| AABI is short for5-acetoacetlamino benzimidazolone-2. It is an important kindof dye intermediates, mainly used in synthesis azo benzimidazolone-2pigments.Benzimidazolone-2pigments have a series of colors from orange to yellow whichsynthesized by5–acetoacetlamino benzimidazolone-2as intermediate. They aremainly used in the manufacture of high-grade automotive original paint, repairingpaint and metallic paint.This article is divided into two synthesis methods of5–acetoacetlaminobenzimidazolone-2. The first method includes four steps: firstly, I usedo-phenylendiamine and urea as raw materials in water to synthetizebenzimidazolone-2. The product is shallow purple crystal plate. The reactionconditions were optimized, the yield was96.01%, and the purity was99.90%by highperformance liquid chromatography (HPLC). The second step used concentratednitric acid in organic solvent chlorobenzene to synthetize5-nitro benzimidazolone-2.The product is green ball solid. The yield was98.60%and the purity was99.20%byHPLC. The third step used Raney Ni as catalyst and absolute ethanol as solvent tosynthetize ABI. This reaction belongs to liquid phase hydrogenation reductionreaction. The reaction conditions were optimized, the yield was94.14%and the puritywas99.90%by HPLC. Finally with double ketene as acylating reagent in watermedium, thus white solid AABI was obtained, the yield was92.17%and the puritywas99.70%by HPLC. The second method includes three steps: firstly, I usedo-phenylendiamine and urea as raw materials in the benzene solvent, then throughconcentrated nitric acid to get green ball solid5-nitro benzimidazolone-2, the yieldwas93.53%and the purity was99.30%by HPLC. Then, the second step usedamorphous Ni-B as catalyst, and absolute ethanol as the solvent to synthetize ABI.This reaction also belongs to liquid phase hydrogenation reduction reaction. The yieldwas93.78%and the purity was99.70%by HPLC. Finally with double ketene asacylating reagent in water medium, thus white solid AABI was obtained. The yieldwas92.17%and the purity was99.70%by HPLC. In this article the second method is the key method. Through changing theo-phenylendiamine, urea and nitric acid molar ratio respectively, the optimumreaction molar ratio was1:1.5:1.5. I prepared5kinds of amorphous alloy catalyst Ni-B with Ni(CH3COO)24H2O and KBH4by chemical reduction method. Usingamorphous Ni-B alloy catalysts for liquid phase catalytic hydrogenation reduction,the optimum reaction conditions were determined: with amorphous Ni-B catalyst tosynthesis of ABI, its dosage was5.5%-6.6%(relative to the quality of the5-nitrobenzimidazolone-2), reaction temperature was150℃, reaction pressure was2.0MPa,reaction time was8h, absolute ethanol was100ml. The yield of ABI was93.78%and the purity was over99%, catalyst recycling use was5times.Two methods were compared from three aspects: the raw material cost, catalystrecycling and the environmental impact respectively. Finally the second preparationof AABI was confirmed. |
