Synthesis
The general procedure for the synthesis of 4-iodopyrazole from pyrazole is as follows:
Example 1: Preparation of 2-amino-3-methyl-5-(1-methyl-1H-pyrazol-4-yl)-5-(3-pyrimidin-5-ylphenyl)-3,5-dihydro-4H-imidazol-4-one
Step a): Preparation of compound 2
A mixture of pyrazole (3.00 g, 44.0 mmol), iodine (6.71 g, 26.4 mmol) and ceric ammonium nitrate (14.5 g, 26.4 mmol) in acetonitrile (400 mL) was stirred at room temperature for 2.5 hours. Upon completion of the reaction, the mixture was concentrated and partitioned between ethyl acetate (250 mL) and 5% aqueous sodium bisulfite (250 mL). After addition of water (150 mL), the organic layer was separated, washed with brine (250 mL), dried over anhydrous magnesium sulfate, filtered and concentrated to afford compound 2 (7.80 g, 91% yield) as a white solid with a melting point of 105-108 °C.
1H NMR (300 MHz, CDCl3) δ 7.63 (s, 2H).
References
[1] Tetrahedron Letters, 2001, vol. 42, # 5, p. 863 - 865
[2] Heterocycles, 2003, vol. 60, # 4, p. 879 - 886
[3] Journal of Organic Chemistry, 2003, vol. 68, # 21, p. 8075 - 8079
[4] Tetrahedron Letters, 2001, vol. 42, # 11, p. 2089 - 2092
[5] Russian Chemical Bulletin, 2014, vol. 63, # 2, p. 360 - 367
