Hydrazine hydrate (1:1) → 3-phenyl-1H-pyrazol-4-amine

Participants

Reaction Steps

A 250 ml round-bottomed flask is charged at RT with 20.5 g of a mixture of the E and Z isomers of 2-[1-(dimethylamino)-3-oxo-3-phenylprop-1-en-2-yl]-1H-isoindole-1,3(2H)dione in 75 ml of ethanol. 7.8 ml of hydrazine hydrate are added. The suspension is stirred at RT for 1 h 30 min and then heated to reflux. After 1 h 30 min of heating, a thickening of the mixture may be observed, and it takes on a yellow colour. The suspension is filtered off hot with suction on a frit and the precipitate is washed with ethanol. The filtrate is concentrated under RP. The product is purified by flash chromatography on silica gel (15-40 μm), eluting with DCM and with a DCM/methanol mixture (95/5 by vol.), to give 9.45 g of 5-phenyl-1H-pyrazol-4-amine (brown solid). LC-MS-DAD-ELSD: 163 (+)=(M+H)(+).

Provenance & Evidence