3-Amino-1-cyclopentyl-1H-pyrazole-4-carboxylic acid amide synthesis

Yield:959430-09-2 82%

Reaction Conditions:

Stage #1: ethyl 5-amino-1-cyclohexyl-1H-pyrazole-4-carboxylatewith sulfuric acid at 20; for 2 h;
Stage #2: with ammonia in water;

Steps:

Compound 12; 3-Amino-1-cyclopentyl-1H-pyrazole-4-carboxylic acid amide; To concentrated sulfuric acid (Fisher, 8 mL) at 0° C. was added 2 (4.24 g, 24.0 mmol) in small portions. The reaction was permitted to warm to room temperature and was stirred for two hours. At the end of this period all solid had dissolved. This viscous mixture was then added slowly (violent) to 100 mL concentrated ammonium hydroxide solution (Fisher). The mixture was stirred for ten minutes and the white solid that formed was collected by filtration, was washed with water, and was dried in vacuo. Yield: 3.838 g (82%). Compound 12: mp 179-181° C.; MS (ES⁺calculated: 194.24; found: 195.12 M+H). HPLC (100% purity, retention time 5.225 minutes-Method B); ¹H NMR (400 MHz, DMSO-d₆) δ 7.94 (s, 1H), 7.14 (br s, 1H), 6.67 (br s, 1H), 5.32 (br s, 2H), 4.39 (m, 1H), 1.97 (m, 2H), 1.83 (m, 2H), 1.72 (m, 2H), 1.61 (m, 2H).

References:

US2007/281949,2007,A1 Location in patent:Page/Page column 18