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

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

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 2020 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.

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