反应详情

Crude (S)(−)-2-piperidinecarboxylic acid (19.5 g, prepared as described in example 26) was suspended in ethanol (250 ml), and thionyl chloride (40 ml, 0.46 mol) was added dropwise. After addition was complete, the suspension was heated at reflux temperature for 2 h. The mixture was filtered hot, and the filtrate was cooled to room temperature. Filtration and evaporation in vacuo afforded an oil, which was crystallised by rubbing. Ethanol (10 ml) was added, followed by slow addition of diethyl ether (150 ml). The precipitated solid was filtered off, washed with diethyl ether and dried by suction to give 13.8 g (35% calculated from 2-piperidinecarboxylic acid) (S)-(−)-2-piperidinecarboxylic acid ethyl ester hydrochloride.

1. additionAfter addition
2. temperaturethe suspension was heated
3. temperatureat reflux temperature for 2 h
4. filtrationThe mixture was filtered hot
5. filtrationFiltration and evaporation in vacuo
6. customafforded an oil, which
7. customwas crystallised
8. additionEthanol (10 ml) was added
9. additionfollowed by slow addition of diethyl ether (150 ml)
10. filtrationThe precipitated solid was filtered off
11. washwashed with diethyl ether
12. customdried by suction