- The Continuous Synthesis of 2-(2'-Hydroxy-5'-Methylphenyl)Benzotriazole over Cu/γ-Al2O3
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Abstract: The samples of 20% Cu/γ-Al2O3, 20% Co/γ-Al2O3 and 20% Ni/γ-Al2O3 were prepared as hydrogenation catalysts for continuous synthesis of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. The best yield (86.62%) was afforded by the 20% Cu/γ-Al2O3 catalyst. The characterizations results obtained for the 20% Cu/γ-Al2O3 sample confirmed that Cu particles are evenly distributed over the surface of γ-Al2O3. A reduction of acid sites in the catalyst favored the selectivity to 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. Furthermore, the effect of Cu content, reaction temperature, hydrogen pressure and liquid hourly space velocity was studied. Finally, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole in 86.62% yield was attained under the optimized conditions.
- Yan,Si,Tao,Liu,Wang,Li
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p. 635 - 641
(2019/10/19)
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- Catalytic hydrogenation of 2-nitro-2′-hydroxy-5′-methylazobenzene over solid base-hydrogenation bifunctional catalysts: Effect of alkali metals on Pd/γ-Al2O3
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Alkali metals doped Pd solid base-hydrogenation bifunctional catalysts were prepared, characterized, and employed in the hydrogenation of 2-nitro-2′-hydroxy-5′-methylazobenzene. The results indicated that the basicity of catalyst endowed by the alkali met
- Si, Leilei,Wang, Bowei,Chen, Shipeng,Hou, Jingru,Yan, Xilong,Li, Yang,Chen, Ligong
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- Reductive cyclization of 2-nitro-2′-hydroxy-5′-methylazobenzene to benzotriazole over K-doped Pd/γ-Al2O3
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A series of Pd/γ-Al2O3 catalysts modified by potassium salts were prepared and evaluated in the reductive cyclization of 2-nitro-2′-hydroxy-5′-methylazobenzene without additional base. These solid base-hydrogenation bifunctional catalysts were characterized and the results demonstrated that potassium salts could have an important impact on the properties and catalytic performance of Pd/γ-Al2O3.
- Wang, Bowei,Si, Leilei,Yuan, Yanyan,Li, Yang,Chen, Ligong,Yan, Xilong
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p. 16766 - 16771
(2016/02/20)
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- One-pot synthesis of benzotriazoles and benzotriazole 1-oxides by reductive cyclization of o-nitrophenylazo compounds with benzyl alcohol
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Reductive cyclization of 2-[(2-nitrophenyl)azophenols 1 with benzyl alcohol and sodium hydroxide afforded 2-(2H-benzotriazol- 2-yl)phenols 3 and their 1-oxide 2 in good to excellent yields.
- Farkas, Renata,Toerincsi, Mercedes,Kolonits, Pal,Alonso, Oscar Jimenez,Novak, Lajos
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experimental part
p. 2579 - 2588
(2010/04/27)
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- Liquid-phase hydrogenation of 2-nitro-2′-hydroxy-5′- methylazobenzene on raney nickel at low temperatures
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The character of changes in the concentrations of intermediate products at the initial stage of the hydrogenation of 2-nitro-2′-hydroxy-5′- methylazobenzene (I) on Raney nickel at 275 K and the reasons for their dependence on the composition of the solvent were determined. The smallest amount of I and the largest yield of substituted benzotriazole N-oxide were obtained when the reaction was conducted in a 2-propanol-water solvent containing sodium hydroxide. Conversely, the addition of acids to the solvent sharply increased the yield of the nitrohydrazo derivative. The selectivity of hydrogenation with respect to the substituted benzotriazole was determined by the ratio between the rates of hydrogenation of the nitro and azo groups in the initial compound and intramolecular homogeneous rearrangements of intermediate products.
- Zuenko,Nemtseva,Lefedova,Nikolaev
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p. 877 - 881
(2007/10/03)
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- Hydrogenation kinetics of 2′-hydroxy-5′ -methyl-2-nitroazobenzene under quasisteady conditions
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The kinetics of the liquid-phase hydrogenation of 2′-hydroxy-5′ -methyl-2-nitroazobenzene on skeletal nickel in propan-2-ol and its mixtures with water and sodium hydroxide was studied under quasisteady conditions ensured by a measured substrate feed into a reaction vessel. 2-(2-Hydroxy-5-methylphenyl)benzotriazole N-oxide, 2′-hydroxy-5′ -methyl-2-nitrohydrazobenzene, and aromatic amines were found to be the major reaction intermediates under both steady and quasi-steady conditions, provided the compositions of the solvents are the same. The highest reaction selectivity for the target product, namely, 2-(2-hydroxy-5-methylphenyl)benzotriazole, can be reached at low concentrations of the starting reagent in a chemisorbed layer and high rates of cyclization of 2′-hydroxy-5′ -methyl-2-nitrohydrazobenzene into 2-(2-hydroxy-5-methylphenyl)benzotriazole N-oxide.
