General procedure for synthesis
4-bromo-5-(bromomethyl)-3-methyl-1-aryl-1H-pyrazole (AB1, AB2):
A mixture of 4-bromo-3,5-dimethyl-1-aryl-1H-pyrazole (11.5 mmol) and NBS
(66 mmol) in benzene (50 mL) was refluxed for 4 day. The solution was
concentrated, reaction mixture was extracted with EtOAc. After the
resulting residue was purified using column (EtOAc:hexane; 1:9)
4-bromo-5-(bromomethyl)-3-methyl-1-(p-tolyl)-1H-pyrazole (AB1):Yield 45%, white solid, 1H NMR (400 MHz,
CDCl3) δ 7.48 (d, J = 8.0 Hz, 2H), 7.42 (t,J = 8.0 Hz, 2H), 7.34 (t, J = 8.0 Hz, 1H), 4.33 (s, 2H),
2.23 (s, 3H).13C NMR (101 MHz, CDCl3)
δ 148.32, 139.02, 136.87, 129.46, 128.66, 124.70, 98.52, 77.42, 77.10,
76.78, 20.20, 12.26.
4-bromo-5-(bromomethyl)-1-(2,4-dinitrophenyl)-3-methyl-1H-pyrazole(AB2): Yield 55%, green solid, 1H NMR (400
MHz, CDCl3) δ 8.86 (t, J = 2.0 Hz, 1H), 8.65 (dt,J = 8.0, J = 2.0 Hz, 1H), 8.04 (dd, J = 8.0,J = 2.0 Hz, 1H), 4.43 (s, 2H), 2.29 (s, 3H).13C NMR (101 MHz, CDCl3) δ 151.41,
147.33, 146.05, 138.32, 136.71, 129.31, 127.76, 121.28, 100.64, 18.59,
12.31.