Synthesis
GENERAL METHOD: 2-Bromotoluene (1.0 mmol), pyrazole (1.5 mmol), LiOH (2.0 mmol), TBAB (0.2 mmol), activated Cu (0.1 mmol), and 2 mL H2O were added to a 10 mL flask. The mixture was heated in an oil bath at 120°C. After the reaction was completed, the mixture was cooled to room temperature and the product was extracted with ethyl acetate (10 mL × 3). The organic phases were combined, washed with brine (15 mL), dried over MgSO4, and concentrated under reduced pressure. Purification by silica gel column chromatography (petroleum ether/ethyl acetate, 5:1) afforded 1-o-tolyl-1H-pyrazole (colorless liquid, 88% yield).
References
[1] Advanced Synthesis and Catalysis, 2007, vol. 349, # 17-18, p. 2673 - 2676
[2] Journal of Organic Chemistry, 2004, vol. 69, # 17, p. 5578 - 5587
[3] Tetrahedron Letters, 2006, vol. 47, # 29, p. 5203 - 5205
[4] Chinese Journal of Chemistry, 2012, vol. 30, # 10, p. 2389 - 2393,5
[5] Tetrahedron Letters, 2013, vol. 54, # 15, p. 1994 - 1997
