- Sulfated zirconia: An efficient catalyst for the Friedel-Crafts monoalkylation of resorcinol with methyl tertiary butyl ether to 4-tertiary butylresorcinol
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Friedel-Crafts alkylation of resorcinol with methyl tertiary butyl ether was carried out over sulfated zirconia (SZ) catalysts in the liquid phase. The SZ catalysts were synthesized by an impregnation method with different sulfur amounts and characterized by XRD, FT-IR, nitrogen sorption, XPS, SEM, pyridine-FTIR, and NH3-TPD. The effect of the sulfur loading on the total acidity and catalytic activity was investigated. The influence of the nature of the solvents on the alkylation reaction was inspected in terms of their acceptor and donor numbers. The sulfur loading, amount of solvent, temperature, catalyst amount, mole ratio and reusability of the catalyst were examined. The SZ catalyst synthesized by impregnating 1 N sulfuric acid was found to be highly selective for the monoalkylation to 4-tertiary butyl resorcinol (72%) with a resorcinol conversion of ~70%. The catalyst was recycled thrice with a negligible decrease in the yield for 4-tertiary butylresorcinol. The SZ exhibited the best performance at low temperature (60 °C) among the different types of solid acid catalysts studied so far.
- Marakatti, Vijaykumar S.,Marappa, Shivanna,Gaigneaux, Eric M.
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- Temporary inactivation of plasma amine oxidase by alkylhydrazines. A combined enzyme/model study implicates cofactor reduction/reoxidation but cofactor deoxygenation and subsequent reoxygenation in the case of hydrazine itself
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It has been known for some time that hydrazine and its methyl and 1,1-dimethyl analogues induce inactivation of the copper-containing quinone-dependent plasma amine oxidase but that the activity recovers over time, suggesting metabolism of all three inhib
- Lee,Jeon,Huang,Sayre
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- Synergistic role of Lewis and Br?nsted acidities in Friedel-Crafts alkylation of resorcinol over gallium-zeolite beta
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The role of Lewis and Br?nsted acidities in alkylation of resorcinol is demonstrated through the gallium-zeolite beta by varying the amount of Lewis and Br?nsted acid sites. The synergism of Lewis and Br?nsted acid sites takes place heterogeneously in Friedel-Crafts alkylation of resorcinol with methyl tert-butyl ether to produce 4-tert-butyl resorcinol and 4,6-di-tert-butyl resorcinol as the major and minor products, respectively.
- Nur, Hadi,Ramli, Zainab,Efendi, Jon,Rahman, Aiman Najati Akmar,Chandren, Sheela,Yuan, Lai Sin
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- Alkylation of resorcinol with tertiary butanol over zeolite catalysts: Shape selectivity vs acidity
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The catalytic performance of various zeolites such as H-ZSM-5, H-Y, H-beta, H-Mordenite in resorcinol alkylation with tertiary butanol demonstrated that pore characteristics have major influence on product selectivity, whereas acid strength and number of acid sites influenced resorcinol conversion. The passivation of external surface of H-beta zeolite by silylation and amine poisoning produced shape selectively O-alkylated resorcinol methyl tert butyl ether (RMTBE) and 4-tert butyl resorcinol (4-TBR). We propose that 4-TBR formation goes over external acid sites through RMTBE isomerization, whereas formation of 4-TBR takes place inside the pores through direct C-alkylation mechanism.
- Marakatti, Vijaykumar S.,Gaigneaux, Eric M.
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- Role of Lewis and Br?nsted acid sites in resorcinol: Tert-butylation over heteropolyacid-based catalysts
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The role of Br?nsted and Lewis acid sites at the surface of heteropolyacid-based catalysts was studied in resorcinol alkylation with methyl-Tert-butylether. Three sets of catalysts, SiO2/HPW, TiO2/HPW and ZrO2/HPW (where HPW stands for phosphotungstic acid hydrate), synthesized by the hydrolytic sol-gel method were investigated. The surface total acidity was characterized by ammonia chemisorption and thermo-programmed desorption. In addition, infrared analysis of adsorbed pyridine was performed to distinguish between Br?nsted and Lewis sites. The resorcinol conversion was correlated to the fraction of Br?nsted sites present at the catalyst surface based on the total acidity. The results pointed out the importance of considering both Br?nsted and Lewis sites as active players in the mechanism of resorcinol alkylation: Lewis sites have the role of adsorbing the substrate close to the tert-butyl cation, which is formed on Br?nsted sites. Resorcinol conversion can be increased to a maximum if the right Br?nsted/Lewis ratio is attained at the catalyst surface.
