4-{(Z)-(sec-Butylamino)(phenyl)methylene}-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one

In the title compound, C21H23N3O, the dihedral angles formed by the pyrazolone ring with two phenyl rings are 10.38 (8) and 76.94 (6)°. The sec-butylamino group is disordered over two positions, with refined site-occupancy factors of 0.730 (4) and 0.270 (4). The compound could potentially be ligand stabilized in the solid state in a keto–enamine tautomeric form. The amine functionality is involved in an intramolecular N—H...O hydrogen bond, while weak intermolecular C—H...O and C—H...N hydrogen bonds participate in the formation of the crystal structure