Acetic Acid → tert-Butyl 4-cyclopropylpiperazine-1-carboxylate

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A solution of tert-butyl piperazine-1-carboxylate (9.31 g, 50 mmol), [(1-ethoxycyclopropyl)oxy]trimethylsilane (20.11 mL, 100.00 mmol) and acetic acid(14.31 mL, 250.00 mmol) in tetrahydrofuran (100 mL), methanol (10 mL) was treated with sodium cyanoborohydride (4.71 g, 75.00 mmol) at 20° C. The resulting solution was stirred at 60° C. for 18 h. The reaction mixture was cooled, filtered and evaporated to dryness. 1N HCl (40 ml) and water (60 ml) were added and the solution extracted with ethyl acetate (3×50 ml). The aqueous layer was basified to pH 10 with solid potassium carbonate and extracted with ethyl acetate (4×50 ml). The organic extracts were washed with saturated sodium chloride solution (50 ml) and dried over MgSO4, filtered and evaporated to dryness to give tert-butyl 4-cyclopropylpiperazine-1-carboxylate (7.73 g, 68.3%) as a white waxy solid.

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