1008-79-3

General procedure for the synthesis of 1-phenyl-1H-pyrazol-3(2H)-one from phenanthrone: 1-phenylpyrrolidin-3-one (82.99 mmol, 1.0 eq.) was dissolved in 5% aqueous sodium hydroxide solution and iron chloride hexahydrate (16.60 mmol, 0.2 eq.) was added. The reaction system was kept at 80 °C under oxygen atmosphere. After completion of the reaction, water was added to the reaction mixture to quench the reaction and the pH was adjusted with hydrochloric acid to 1~2. The reaction mixture was extracted with ethyl acetate and the organic layer was washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure and the residue was purified by column chromatography (eluent ratio: petroleum ether:ethyl acetate = 2:1) to afford the light yellow solid product 1-phenyl-1H-pyrazol-3-ol (1.46 g, 11% yield).

[1] European Journal of Organic Chemistry, 2011, # 27, p. 5323 - 5330
[2] Tetrahedron, 2009, vol. 65, # 37, p. 7817 - 7824
[3] Dyes and Pigments, 2010, vol. 85, # 3, p. 79 - 85
[4] Bulletin of the Korean Chemical Society, 2010, vol. 31, # 11, p. 3341 - 3347
[5] Journal of Chemical Research, 2015, vol. 39, # 10, p. 594 - 600