Hydrochloric Acid → 1-Ethyl-4-piperidin-4-ylpiperazine

Participants

Reaction Steps

The protective group was removed by introducing 40 g (135 mmol) of tert-butyl 4-(4-ethylpiperazin-1-yl)piperidine-1-carboxylate from example a.1 into 200 ml of methanol and 1.8 l of dichloromethane and adding 100 ml of 5-6M HCl solution in isopropanol. A suspension resulted, and slight gas evolution was also observable. The reaction mixture was stirred at 40° C. (water bath temperature) for one hour and then stirred at room temperature for 48 hours. For complete deprotection, 50 ml of the 5-6M HCl solution in isopropanol were again added and the reaction mixture was stirred at 40° C. The dichloromethane was distilled out in a rotary evaporator. 200 ml of methanol and 30 ml of the 5-6M HCl solution in isopropanol were again added. The reaction mixture was stirred under reflux for one hour, during which a white suspension formed with strong evolution of gas. A mobile suspension then resulted and was cooled to room temperature. The precipitate was filtered off with suction and washed with methanol and diethyl ether. After drying, 36 g (117 mmol, 87%) of 1-ethyl-4-piperidin-4-ylpiperazine were isolated as chloride salt.

Provenance & Evidence