Method for synthesizing isatoic anhydride

Abstract

The invention discloses a method for synthesizing isatoic anhydride, which comprises the following steps: (1) adding phthalimide to a reaction solvent; (2) controlling the temperature to be within the range of 40-45 DEG C, introducing chlorine gas, and reacting for 1.5-2 hours; (3) controlling the temperature to be below 45 DEG C, adding solid caustic soda, and then continuing to react for 0.5-1.5 hours; and (4) filtering and collecting salts to obtain an isatoic anhydride filtrate, cooling, crystallizing, filtering, and drying to obtain solid isatoic anhydride. The method for synthesizing the isatoic anhydride avoids the use of a large amount of virulent and dangerous chemical substances and has moderate anhydrous reaction conditions, and hydrogen chloride and sodium chloride as reaction byproducts can be treated to produce high-quality hydrochloric acid and industrial sodium chloride byproducts, thereby reducing the generation and the discharge of harmful impurities and a large amount of waste water difficult to treat. The yield can be up to 92% or above. Thus, the invention is suitable for industrial application.

Description

technical field [0001] The invention relates to a method for synthesizing isatoic anhydride, belonging to the field of fine chemicals. Background technique [0002] Isatoic anhydride, also known as Etoic anhydride, English name Isatoic anhydride, is a very useful chemical intermediate, which can react with both electrophilic reagents and nucleophilic reagents. It and its homologues and derivatives are widely used in the synthesis of agricultural chemicals, dyes, pigments, fragrances, flavors, medicines, ultraviolet absorbers, foaming agents, flame retardants, preservatives, bleaching agents, fungicides and sanitation Disinfectants and other fine chemical products. Its chemical structure is as follows: [0003] [0004] There are many existing synthesis methods of isatoic anhydride: [0005] (1) Use anthranilic acid as a raw material to react with phosgene or ethyl chloroformate, etc., and isatoic anhydride can also be obtained by reacting methyl anthranilate with phosg...

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Problems solved by technology

[0007] (3) Phthalic anhydride and azide react under the action of concentrated sulfuric acid, and the reaction process exotherms violently, and simultaneously generates a mixture of isatoic anhydride and benzimidazolone, which is also difficult to handle;

Although the yield of this method is high, it has high requirements on reaction temperature, time, and pH. If it deviates from the optimum conditions, the yield will be significantly reduced, and a large amount of waste water pollution that is difficult to handle will be generated in the reaction.

[0009] The traditional production process of synthesizing isatoic anhydride has many disadvantages in production, such as raw materials such as highly toxic and dangerous phosgene, chromium trioxide, etc., or problems such as relatively high reaction conditions or the production of a large amount of industrial wastewater and large pollution.

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