Hydrochloric Acid → gamma-(4-Benzyl-4-hydroxypiperidino)-2-chlorobutyrophenone hydrochloride

To a cooled solution of 3.6 g of γ-(4-benzyl-4-hydroxypiperidino)-2-aminobutyrophenone in 35 ml of 2N hydrochloric acid was added dropwise a solution of 0.74 g of sodium nitrite in 5 ml of water with stirring below 0° C. The resulting diazonium salt solution was added all at once to a cold suspension of 1.5 g of cuprous chloride in 5 ml of concentrated hydrochloric acid with vigorous stirring. The mixture was stirred for 30 minutes under cooling with ice, and stirring was continued for 2 hours at room temperature and then for 1 hour at 55°-60° C. After cooling, the reaction mixture was made alkaline, and extracted with chloroform. The extract was washed with water, dried and concentrated to a residue. The residue was treated with methanolic hydrogen chloride and recrystallization of the resulting solid matter from isopropanol gave γ-(4-benzyl-4-hydroxypiperidino)-2-chlorobutyrophenone hydrochloride.8c