Thionyl Chloride → 3-(1-Acetyl-4-piperidinyl)propionyl chloride

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Reaction Steps

3-(1-Acetyl-4-piperidinyl)propionic acid (4.0 g, 20.0 mmol) was added portionwise to thionyl chloride (2.0 ml) with ice-bath cooling. After the mixture was stirred for 5 minutes, the excess thionyl chloride was distilled off and the residue was washed with hexane to give 3-(1-acetyl-4-piperidinyl)propionyl chloride as light-yellow solid. Aluminum chloride (8.3 g, 62.2 mmol) powders were added in small portions to a mixed solution of the above acid chloride and 5-formyl-5,6,11,12-tetrahydrobenz[bf]azocine (4.0 g, 16.85 mmol), obtained in Example 5, in 1,2-dichloroethane (15 ml) with ice-bath cooling. This mixture was stirred at room temperature for 16 hours, then poured in ice-water, and extracted with-ethyl acetate. The extract was washed with saturated NaCl/H2O and dried over MgSO4 and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate-methanol=20:1) to provide 3-(1-acetyl-4-piperidinyl)-1-(5-formyl-5,6,11,12-tetrahydrodibenz[bf]azocin-8-yl)-1-propanone (6.5 g) as light yellow oil.

Provenance & Evidence