Synthesis
At room temperature, 4-iodopyrazole (20 mmol) was dissolved in THF (60 mL) and Et3N (30 mmol) and di-tert-butyl dicarbonate (Boc) 2O (22 mmol) were added sequentially. After 2 hours of reaction, N-Boc-4-iodopyrazole (5.88 g, 100% yield) was obtained. Subsequently, N-Boc-4-iodopyrazole was dissolved in THF (100 mL) under nitrogen protection, Pd(Ph3P)4 (1.1 g, 1 mmol) and hexamethyldistannane (20 mmol) were added, and the reaction was carried out at 78 °C overnight. After completion of the reaction, 10% KF aqueous solution was added, stirred for 30 min and filtered through a diatomaceous earth pad. The filtrate was extracted with EtOAc, the organic layer was washed with water and dried over MgSO4. After filtration and concentration, it was purified by column chromatography to give 3-trimethylstannopyrazole derivative (5 g, 75% yield) as a white solid.
References
[1] Patent: EP946508, 2009, B1. Location in patent: Page/Page column 58
[2] Patent: WO2012/123745, 2012, A1. Location in patent: Page/Page column 64
[3] Angewandte Chemie - International Edition, 2013, vol. 52, # 32, p. 8290 - 8294
[4] Angew. Chem., 2013, vol. 125, # 32, p. 8448 - 8452,5
[5] Journal of Medicinal Chemistry, 2013, vol. 56, # 24, p. 10045 - 10065
