Triethylamine → 1,1-Dimethylethyl 4-[(4-methyl-1-piperazinyl)carbonyl]-1-piperidinecarboxylate

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Reaction Steps

The solution of 1-(tert-butoxycarbonyl)-4-piperidinecarboxylic acid (Aldrich) (21.88 g, 95.4 mmol), triethylamine (13.3 mL, 95.4 mmol) and HBTU [O-benzotriazol-1-yl-N,N,N′,N′-tetramethyluronium hexafluorophosphate (Advanced Chem. Tech.)] (38.36 g, 101.0 mmol) in dry dimethylformamide (100 mL) was stirred at room temperature for five minutes before N-methyl-piperazine (10.6 mL, 95.5 mmol) was added. The pH of the reaction mixture was adjusted to 8 by the addition of triethylamine, the so obtained mixture was stirred at room temperature overnight, then concentrated in vacuo. The residue was treated with saturated sodium hydrogencarbonate solution (350 mL), extracted with ethyl acetate (3×250 mL), the combined organic layers were washed with saturated sodium hydrogencarbonate solution, water and brine, dried over sodium sulfate, filtered and concentrated. The residue was submitted to column chromatography using Kieselgel 60 (0.040-0.063 mm) (Merck) as adsorbent, and chloroform:methanol=9:1 as eluent to yield 25.8 g (87%) of the title compound as an oil.

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