3-(1,3-Diphenylpropan-2-yl)-4-methyl-6-phenylisoxazolo[3,4-d]pyridazin-7(6H)-one

In the title compound, C27H23N3O2, the geminal benzyl groups branching out from the methine adjacent to the isoxazole group are both syn-oriented to the methyl group of the pyridazinone moiety, as reflected by C-C distances of 3.812 (2) and 4.369 (2) angstrom between the methyl carbon and the nearest ring carbon of each benzyl group. This kind of conformation is retained in CDCl3 solution, as evidenced by distinct phenyl-shielding effects on the H-1 NMR signals of the methyl H atoms. The isoxazolo[3,4-d] pyridazin ring system is virtually planar (r.m.s. deviation from planarity = 0.031 angstrom), but the N-bonded phenyl group is inclined to the former by an ring-ring angle of 55.05 (3)degrees. In the crystal, the T-shaped molecules are arranged in an interlocked fashion, forming rodlike assemblies along [10 (1) over bar]. The molecules are held together by unremarkable weak C-H center dot center dot center dot N, C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions (C-O,N,C > 3.4 A), while significant pi-pi stacking interactions are absent.