- Methoxylation of α-pinene over heteropolyacids immobilized in silica
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The methoxylation of α-pinene was studied using heteropolyacids immobilized on silica as catalysts, at 60 °C, being the α-terpinyl methyl ether the main product. Tungstophosphoric acid (PW), molybdophosphoric acid (PMo), tungstosilicic acid (SiW) and molybdosilicic acid (SiMo) were immobilized on silica by sol-gel method. It was observed that the catalytic activity of the silica-supported heteropolyacids decreases in the series: PW2_S > SiW_S > PMo_S > SiMo_S. A series of PW immobilized on silica with different PW loading were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized on silica. However, at high amount of PW on silica, a decrease of the catalytic activity was observed. Good values of selectivity to α-terpinyl methyl ether (about 60% near complete conversion) were obtained with all catalysts. Catalytic stability of the PW2_S was evaluated by performing consecutive batch runs with the same catalyst sample. After the third batch it was observed a stabilisation of the initial activity. A kinetic model was developed assuming that the α-pinene is consumed according to the parallel reaction network. It was observed that the kinetic model fits the experimental concentration data quite well.
- Pito,Matos,Fonseca,Ramos,Vital,Castanheiro
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p. 140 - 146
(2010/10/01)
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- Trimethylsilyldiazomethane - A mild and efficient reagent for the methylation of carboxylic acids and alcohols in natural products
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Esterification of various naturally occurring carboxylic acids with trimethylsilyldiazo-methane proceeds nearly quantitatively under very mild conditions. Furthermore, highly sterically hindered alcohols can be converted directly to the corresponding methyl ethers. Improved methods for the preparation and quantification of this reagent are described. Springer-Verlag 2004.
- Presser, Armin,Huefner, Antje
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p. 1015 - 1022
(2007/10/03)
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- Acid-catalyzed alkoxylation and hydration of camphene
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Camphene alkoxylation in the presence of various acid catalysts was studied. With heteropolyacids H4SiW12O40 and H3PW12O40 as catalyst the reaction afforded in high yield alkyl isobornyl ethers The mechanism of camphene hydration in water - alcohol mixtures catalyzed with acids was discussed.
- Radbil',Kulikov,Sokolova,Kartashov,Zolin,Radbil'
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p. 1618 - 1622
(2007/10/03)
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- Alkoxylation and hydration of camphene in the presence of acid catalysts
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The alkoxylation of camphene in the presence of various acid catalysts is studied. Alkylisobornyl ethers are obtained in high yields if the heteropolyacids H4SiW12O40 and H3PW12O40 are used
- Radbil',Kulikov,Sokolova,Kartashov,Zolin,Radbil'
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p. 524 - 528
(2007/10/03)
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- Reaction of alcohols with camphene over β-zeolite
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Alkylation of fatty-aromatic alcohols with camphene over β-zeolite takes two pathways: O-alkylation which is preceded by isomerization of protonated camphene and addition at the camphene double bond of a carbocation formed by protonation and subsequent dehydration of the alcohol. As a result, products of aralkylation or cyclization are obtained, depending on the alcohol structure.
- Fomenko,Korchagina,Yarovaya,Gatilov,Salakhutdinov,Ione,Barkhash
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p. 1006 - 1017
(2007/10/03)
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