- 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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- Photostimulated reductive cyclization of o-nitrophenylazo dyes using sodium hydroxide in isopropyl alcohol. A new synthesis of 2-aryl-2H- benzotriazoles
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o-Nitrophenylazo dyes with NaOH were irradiated in isopropyl alcohol to give the corresponding benzotriazoles. The photostimulated reductive cyclization proceeds through the formation of N-oxides as an intermediate.
- Baik, Woonphil,Yoo, Chang Hyun,Koo, Sangho,Kim, Hern,Hwang, Yong Hyun,Kim, Byeong Hyo,Lee, Seok Woo
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p. 1779 - 1783
(2007/10/03)
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- Reductive cyclization of o-nitrophenylazobenzenes to 2-aryl-2H- benzotriazoles by SmI2
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In a mild reaction with SmI2, ortho-nitro substituted phenylazobenzenes have been converted into 2-aryl-2H-benzotriazoles.
- Kim, Byeong Hyo,Kim, Sun Kyong,Lee, Yoon Seok,Jun, Young Moo,Baik, Woonphil,Lee, Byung Min
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p. 8303 - 8306
(2007/10/03)
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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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- The Reaction of Some o-Nitroazobenzenes with Hydroxylamine
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The reaction of some representative o-nitroazobenzenes with hydroxylamine in ethanolic sodium hydroxide solution gave good to excellent yields of the corresponding 2-aryl-2H-benzotriazole 1-oxides.In some cases, the corresponding parent 2-aryl-2H-benzotriazoles were also obtained.Under the same reaction conditions, nitrobenzene was essentially unreactive.It Is suggested that the reactive species is diimide.
- Wilshire, John F.K.
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p. 617 - 622
(2007/10/02)
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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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- The Reduction of Some o-Nitrophenylazo Dyes with Thiourea S,S-Dioxide (Formamidinesulfinic Acid): a General Synthesis of 2-Aryl-2H-benzotriazoles and Their 1-Oxides
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Thiourea S,S-dioxide (formamidinesulfinic acid) reacts with o-nitrophenylazo dyes in ethanolic alkali to give, depending on the reaction conditions, either the corresponding 2-aryl-2H-benzotriazoles or their 1-oxides.The reagent is particularly effective for preparing in high yield 2-(2'H-benzotriazol-2'-yl)phenols, which are important ultraviolet absorbers.The corresponding reductions involving ammonium sulfide and sodium dithionite were also examined.The former reagent was unsatisfactory; the latter reagent behaved erratically and was a less effective reducing reagent than thiourea dioxide.Nevertheless, conditions were established whereby sodium dithionite furnished the 2-(2'H-benzotriazol-2'-yl)phenols in high yield and purity.
- Rosevear, Judi,Wilshire, John F. K.
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p. 2489 - 2497
(2007/10/02)
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- The Reduction of Some o-Nitrophenylazo Dyes with Glucose: A General Synthesis of 2-Aryl-2H-benzotriazole 1-Oxides
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The reduction of some representative o-nitrophenylazo dyes in ethanolic alkali with glucose gives the corrsponding 2-aryl-2H-benzotriazole 1-oxides in excellent yield.These 1-oxides are rapidly reduced to the parent benzotriazoles at room temperature by means of zinc dust/ethanolic alkali.This method provides a convenient preparation for 5-chlorobenzotriazoles, which are otherwise readily dechlorinated by zinc dust under more vigorous conditions
- Rosevear, Judi,Wilshire, John F. K.
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p. 2089 - 2093
(2007/10/02)
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