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A solution of 57.0 g. (0.5 mole) of 1-methyl-4-piperidinone and 106.0 g. (1.0 mole) of benzaldehyde in 400 ml. of ethanol is cooled in an ice bath and treated with HCl gas until 250 g. is absorbed. The red-colored solution is allowed to stand at room temperature overnight. The resulting deep red-brown solution is seeded, allowed to stand overnight at room temperature, and the crystalline solid is filtered on a sintered-glass funnel and washed with cold ethanol, followed by ether. After drying in a desiccator, the solid (146 g.) is digested in 400 ml. of hot ethanol (75°), cooled and filtered to give 120 g. of pale yellow product, m.p. 242-244° (dec.).

1. customis absorbed
2. waitto stand overnight at room temperature
3. filtrationthe crystalline solid is filtered on a sintered-glass funnel
4. washwashed with cold ethanol
5. customAfter drying in a desiccator
6. temperatureof hot ethanol (75°), cooled
7. filtrationfiltered
8. customto give 120 g