- Gaigneaux, Eric M.,Marakatti, Vijaykumar S.,Pezzotta, Chiara
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p. 7984 - 7997
(2020/12/28)
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- Candida antarctica lipase B-catalyzed regioselective deacylation of dihydroxybenzenes acylated at both phenolic hydroxy groups
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Candida antarctica lipase B proved to be highly active in the deacylation of substituted hydroquinones and resorcinols acylated at both phenolic hydroxy groups. The deacylation reactions were much faster than the corresponding direct acylations of these dihydroxybenzenes catalyzed by the same lipase. More importantly, they took place generally in a markedly regioselective manner: the acyloxy group remote from the substituent was preferentially cleaved. The main or exclusive products obtained were the regioisomers of those produced through the direct acylation of the dihydroxybenzenes. In the case of alkyl-substituted hydroquinone derivatives, the regioselectivity increased with an increase in the bulk of the substituent. In the case of 4-substituted diacylated resorcinols, the 3-O-monoacyl derivatives were obtained generally as the sole products. Quite interestingly, some secondary alcohols proved to act as better acyl acceptors than the corresponding primary alcohols in these enzymatic deacylations.
- Miyazawa, Toshifumi,Hamada, Manabu,Morimoto, Ryohei
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- Model studies of topaquinone-dependent amine oxidases. 1. Oxidation of benzylamine by topaquinone analogs
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The aerobic oxidation of benzylamine by model compounds of topaquinone, the active site organic cofactor in copper-containing amine oxidases, was studied in order to elucidate the chemical function of the cofactor in substrate oxidation. In this study, topaquinone hydantoin (1(ox)) and a series of 2-hydroxy-5-alkyl-1,4-benzoquinones which differ in the bulk of their alkyl substituent (5, 6, 7, and 8) were employed as model compounds of the cofactor. The p-quinones (9, 10, 11, and 12) and the o-quinone (13 and 14) were prepared in order to compare them to the topaquinone analogs. Benzylamine was oxidized by the topaquinone analogs (1(ox), 5, 6, 7, and 8) to yield N-benzylidenebenzylamine (PhCH = NCH2Ph) as a sole product in acetonitrile at room temperature. The quinones bearing a bulky substituent (1(ox), 5, and 6) were found to be more efficient catalysts than those bearing a small primary alkyl group (7 and 8). In the latter case, the dimers (16 and 17) of the substrate Schiff base intermediates (15, R = methyl, ethyl) were isolated. The p-quinones (9, 10, 11, and 12) were catalytically inactive. The o-quinones (13 and 14) had detectable catalytic activity at room temperature. In anaerobic reactions of the o-quinones (13 and 14) with benzylamine, quantitative formation of the product (PhCH = NCH2Ph) was observed. For both o-quinones, products and intermediates which support a transamination mechanism were identified by 1H NMR spectroscopy. The order of reactivity of quinones (5 > 14 > 13) reflects their redox potentials, such that regeneration of quinone may be rate-determining with o-quinones. These results demonstrate a substantial role of the 2-hydroxyl group of the topaquinone in preventing the formation of Michael adducts with substrate amine and in facilitating the reoxidation of aminoresorcinol intermediates.
- Mure, Minae,Klinman, Judith P.
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p. 8698 - 8706
(2007/10/02)
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- ALKYLATION OF RESORCINOL BY TERTIARY ALCOHOLS
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The initial product from the alkylation of resorcinol by tert-butyl alcohol in the presence of phosphoric or sulfuric acids is 4-tert-butylresorcinol, which is then converted into 4,6-disubstituted resorcinol.The optimum yields of 4,6-di-tert-alkylresorcinols are obtained with sulfuric acid as catalyst with the resorcinol, tertiary alcohol, and acid in molar ratios of 1:3:0.5.
- Korneev, S. M.,Nikolaev, V. A.
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p. 1493 - 1495
(2007/10/02)
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