organic compounds
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The title compound, C20H19N3O, exists in a keto–enamine tautomeric form. The pyrazolone ring makes dihedral angles of 20.52 (10) and 77.73 (5)° with the two phenyl rings and an intramolecular N—HO hydrogen bond occurs. A weak intermolecular C—HO hydrogen bond is observed in the crystal structure. The allyl group is disordered over two positions, with site-occupancy factors of 0.533 (5) and 0.467 (5).