Study On The Improvement Of The Synthesis Process Of Aminobenzimidazolone Derivatives

Aminobenzimidazolone derivatives are the main intermediate of the high gradeazo pigments, which can be used in synthesizing kinds of Pigment. These kinds ofpigments have plenty of excellent properties, are widely applied in the plastics, inkand paint industry. Currently, there are some serious disadvantages in the synthesis of5-amino-1,3-dihydro-2H-benzimidazol-2-one(BI) and5-amino-6-methyl-1,3-dihydro-2H-benzimidazol-2-one(AMBI). Therefore, it is significance to study on thesynthesis process of BI and AMBI, and then applied to the industrial production.In this thesis, we studied on the synthesis process of BI and AMBI. BI wasprepared from5-nitro-1,3-dihydro-2H-benzimidazol-2-one, using iron power, sodiumsulphide,80%hydrazine hydrate as reducing agent, respectively. Finally hydrazinehydrate was selected as reducing agent. After the determination of80%hydrazinehydrate as reductant, single-factor was used to study the relationship of the yield of BI,and the experimental factors including solvents, addition methods, dropping time andamount of hydrazine hydrate, kinds of catalyst. Then the preferred process conditionwere obtained: using ethanol as the solvent and10%FeO(OH)/C as the catalyst,4.48g5-nitro-1,3-dihydro-2H-benzimidazol-2-one,50mL ethanol,4equivalent of80%hydrazine hydrate, dropping time of2hours,5%catalyst (by weight of5-nitro-1,3-dihydro-2H-benzimidazol-2-one), the yield of BI can reach90.2%. What’s more,Box-Behnken Design of response surface methodology was used to explore theoptimal condition of the three key factors:4equivalent of80%hydrazine hydrate,dropping time of3hours,5.2%catalyst, the yield of BI can reach92.2%.In this thesis, we used3,4-diaminotoluene as starting material,5-nitro-6-methyl-1,3-dihydro-2H-benzimidazol-2-one was synthesized by the condensation and thenitration reaction. Based on the study of BI, AMBI was synthesized with80%hydrazine hydrate as reductant, and the results show that the optimum catalyst isFeCl3supported on activated carbon with high surface area. Then the uniformdesign(U8＊(84)) was used to explore the optimal condition:4.83g5-nitro-6-methyl-1,3-dihydro-2H-benzimidazol-2-one,60mL ethanol,6.9mL of80%hydrazinehydrate, dropping time of0.5hours,15%catalyst, reflux reaction of3hours, the yield of AMBI can reach79.6%with a purity of97.2%. The chemical structure of the targetproduct is confirmed by1H-NMR.