Synthesis
In a 250 mL round bottom flask, 3,5-dimethyl-1H-pyrazole (0.5 g, 5 mmol), iodine (I2, 0.79 g, 30 mmol) and ceric ammonium nitrate (CAN, 1.71 g, 3 mmol) were dissolved in 70 mL of acetonitrile (CH3CN). The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, the solvent was removed by rotary evaporator. The residue was dissolved in ethyl acetate (AcOEt) and washed sequentially with 10% aqueous sodium thiosulfate (Na2S2O3) and saturated saline. The aqueous phase was extracted once more with ethyl acetate, all organic phases were combined, dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated to dryness to afford 1.15 g (100% yield) of crude 4-iodo-3,5-dimethyl-1H-pyrazole, which was used in the subsequent reaction without further purification.LC-MS (MH+): 223.
References
[1] Patent: WO2006/128692, 2006, A2. Location in patent: Page/Page column 76
[2] Canadian Journal of Chemistry, 1992, vol. 70, # 4, p. 1121 - 1128
[3] Tetrahedron Letters, 2005, vol. 46, # 40, p. 6833 - 6837
[4] Tetrahedron Letters, 2001, vol. 42, # 5, p. 863 - 865
[5] Synthesis, 2001, # 11, p. 1711 - 1715
