Synthesis method for generating 4-nitroimidazole by oxidizing 4-aminooimidazole

Abstract

The invention discloses a synthesis method for oxidizing 4-aminoimidazole to generate 4-nitroimidazole. The method is specifically carried out according to the following steps: step S1, oxidation: 4-aminoimidazole is added in the flask, then water and hydrogen persulfate are added and stirred for 12-24 hours at 30-60°C; step S2, Extraction: extract with dichloromethane after the reaction, and take the dichloromethane layer; step S3, distillation and desolventization: lower the temperature of the extract, and distill off the dichloromethane under reduced pressure to obtain 4-nitroimidazole. The present invention uses 4-aminoimidazole as a raw material to directly oxidize 4-nitroimidazole in one step, which simplifies the production process and reduces the cost of the process; and adopts hydrogen persulfate as the nitrating reagent instead of using concentrated sulfuric acid and sodium nitrite as the nitrating agent. The reagent has mild reaction conditions, and water is used as a solvent for the reaction, so the safety factor is high, and the yield of 4-nitroimidazole reaches 90%.

Description

technical field [0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a synthesis method for oxidizing 4-aminoimidazole to generate 4-nitroimidazole. Background technique [0002] 4-Nitroimidazole plays a huge role in the fields of pharmaceuticals, dyes, materials, etc. In addition, due to the high nitrogen content and good thermal stability of this compound, it shows great potential in the fields of propellants, explosives, and fireworks . The traditional method of synthesizing 4-nitroimidazole is through electrophilic nitration reaction or classic Sandmeyer reaction: [0003] [0004] Wherein the nitration reaction is to use concentrated nitric acid or a mixture of concentrated nitric acid and concentrated sulfuric acid as a nitrating reagent, but the safety of the reagents used in this method is relatively low, and may be subject to certain restrictions in large-scale industrial production, such as Chinese invention pat...

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Problems solved by technology

[0004] Wherein the nitration reaction is to use concentrated nitric acid or a mixture of concentrated nitric acid and concentrated sulfuric acid as a nitrating reagent, but the safety of the reagents used in this method is relatively low, and may be subject to certain restrictions in large-scale industrial production, such as Chinese invention patent (CN104892522A ) discloses a kind of synthetic method of 4-nitroimidazole, comprises the steps: step 1, in the stainless steel reactor of polytetrafluoroethylene liner, N 2 o 5 Dissolves in fuming nitric acid to form N 2 o 5 / fuming nitric acid saturated solution, followed by adding mesoporous SO 4 2- / ZrO 2- CeO 2 Superacid catalyst and imidazole are stirred and mixed at room temperature to form a slurry reaction solution, wherein the mol ratio of imidazole to fuming nitric acid is 1 / 2 to 1 / 5, and the catalyst consumption is 10 to 15% of the quality of fuming nitric acid; step 2, Seal the reaction kettle tightly, heat up to 25-50°C, and stir until the reaction is complete; step 3, cool and dilute the reaction solution in step 2 in ice water, let stand, separate layers, filter and recover the catalyst, and then extract and filter with dichloromethane The reaction solution, take the organic phase, rotary evaporation, drying to get 4-nitroimidazole, yield 72 ~ 90%, wherein the volume of ice water is 5 ~ 8 times the volume of fuming nitric acid; another example of Chinese invention patent (CN 104592123 A ) discloses a preparation method of 4-nitroimidazole, comprising the following steps: (1) adding imidazole to an aqueous sulfuric acid solution with a mass fraction of 98% and stirring continuously, and keeping the temperature for 18 to 25 minutes at 18 to 25° C. after the addition is complete , to obtain imidazolium disulfate solution; (2) heating the imidazolium disulfate solution obtained in step (1) to 45~55°C, adding N 2 o 5 - mix acid nitrating agent and stir to mix, N 2 o 5 -After adding the mixed acid nitrating agent dropwise, keep it warm for 30-35 minutes; (3) Cool the mixed system obtained in step (2) to 0-5°C, add the pre-cooled ice-water mixture and adjust the pH to 4.3-4.5 with ammonia water, and centrifuge Collect the precipitate, and vacuum-dry the precipitate to obtain 4-nitroimidazole; another example is that the Chinese invention patent (CN 103724275 A) discloses a preparation method for 4-nitroimidazole, which includes the following steps: preparing the reaction solution step: preparing the following Reaction solution I and reaction solution II, preparation of reaction solution I: mix imidazole and concentrated sulfuric acid at a mass ratio of 1:1-1:10 to prepare reaction solution I, preparation of reaction solution II: use concentrated nitric acid as reaction solution II, Or mix concentrated nitric acid and concentrated sulfuric acid according to the mass ratio of 1:19-9:1 to prepare reaction solution II; preparation of 4-nitroimidazole steps: use pump I with a flow rate of 1-200ml / min to add reaction solution I In the microreactor, use the pump II to add the reaction liquid II into the microreactor, the flow rate of the pump II is controlled according to the flow rate of the pump I, so that the concentrated nitric acid in the microreactor is 1.0-3.0 equivalent of imidazole, and heated to 50-150°C, after the reaction is complete, cool the reaction solution, and go through the separation and purification steps to obtain 4-nitroimidazole

The Sandmeyer reaction can be applied to a wider range of substrates, but the reaction will produce a very unstable diazonium salt intermediate under strongly acidic conditions

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