Navegando por Autor "Kozhevnikov, Ivan V."
Agora exibindo 1 - 13 de 13
Resultados por página
Opções de Ordenação
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 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.Item Phosphotungstic heteropoly acid as efficient heterogeneous catalyst for solvent-free isomerization of a-pinene and longifolene.(2009) Rocha, Kelly Alessandra da Silva; Robles Azocar, Patrícia Alejandra; 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 a-pinene and longifolene into their more valuable isomers – camphene and isolongifolene, respectively, which are intermediates in the synthesis of expensive fragrances. The reactions occur under solvent-free conditions in the temperature range of 80–100 8C, with low catalyst loadings (0.15–5 wt%) and high turnover numbers (up to 6000 per proton). The catalyst can be easily recovered and reused. No PW leaching is observed in the reaction system.