Sodium Hydroxide → 5-[2-(4-Chlorophenyl)-ethyl]1H-pyrazole-3-carboxylic acid

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Reaction Steps

Freshly prepared aq. NaOH (10 M in H2O, 16.31 mmol) was added to a stirring, room temperature solution of 68 (0.9092 g, 3.26 mmol) in MeOH (8.2 mL, 0.4 M) under N2. The reaction was then heated to reflux until the reaction was judged complete by HPLC (7 min). The reaction was concentrated, redissolved in H2O (5 mL), and extracted with EtOAc (2 mL). 10% aq. HCl was added dropwise to the aqueous layer until the pH=2. The white solid that precipitated was filtered off and washed with cold H2O. The solid was dried under vacuum overnight to obtain 0.7543 g (92.2%) of 69. Since 69 still contained a very small amount of an impurity, it was dissolved in 38 mL of toluene with 10 mL of EtOAc and 14 mL of EtOH while heating to reflux. Pure white solid precipitated from the reaction after sitting overnight (0.4052 g). solid (Note: An undesired impurity has a retention time of 9.904 min by HPLC). 1H (CD3OD, 400 MHz): δ 7.24 (2H, d, J=8.3 Hz), 7.15 (2H, d, J=8.3 Hz), 6.54 (1H, s), 2.95 (4H, s) ppm. 13C (CD3OD, 100 MHz): δ 164.68, 148.23, 142.84, 140.91, 133.00, 131.08, 129.46, 107.59, 35.83, 28.78 ppm. DEPT (CD3OD, 100 MHz): CH2 carbons: 35.83, 28.78; CH carbons: 131.08, 129.46, 107.59 ppm. HPLC: 9.026 min.

Provenance & Evidence