Synthesis
In a 50 mL round bottom flask, 1-iodo-3-nitrobenzene (1.0 mmol), pyrazole (1.2 mmol), ligand (0.04 mmol), cuprous oxide (0.10 mmol), cesium carbonate (2.0 mmol), and dry solvent (20 mL) were added sequentially. The reaction system was placed under nitrogen protection. The reaction mixture was heated to the indicated temperature in an oil bath under continuous stirring and cooled to room temperature after 20 h of reaction. The reaction mixture was filtered through a porous filter funnel filled with diatomaceous earth and the filter cake was washed with ethyl acetate. If DMSO is used as solvent, the filtrate is washed three times with 25 mL of water for extraction. The organic phases were combined, dried with anhydrous magnesium sulfate, and concentrated under reduced pressure to remove the solvent to give the crude product. Finally, the crude product was purified by silica gel column chromatography, and the eluent was a solvent mixture of hexane and ethyl acetate in a volume ratio of 3:1.
References
[1] Journal of Organic Chemistry, 2007, vol. 72, # 23, p. 8969 - 8971
[2] Tetrahedron Letters, 2016, vol. 57, # 20, p. 2197 - 2200
[3] Angewandte Chemie, International Edition, 2009, vol. 48, # 40, p. 7398 - 7401
[4] Angewandte Chemie, 2009, vol. 121, # 40, p. 7534 - 7537
[5] Tetrahedron Letters, 2011, vol. 52, # 52, p. 7171 - 7174
