Synthesis
1) Add 7.3 g (0.1 mmol) of N,N-dimethylformamide (DMF) to a 250 mL three-necked flask and cool in an ice water bath with stirring. 15.4 g (0.1 mmol) of phosphorus triclosan was slowly added dropwise and stirring was continued for 1 hour after completion of the drop. Subsequently, 2.88 g (0.02 mmol) of 1-phenylpyrazole was added and the reaction was heated to 100°C and refluxed for 3-6 h. The reaction was monitored by TLC.2) Upon completion of the reaction, the reaction mixture was poured into ice-water and the pH was adjusted to neutral with sodium carbonate solution. It was extracted with ethyl acetate (3 x 50 mL), and the combined organic phases were washed with 50 mL of saturated brine.3) The organic phase was purified by column chromatography (the eluent was a solvent mixture of ethyl acetate and petroleum ether (60-90°C), 1:5, v/v/v), and was concentrated under reduced pressure to give 3.10 g of the white solid product, 1-phenyl-1H-pyrazole-4-carbaldehyde, in 90.0% yield.
References
[1] Patent: CN107964007, 2018, A. Location in patent: Paragraph 0498
[2] Bioorganic and Medicinal Chemistry, 2009, vol. 17, # 1, p. 295 - 302
[3] Journal of Heterocyclic Chemistry, 1993, vol. 30, # 4, p. 957 - 960
[4] Patent: US2006/34786, 2006, A1. Location in patent: Page/Page column 62
[5] Synthetic Communications, 1998, vol. 28, # 7, p. 1299 - 1321
