Sulfuric Acid → Ethyl 5-amino-1-phenyl-1H-pyrazole-3-carboxylate

Participants

Reaction Conditions

Reaction Steps

Phenyl hydrazine (2.94 ml, 0.03 moles) was dissolved in water (50 ml) in a 500 ml beaker. Concentrated H2SO4 (1.63 ml, 0.03 mole) was added drop-wise using a pipette while cooling with ice water bath. This phenyl hydrazine solution was then added to a stirred solution of sodium ethyl cyanopyruvate (5.37 g, 0.03 mole) in 70 ml of chloroform in a 500 ml round bottom flask at room temperature. Stirring was maintained for about 24 hrs and the reaction was monitored by LCMS. After the completion of reaction, the organic layer was separated and the aqueous layer was extracted with CHCl3 (2×150 ml). The combined organic layer was then washed with saturated NaHCO3 (1×100 ml), dried over sodium sulfate. Removal of solvent provided a viscous oil which was mainly non-cyclized hydrazone. The crude product was dissolved in minimum amount of dry EtOH (15 ml) and the mixture was heated in sealed tube at 120-150° C. for overnight. After the completion of reaction, ethanol was evaporated in vacuo to give crude product, which was purified by column chromatography eluting with Hexanes/Ethyl Acetate=9/1 to 1/1 to give 5.54 g of 5-Amino-1-phenyl-1H-pyrazole-3-carboxylic acid ethyl ester (yield: 80%).

Provenance & Evidence