Hydrochloric Acid → 4-[(2-benzyloxyphenyl)methyl]-1,2-dihydro-5-isopropyl-3H-pyrazol-3-one

Participants

Reaction Conditions

Reaction Steps

To a solution of 2-benzyloxybenzyl alcohol (2.1 g, 9.42 mmol) in tetrahydrofuran (10 mL), triethylamine (1.38 mL, 9.89 mmol) and methanesulfonyl chloride (0.766 mL, 9.89 mmol) were added under ice cooling and stirred at room temperature for 30 minutes. After filtration to remove the insoluble materials, the filtrate was concentrated to give (2-benzyloxyphenyl)methyl mesylate (3.24 g). To a suspension of methyl isobutyrylacetate (1.43 g, 9.89 mmol), sodium hydride (60% in oil; 396 mg, 9.89 mmol) and dimethoxyethane (10 mL), a solution of (2-benzyloxyphenyl)methyl mesylate (3.24 g) in dimethoxyethane (10 mL) was added and stirred at 70° C. overnight. After addition of 0.5 M HCl, the reaction mixture was extracted twice with ethyl acetate. The combined organic layers were washed with saturated aqueous sodium chloride and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure to give an oil. To this oil, toluene (20 mL) and hydrazine monohydrate (317 mg, 9.89 mmol) were added and the resulting mixture was heated under reflux for 3 hours. After cooling to room temperature, the reaction mixture was diluted with ethyl acetate, washed with water and dried over anhydrous magnesium sulfate. The reaction mixture was concentrated and the resulting residue was purified by silica gel column chromatography (chloroform:methanol=50:1 to 8:1) to give the titled compound (750 mg, 25%) as a light-yellow amorphous substance.

Provenance & Evidence