Hydrochloric Acid → 4-Amino-1-ethanesulfonylpiperidine

Triethylamine (10 mL) was added to a dichloromethane (90 mL) solution of Benzyl piperidin-4-ylcarbamate (5.09 g) at 0° C. followed by the dropwise addition of ethane sulfonylchloride (which may be referred to as sso10; 3.2 mL; TCI) and the resulting mixture was stirred overnight slowly raising to room temperature. 1 N Hydrochloric acid (90 mL; WAKO) was added to the reaction mixture solution, the resulting mixture was stirred for approx. 10 minutes, then the reaction mixture was extracted with chloroform, the organic layer was dried, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (Yamazen; chloroform/methanol). Palladium hydroxide (20% by weight, Wet-type, 5 g; NECHEM) was added to a methanol (90 mL) solution of this product under a nitrogen atmosphere. The atmosphere in a reaction vessel was replaced with hydrogen at room temperature, the resulting mixture was stirred overnight, the atmosphere in the reaction vessel was returned to a nitrogen atmosphere, the residue was removed by filtration, the solvent was evaporated under reduced pressure, and the residue was dried to give the title compound (3.32 g).