Hydrochloric Acid → p-Toluenesulfonic acid

Participants

Reaction Conditions

Reaction Steps

48.2 g (0.056 mole) of an aqueous solution of a potassium salt of 2-amino-5-fluorothiophenol was placed in a 300-ml flask as a reactor, and cooled to 1° C. Thereto was dropwise added 72.0 g (0.296 mole) of 15% hydrochloric acid at 0 to 5° C. with stirring, followed by stirring for 1 hour. The system had a PH of 5.40. Thereto were added 9.7 g (0.051 mole) of p-toluenesulfonic acid monohydrate and 15 ml of tetrahydrofuran, followed by stirring for 30 minutes. Thereto was added 8.1 g (0.055 mole) of D-alanine-N-carboxyanhydride (purity: 78.3%) at 0° C. The resulting mixture was aged at 15 to 20° C. for 18 hours. The resulting crystals were collected by filtration and dried at 60° C. to obtain 12.2 g of a p-toluenesulfonate of [2-(6-fluorobenzothiazolyl)]ethylamine (purity: 76.5%) (the yield was 45.2% relative to the potassium salt of 2-amino-5-fluorothiophenol).

Provenance & Evidence