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

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.

1. customThe protective group was removed
2. customA suspension resulted
3. stirringthe reaction mixture was stirred at 40° C
4. distillationThe dichloromethane was distilled out in a rotary evaporator
5. addition200 ml of methanol and 30 ml of the 5-6M HCl solution in isopropanol were again added
6. stirringThe reaction mixture was stirred
7. temperatureunder reflux for one hour, during which a white suspension
8. customformed with strong evolution of gas
9. customA mobile suspension then resulted
10. temperaturewas cooled to room temperature
11. filtrationThe precipitate was filtered off with suction
12. washwashed with methanol and diethyl ether
13. customAfter drying

ORD record

ord-441f974324bd4c8ba69302c8a37d4bc0

Source dataset

uspto-grants-2014_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08703774B2