Hydrochloric Acid → 4-[(E)-3-(3,4-Dichloro-phenyl)-acryloyl]-3-methyl-1-pent-4-enyl-piperazin-2-one

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Reaction Steps

Hydrogen chloride solution (4 M in 1,4-dioxane, 8 ml) was added to a solution of 2-methyl-3-oxo-4-pent-4-enyl-piperazine-1-carboxylic acid tert-butyl ester (200 mg, 0.71 mmol). The reaction mixture was stirred at room temperature for 3.5 h, then volatile material was removed by rotary evaporation. The residue was taken up in dichlormethane (10 ml), treated with 4-methylmorpholine (358 mg, 3.54 mmol), and the mixture obtained concentrated in vacuo. The residue was taken up in N,N-dimethylformamide (8 ml), then 4-methylmorpholine (358 mg, 3.54 mmol), 3,4-dichlorocinnamic acid (161 mg, 0.71 mmol), and O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluoro-phosphate (404 mg, 1.06 mmol) were added. The solution was stirred at room temperature for 48 h, then the mixture was partitioned between water and ethyl acetate. The organic layer was washed with brine, dried (MgSO4), and evaporated. Chromatography (SiO2; heptane-ethyl acetate gradient) produced the title compound (233 mg, 86%). Light yellow oil, MS (ISP)=381.2 (M+H)+.

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