- Lefedova
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p. 1266 - 1269
(2007/10/03)
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- The effect of the amount of raney nickel and hydrogen pressure on the rate and selectivity of liquid-phase hydrogenation of 2-nitro-2′-hydroxy-5′-methylazobenzene
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An increase in the content of Raney nickel and hydrogen pressure accelerated the hydrogenation of 2-nitro-2′-hydroxy-5′-methylazobenzene and increased the yield of substituted benzotriazole because of a more complete conversion of intermediate substituted benzotriazole N-oxide. The total selectivity with respect to compounds containing the benzotriazole ring increased when sodium hydroxide was introduced into the aqueous-alcoholic solvent and the amount of the catalyst was decreased. Changes in the selectivity of the reaction were caused by changes in the ratio between the rates of homogeneous benzotriazole cyclization and heterogeneous stages of the complex multistage process of 2-nitro-2′-hydroxy-5′-methylazobenzene hydrogenation.
- Nemtseva,Lefedova,Gostikin,Zuenko
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p. 917 - 921
(2007/10/03)
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- Electrochemical synthesis of 2-aryl-2H-benzotriazoles and their N-oxides by controlled potential cathodic electrolysis
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Using a divided cell, reductive cyclizations of o-nitrophenylazo dyes (1) toward 2-aryl-2H-benzotriazole-1-oxides (2) or 2-aryl-2H-benzotriazoles (3) were successfully accomplished by the controlled potential cathodic electrolysis reactions. 1 was transformed to 2 under neutral conditions while 1 was transformed to 3 under basic conditions.
- Kim, Byeong Hyo,Lee, Doo Byung,Kim, Dae Ho,Han, Rongbi,Jun, Young Moo,Baik, Woonphil
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p. 841 - 850
(2007/10/03)
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- Fluorenol catalyzed reduction of o-nitroazobenzenes and 2-aryl-2H-benzotriazole-N-oxides
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A process for producing 2-aryl-2H-benzotriazole by reducing an o-nitroazobenzene with a saccharide having an aldehyde group as a reducing agent in the presence of fluorenol as a catalyst and a base in solution. The reaction is conducted at a temperature of from about 60° C. to about 80° C. The reaction time and amount of catalyst is significantly reduced compared to the use of an aromatic ketone catalyst. The invention also provides a method for producing 2-aryl-2H-benzotriazole by reducing a 2-aryl-2H-benzotriazole-N-oxide intermediate with a saccharide having an aldehyde group as a reducing agent, in the presence of fluorenol under similar conditions.
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- Method for preparing 2-phenylbenzotriazoles
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This invention relates to a method for preparing a 2-phenylbenzotriazole of formula I, STR1 (wherein R1 represents hydrogen or chlorine atom, a lower alkyl group having a carbon number of 1 to 4, a lower alkoxy group having a carbon number of 1 to 4, carboxyl group, or sulfonic acid group; R2 represents hydrogen or chlorine atom, a lower alkyl group having a carbon number of 1 to 4, or a lower alkoxy group having a carbon number of 1 to 4; R3 represents hydrogen or chlorine atom, an alkyl group having a carbon number of 1 to 12, a lower alkoxyl group having a carbon number of 1 to 4, phenyl group, a phenyl group substituted with an alkyl group having a carbon number of 1 to 8, phenoxy group, or a phenylalkyl group, the alkyl part of which has a carbon number of 1 to 4; R4 represents hydrogen or chlorine atom, hydroxyl group, or a lower alkoxy group having a carbon number of 1 to 4; and R5 represents hydrogen atom, an alkyl group having a carbon number of 1 to 12, or a phenylalkyl group, the alkyl part of which has a carbon number of 1 to 4), which comprises reducing an o-nitroazobenzene of formula III, STR2 (wherein R1, R2, R3, R4 and R5 are as defined above) with at least one selected from the group consisting of primary and secondary alcohol reducing agents in the presence of an aromatic ketone catalyst and base. This invention further relates to a method for preparing a 2-phenylbenzotriazole of formula I as defined above, which comprises reducing 1 mole 2-phenylbenzotriazole-N-oxide of formula II, STR3 (wherein R1, R2, R3, R4 and R5 are as defined above) with 0.4 to 0.7 mole primary alcohol and/or 0.8 to 1.4 mole secondary alcohol in the presence of an aromatic ketone catalyst and base. This invention still further relates to a method for preparing a 2-phenylbenzotriazole-N-oxide of formula II as defined above, which comprises reducing 1 mole o-nitroazobenzene of formula III as defined above with 0.4 to 0.7 mole primary alcohol and/or 0.8 to 1.4 mole secondary alcohol in the presence of an aromatic ketone catalyst and base.
