Thiophenol → 5-Phenylthio-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole

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Reaction Conditions

Reaction Steps

Into a two-liter three-necked flask equipped with stirrer, thermometer, distillation set-up and nitrogen supply are charged 268.4 g (0.75 mole) of 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole, 93.7 g (0.825 mole) of thiophenol and 400 mL of N,N-dimethylformamide (DMF). The reactor is evacuated and filled with nitrogen three times to establish an inert atmosphere. To the slurry is added 66.0 g (0.825 mole) of 50% aqueous sodium hydroxide solution and the mixture heated to reflux. At this point water distills off as an azeotrope until the head-temperature reaches 132° C. and a reaction temperature of 150° C. After 18 hours there is no residual starting benzotriazole compound observed (TLC). At reduced pressure most of the DMF is distilled off at 80° C. To the residue is then charged 500 mL of toluene and 200 mL of water. After slow stirring for a few minutes at 80° C. the lower aqueous phase is drained off. The addition of 200 mL of water is repeated twice more, the second time with addition of 1 mL of acetic acid. Any residual water is azeotroped off until a clear solution is obtained. Approximately 300 mL of toluene is removed under partial vacuum at 90° C. and to the concentrate is added 800 mL of isopropanol, resulting in rapid crystallization. The reaction mixture is cooled to 20° C. and filtered. The light yellow crystals are washed with 250 ml of isopropanol and dried to give 317 g (97.9% of theory) of the title compound, mp. 132°-134° C.

Provenance & Evidence