- Continuous preparation method of 2-nitro-2'-hydroxy-5'-methyl azobenzene
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The invention discloses a preparation method of 2-nitro-2'-hydroxy-5'-methyl azobenzene. According to the continuous preparation method, o-nitroaniline/sodium nitrite/acid/p-cresol is taken as a raw material, a micro-channel reactor is connected in series with a rotary liquid membrane reactor, and the reaction temperature, the reaction time and the like are accurately controlled, so that an azo intermediate 2-nitro-2'-hydroxy-5'-methyl azobenzene is prepared with high conversion rate and high selectivity. The method has the advantages of being simple in process, high in production efficiency, safe, environmentally friendly and easy to industrialize.
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Paragraph 0018-0022
(2021/06/21)
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- Simultaneous displacement of a nitro group during coupling of diazotized o-nitroaniline with phenols
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During the diazo-coupling reaction, nucleophilic displacement of a nitro group was also observed. This was the main reaction (1→7) when the starting amine bore either a chlorine or methoxy group at the para position (1b-c). The newly prepared compounds (7) might serve as convenient building blocks in synthesis of some heterocycles. Versita Warsaw and Springer-Verlag Wien 2010.
- Farkas, Renata,Toerincsi, Mercedesz,Kolonits, Pal,Fekete, Jenoe,Alonso, Oscar Jimenez,Novak, Lajos
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experimental part
p. 300 - 307
(2011/10/18)
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- Synthesis of new ultraviolet light absorbers based on 2-aryl-2H- benzotriazoles
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A procedure for the synthesis of some new ultraviolet absorbers of the benzotriazole series is reported. The compounds bear a carboxylic or a formyl group para to the hydroxy group, and these functionalities impart to the absorbers improved compatibility with certain disperse dyes on polyester fibers.
- Koutsimpelis, Aristides G.,Screttas, Constantinos G.,Igglessi-Markopoulou, Olga
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p. 1393 - 1401
(2007/10/03)
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- Processes for the preparation of benzotriazole UV absorbers
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Provided is a process for preparing 2H-benzotriazole UV absorbers containing a perfluoroalkyl moiety at the 5-position of the benzo ring, for example a trifluoromethyl group, which involves diazotizing the perfluoroalkyl substituted o-nitroaniline using concentrated sulfuric acid plus sodium nitrite or nitrosylsulfuric acid to form the corresponding monoazobenzene intermediate via the diazonium salt intermediate which is reduced to the corresponding 5-perfluoroalkyl substituted 2H-benzotriazole UV absorber compound by conventional reduction means. Also provided is a novel one-pot, multiphase reaction for the preparation of 2(2-nitrophenylazo) substituted phenols, which are precursors for 2H-benzotriazole UV absorbers.
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- Processes for the preparation of benzotriazole UV absorbers
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Provided is a process for preparing 2H-benzotriazole UV absorbers containing a perfluoroalkyl moiety at the 5-position of the benzo ring, for example a trifluoromethyl group, which involves diazotizing the perfluoroalkyl substituted o-nitroaniline using concentrated sulfuric acid plus sodium nitrite or nitrosylsulfuric acid to form the corresponding monoazobenzene intermediate via the diazonium salt intermediate which is reduced to the corresponding 5-perfluoroalkyl substituted 2H-benzotriazole UV absorber compound by conventional reduction means. Also provided is a novel one-pot, multiphase reaction for the preparation of 2(2-nitrophenylazo) substituted phenols, which are precursors for 2H-benzotriazole UV absorbers.
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- High caustic coupling process for preparing substituted 2-nitro-2'-hydroxyazobenzenes
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Substituted 2-nitro-2'-hydroxyazobenzenes are prepared by adding an aqueous mineral acid solution of a diazotized o-nitroaniline to a strongly alkaline lower alkanol or aqueous lower alkanol solution of a substituted phenol, containing sufficient alkali metal hydroxide to assure a pH value substantially over 11 and an excess of hydroxyl ion in the reaction mixture even after all the acidic diazonium salt solution is added, wherein the reaction solvent mixture is at least 50% by weight of lower alkanol, at a reaction temperature between -15° C. and +30° C. The o-nitroazobenzenes obtained are intermediate products useful in the manufacture of benzotriazole UV absorbers.
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