, using the commercial heteropoly acid catalyst H3PW12O40. The process performed under conditions technologically and environmentally attractive, using less harmful ketone solvents (2-butanone and acetone). The products obtained were (-)-clovene, β-caryolanol and β-clovanol, at total yield 70–80%, by isomerization reaction associated with hydration reactions. All these products have known applications in different sectors of the fine chemicals industry, whether in isolated forms or as mixtures. (-)-Clovene and β-caryolanol have significantly higher commercial value, compared to β-caryophyllene. There are known applications for β-clovanol, although the compound has not yet been commercialized, making the process described here attractive for its production on an industrial scale. H3PW12O40 showed catalytic performance superior to H2SO4, a conventional mineral acid catalyst.Item Isomerization of a-pinene oxide over cerium and tin catalysts : selective synthesis of trans-carveol and trans-sobrerol.(2011) Costa, Vinícius Vieira; Rocha, Kelly Alessandra da Silva; Sousa, Líniker Fabrício de; Robles Azocar, Patrícia Alejandra; Gusevskaya, Elena VitalievnaA remarkable effect of the solvent nature on the acid catalyzed transformation of _-pinene oxide allowed direction of the reaction to either trans-carveol or trans-sobrerol. Each of these highly valuable compounds was obtained in nearly 70% yield using an appropriate polar solvent, whose basicity affected strongly the product distribution. In acetone, a weakly basic solvent, the reaction over heterogeneous sol–gel Sn/SiO2 or Ce/SiO2 catalysts gave mainly trans-sobrerol. No leaching of active components occurs under the reaction conditions and the catalysts can be recovered and reused. On the other hand, in more basic solvent, i.e., dimethylacetamide, the reaction was essentially directed to trans-carveol. Due to the leaching problems with Sn/SiO2 and Ce/SiO2 materials, the synthesis of trans-carveol was performed under homogeneous conditions using CeCl3 or SnCl2 as catalysts with a catalyst turnover number up to ca. 1200. The method represents one of the few examples of the synthesis of isomers from _-pinene oxide, other than campholenic aldehyde, with a sufficient for practical usage selectivity.Item Isomerization of styrene oxide to phenylacetaldehyde over supported phosphotungstic heteropoly acid.(2010) Costa, Vinícius Vieira; Rocha, Kelly Alessandra da Silva; Kozhevnikov, Ivan V.; Gusevskaya, Elena VitalievnaSilica-supported H3PW12O40 (PW), the strongest heteropoly acid in the Keggin series, is an efficient, environmentally friendly heterogeneous catalyst for the liquid-phase isomerization of styrene oxide into phenylacetaldehyde, an industrially important intermediate for fine chemical synthesis. The reaction occurs in cyclohexane as a solvent under mild conditions at 25–70 ◦C with low catalyst loadings and without PW leaching in solution. At 60 ◦C, the yield of phenylacetaldehyde reaches 92% at 97% styrene oxide conversion, with a catalyst turnover number of 19 600. The catalyst can be recovered and reused.