Hydrochloric Acid → p-Toluenesulfonic acid

Participants

Reaction Conditions

Reaction Steps

80 ml of water and 60 g (0.592 mole) of 36% hydrochloric acid were placed in a 300-ml flask as a reactor, and cooled to 3° C. Thereto was dropwise added, at 2 to 5° C. with stirring, 96 g (0.112 mole) of an aqueous solution of a potassium salt of 2-amino-5-fluorothiophenol, followed by stirring for 1 hour. The system had a pH of 5.23. Thereto were added 20 g (0.105 mole) of p-toluenesulfonic acid monohydrate and 30 ml of tetrahydrofuran, followed by stirring for 30 minutes. Thereto was added 16.7 g (0.114 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 36.0 g of a p-toluenesulfonate of [2-(6-fluorobenzothiazolyl)]ethylamine (purity: 95.2%) (the yield was 82.8% relative to the potassium salt of 2-amino-5-fluorothiophenol).

Provenance & Evidence