title: 4-[(Z)-(n-Butyl-amino)(phenyl)methyl-idene]-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one.
abstract: The title compound, C(21)H(23)N(3)O, exists in an enamine-keto form with the amino group involved in an intra-molecular N-H⋯O hydrogen bond. The dihedral angle between the phenyl rings is 73.59 (6)°. The five-membered ring is nearly planar, the largest deviation being 0.0004 (7) Å, and makes dihedral angles of 4.81 (6) and 69.81 (5)° wth the phenyl rings. In the crystal, pairs of weak C-H⋯O inter-actions link the mol-ecules into centrosymmetric dimers.
authors.affiliation: East China University of Science and Technology, College of Chemistry and Molecular Engineering, Mei Long Road 130, Shanghai 200237,  People's Republic of China.
authors.forename: Hai-Wen
authors.initials: HW
authors.lastname: Wang