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- Method for preparing 2-phenylbenzotriazoles and 2-phenylbenzotriazole-N-oxides
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This invention relates to a method for preparing 2-phenylbenzotriazoles having the formula I, STR1
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- Method for preparing 2-phenylbenzotriazoles and 2-phenylbenzotriazole-N-oxides
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A method for preparing a 2-phenylbenzotriazole of formula I wherein R1 is H, Cl, C1-4alkyl, C1-4alkoxy, COOH or SO3H; R2 is H, Cl, C1-4alkyl or C1-4alkoxy; R3 is H, Cl, C1-12alkyl, C1-4alkoxy, phenyl, (C1-8alkyl)phenyl, phenoxy or phenyl(C1-4alkyl); R4 is H, Cl, OH or C1-4alkoxy; and R5 is H, C1-12alkyl or phenyl(C1-4alkyl), comprises reducing a nitroazobenzene of formula III = wherein R1, R2, R3, R4 and R5 are as defined above, with a saccharide in the presence of a hydrogen transfer catalyst and base. This method can be conducted in one or two steps. The individual steps, the first from the nitroazobenzene to a 2-phenylbenzotriazole-N-oxide of formula II and the second (II→I) are independent aspects of the invention.
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- Method for preparing 2-phenylbenzotriazoles and 2-phenylbenzotriazole-N-oxides
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This invention relates to a method for preparing a 2-phenylbenzotriazole of formula I, STR1 (wherein R1 represents hydrogen or chlorine atom, a lower alkyl group having a carbon number of 1 to 4, a lower alkoxyl group having a carbon number of 1 to 4, carboxyl group, or sulfonic acid group; R2 represents hydrogen or chlorine atom, a lower alkyl group having a carbon number of 1 to 4, or a lower alkoxyl group having a carbon number of 1 to 4; R3 represents hydrogen or chlorine atom, an alkyl group having a carbon number of 1 to 12, a lower alkoxyl group having a carbon number of 1 to 4, phenyl group, a phenyl group substituted with an alkyl group having a carbon number of 1 to 8, phenoxy group, or a phenylalkyl group, the alkyl part of which has a carbon number of 1 to 4; R4 represents hydrogen or chlorine atom, hydroxyl group, or a lower alkoxyl group having a carbon number of 1 to 4; and R5 represents hydrogen atom, an alkyl group having a carbon number of 1 to 12, or a phenylalkyl group, the alkyl part of which has a carbon number of 1 to 4), which comprises reducing an o-nitroazobenzene of formula III, STR2 (wherein R1, R2, R3, R4 and R5 are as defined above) with an aldehyde reducing agent in the presence of an aromatic ketone catalyst and base. This invention further relates to a method for preparing a 2-phenylbenzotriazole of formula I as derfined above, which comprises reducing 1 mole 2-phenylbenzotriazole-N-oxide of formula II, STR3 (wherein R1, R2, R3, R4 and R5 are as defined above) with 1 to 4 mole aldehyde in the presence of an aromatic ketone catalyst and base. This invention still further relates to a method for preparing a 2-phenylbenzotriazole-N-oxide of formula II as defined above, which comprises reducing 1 mole o-nitroazobenzene of formula III as defined above with 1 to 2 mole aldehyde in the presence of an aromatic ketone catalyst and base.
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- Method for preparing 2-phenylbenzotriazoles and 2-phenylbenzotriazole-N-oxides
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A method for preparing a 2-phenylbenzotriazole of formula I wherein R1 is H, Cl, C1-4alkyl, C1-4alkoxy, COOH or SO3H; R2 is H, Cl, C1-4alkyl or C1-4alkoxy; R3 is H, Cl, C1-12alkyl, C1-4alkoxy, phenyl, (C1-8alkyl)phenyl, phenoxy or phenyl(C1-4alkyl); R4 is H, Cl, OH or C1-4alkoxy; and R5 is H, C1-12alkyl or phenyl(C1-4alkyl), comprises reducing a nitroazobenzene of formula III wherein R1, R2, R3, R4 and R5 are as defined above, with an aldehyde, in the presence of an aromatic ketone and base. This method can be conducted in one or two steps. The individual steps, the first from the nitroazobenzene to a 2-phenylbenzotriazole-N-oxide of formula II and the second (II→I) are independent aspects of the invention.
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- Method of making hydroxyarylbenzotriazoles and their N-oxides
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Catalytic hydrogenation of o-nitrophenylazohydroxyaryls in an alkaline medium yields hydroxyarylbenzotriazoles; under mild conditions an N-oxide is formed. E.g., 6-tert-butyl-2-(5'-chloro-2'-nitrohenylazo)-p-cresol is hydrogenated to 5-chloro-2-(3'-tert-b
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