4-Nitro-1-(tetrahydropyran-4-yl)-1H-pyrazole (1.59 g, 8.07 mmol) was used as the starting material and mixed with 10% palladium/carbon catalyst in ethanol (30 mL). The reaction mixture was stirred overnight under hydrogen atmosphere. Upon completion of the reaction, the catalyst was removed by filtration through diatomaceous earth and the filtrate was subsequently concentrated to afford the target compound 1-tetrahydro-2H-pyran-4-yl-1H-pyrazol-4-amine as a purple solid (1.33 g, 98% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 1.76-1.94 (m, 4H), 3.29-3.48 (m, 2H), 3.80 (br.s, 2H), 3.84-4.00 (m, 2H), 4.16 (tt, J = 10.42, 5.38 Hz, 1H), 6.90 (s, 1H), and 7.06 (s, 1H); mass spectrum (ES + APCI+): m/z 168 [M+H]+.
