N-(TERT-BUTOXYCARBONYL)-1 H-PYRAZOLE-1-CARBOXAMIDINE

24424-99-5

4023-02-3

152120-61-1

GENERAL STEPS: 1H-pyrazole-1-carboxamidine hydrochloride (9.0 g, 61.5 mmol, 1.0 eq.) and 9.0 mL of water were added to a solution of di-tert-butyl dicarbonate (13.4 g, 61.5 mmol) in acetone (45 mL) at room temperature. Subsequently, a solution of K2CO3 (4.24 g, 30.6 mmol, 0.5 eq.) in water (12.0 mL) was added slowly dropwise for 30 minutes. After 2 hours of reaction, di-tert-butyl dicarbonate (1.35 g, 6 mmol, 0.1 equiv) was added supplementally and the reaction mixture was stirred overnight. After completion of the reaction, the acetone was removed by distillation under reduced pressure. The resulting white solid was dissolved in 30.0 mL of water and stirred at 0 °C for 30 min. The precipitated tert-butyl (imino(1H-pyrazol-1-yl)methyl)carbamate was collected by filtration, washed sequentially with water and hexanes, and finally dried under vacuum to afford N-Boc-1H-pyrazole-1-carboxamidine as a colorless solid (11.37 g, 88% yield). The product was characterized by 1H NMR (CDCl3, 400MHz): δ 9.06 (brs, 1H), 8.45 (d, J = 3.2Hz, 1H), 7.67 (d, J = 0.8Hz, 1H), 7.59 (brs, 1H), 6.39 (dd, J = 2.8, 1.6Hz, 1H), 1.54 (s, 9H).