Bisoctrizole synthesis

10333-53-6

3147-75-9

103597-45-1

1. Synthesis procedure: In a 500 mL three-necked flask equipped with a stirrer, thermometer and distillation receiver, 323 g of ultraviolet absorber UV-329, 4 g of powdered sodium hydroxide, 128 g of bis(di-n-propylamino)methane and 15 g of tetrabutylammonium bromide were added sequentially. The reaction mixture was heated to 130°C under reduced pressure at 100 mmHg with continuous stirring. During the reaction, the resulting di-n-propylamine was collected by distillation. After the reaction was carried out for 2 h, the heating was stopped and the vacuum was released. A total of 108 g of di-n-propylamine was recovered (theoretical yield: 122 g) with 88.5% recovery and 98.6% purity. 2. Purification step: When the temperature of the reaction system was lowered to 110°C, 500 g of toluene was slowly added to dissolve all the solids. After complete dissolution, the temperature of the system was lowered to 90°C. About 40 g of 18% aqueous hydrochloric acid was added dropwise slowly and stirred until the reaction system was neutral. The reaction mixture was transferred to a beaker and the crystals were cooled and crystallized in an ice water bath for 4-5 hours. The crystals were collected by filtration and washed twice with 150 mL of deionized water and twice with 250 mL of methanol sequentially. The resulting wet product was dried at 100~110°C to obtain 266 g of ultraviolet absorber UV-360 (theoretical yield: 329 g), the product melting point was 197~198°C, the yield was 80.9% and the purity was 99.6%.