1,4-Dimethyl-3-phenyl-3H-pyrazolo[3,4-c]isoquinolin-5(4H)-one

The title compound, C18H15N3O, is the product of the thermal decomposition of the diazonium salt derived from 2-amino-N-methyl-N-(3-methyl-1-phenyl-1H-pyrazol-5-yl)benzamide. It is characterized by a trans orientation of the methyl groups with respect to the tricyclic ring system. The molecule has a nearly planar phenylpyrazolo[3,4-c]isoquinolin-5-one system, the largest deviation from the mean plane being 0.066 (2) angstrom for the O atom. The dihedral angle between the phenyl substituent and the heterotricycle is 67 (1)degrees. The packing is stabilized by C-H center dot center dot center dot N hydrogen-bond interactions, with the formation of molecular chains along the c axis.