1-Allyl-4-(1,3-benzothia-zol-2-yl)-5-methyl-2-phenyl-1H-pyrazol-3(2H)-one.

The title compound, C(20)H(17)N(3)OS, is a 1H-pyrazol-3(2H)-one having aromatic 4-(1,3-benzothia-zol-2-yl)- and 2-phenyl substituents. The five-membered ring and fused ring system are planar, the r.m.s. deviations being 0.021 and 0.005 Å, respectively. The five-membered ring is aligned at 7.9 (2)° with respect to the fused-ring system. The allyl and phenyl parts of the mol-ecule are both disordered over two positions in a 1:1 ratio. Weak inter-molecular C-H⋯O hydrogen bonding is present in the crystal structure.