General procedure for the synthesis of 4-(1H-pyrazol-4-yl)aniline from 4-(4-nitrophenyl)-1H-pyrazole: 4-(4-nitrophenyl)-1H-pyrazole (8.3 g, 43.88 mmol) was suspended in a mixed solvent of MeOH/DME (2:1 v/v) with the addition of 10% Pd/C (wet wt, 415 mg). The reaction flask was evacuated under vacuum and then filled with hydrogen (supplied via a balloon) and this process was repeated three times. The reaction mixture was stirred at room temperature and the reaction process was monitored by LC-MS for amine formation. After 2.5 hours of stirring, LC-MS and TLC analysis showed that a small amount of starting material was still present in the reaction. Additional catalyst (200 mg) was added to the reaction mixture and the reaction was recharged with hydrogen.The reaction was examined after 2 hrs and it was confirmed that the starting material had been completely consumed and the reaction was complete. The reaction mixture was filtered through diatomaceous earth and the diatomaceous earth was washed with MeOH. The filtrate was concentrated under reduced pressure to give 6.59 g of yellow solid product (94% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 12.68 (br s, 1H), 7.80 (s, 2H), 7.23 (d, J = 8.0 Hz, 2H), 6.54 (d, J = 8.0 Hz, 2H), 4.97 (s, 2H). Mass spectrum (ES+) m/z 160 ([M+H]+).
