Ethyl 5-amino-1-(6-chloro-pyridazin-3-yl)-1H-pyrazole-4-carboxyl-ate.

In the title compound, C(10)H(10)ClN(5)O(2), the dihedral angle between the aromatic rings is 0.16 (9)°. Two S(6) ring motifs are formed due to intra-molecular N-H⋯N and N-H⋯O hydrogen bonds.

N-(4-Methyl-phen-yl)-6-(pyrazol-1-yl)pyridazin-3-amine.

In the title compound, C(14)H(13)N(5), the pyrazole ring is disordered over two orientations in a 0.571 (10):0.429 (10) ratio and the dihedral angle between the pyridazine ring and the benzene ring is 28.

3-Chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridazine.

In the title compound, C(9)H(9)ClN(4), the dihedral angle between the aromatic rings is 6.25 (9)°. The whole mol-ecule is approximately planar (r.