Synthesis
Under nitrogen protection, 4-iodo-1H-pyrazole (1.58 g, 8.0 mmol) was dissolved in anhydrous tetrahydrofuran and added dropwise to a freshly prepared suspension of sodium hydride (0.21 g, 8.7 mmol). The reaction mixture was stirred at room temperature for 3 h. Then iodomethane (1.0 mL, 2.24 g, 15.8 mmol) was slowly added dropwise. Stirring of the reaction mixture was continued for 12 h. The reaction was subsequently quenched by the addition of about 50 mL of water. The crude product was extracted with ether and the organic phase was dried over anhydrous sodium sulfate. Concentration under reduced pressure to remove the solvent gave 1-methyl-4-iodo-pyrazole as a pale yellow solid. Yield: 1.64 g, 98% yield.
References
[1] Heterocycles, 2018, vol. 96, # 7, p. 1203 - 1215
[2] Patent: US6797723, 2004, B1. Location in patent: Page/Page column 97
[3] Patent: WO2014/22128, 2014, A1. Location in patent: Paragraph 0186
[4] Patent: CN103539777, 2016, B. Location in patent: Paragraph 0455;0456
[5] Patent: WO2012/123745, 2012, A1. Location in patent: Page/Page column 70
