Yield:446276-22-8 91%

Reaction Conditions:

with hydrazine hydrate in ethanol; for 4 h;Reflux;Inert atmosphere;

Steps:

4.2. Preparation of 3-biphenyl-4-yl-1H-pyrazole

A mixture of 1-biphenyl-4-yl-3-dimethylamino-propenone (1.6 g, 6.4 mmol), ethanol (10 mL) and hydrazine hydrate (2 mL) was then refluxed for 4 h. After cooling to room temperature, the volatile species were removed in vacuo. The remaining yellow oil was re-dissolved in EtOH (20 mL) and the solution was dried over MgSO₄. The solvent was removed in vacuo to obtain a light yellow solid, which was recrystallized from toluene at -10 °C, giving colorless crystals. Yield: 1.27 g (91%). ¹H NMR (400 MHz, CDCl₃, ppm): δ 6.61 (s, 1H), 7.32 (t, J=7.2 Hz, 1H), 7.40 (t, J=7.2 Hz, 2H), 7.56-7.60 (m, 5H), 7.80 (d, J=8.0 Hz, 2H). ¹³C NMR (100 MHz, CDCl₃, ppm): δ 102.8, 126.4, 127.1, 127.6, 128.9, 131.2, 133.6, 133.6, 133.6, 140.7, 140.9. HRMS calcd for C₁₅H₁₂N₂ 220.1000, found 220.1007. Anal. Calcd for C₁₅H₁₂N₂: C, 81.79; H, 5.49; N, 12.72. Found: C, 81.32; H, 5.23; N, 12.82. IR (KBr disk, cm^-1): 3031(w), 2971(w), 1525(m), 1488(s), 1445(m), 1409(m), 1384(m), 1337(w), 1294(m), 1192(w), 1109(m), 1046(m), 1005(m), 954(s), 933(s), 841(s), 754(s), 722(m), 688(s), 608(m). Mp: 163.9-164.2 °C.

References:

Xu, Zhong-Lin;Li, Hong-Xi;Ren, Zhi-Gang;Du, Wei-Yuan;Xu, Wei-Chang;Lang, Jian-Ping [Tetrahedron,2011,vol. 67,# 29,p. 5282 - 5288] Location in patent:experimental part