70693-50-4Relevant articles and documents
Preparing method of ultraviolet absorber UV-234
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, (2019/08/26)
The invention provides a preparing method of an ultraviolet absorber UV-234. The preparing method comprises the steps of conducting ammoniation, diazotization, coupling, first-step reduction, second-step reduction reaction and post-treatment on ortho-nitrochlorobenzene to prepare 2-[2'-hydroxy-3',5'-di(alpha,alpha-dimethyl benzyl)phenyl]benzotriazole. According to the preparing method, ortho-nitrochlorobenzene is ammonified by adopting ammonium hydroxide with the concentration of 10-25%, then is subjected to diazotization with nitrite to produce diazonium salt, no diazotization needs to occurunder a strong acid medium, by-product ammonium hydroxide of existing products of a company is comprehensively utilized, low emission of three wastes is achieved, and the required cost is low; a two-step reduction method is adopted in a reduction ring closing process of intermediate azo products, the situation is avoided that a strong reduction agent directly reduces azo double bonds into amine, impurity production is reduced, and not only is the purity of the products increased but also the product yield is increased.
Processes for the preparation of benzotriazole UV absorbers
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, (2008/06/13)
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.
High caustic coupling process for preparing substituted 2-nitro-2'-hydroxyazobenzenes
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, (2008/06/13)
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.
