3-Methyl-1,2,3,4,5,6,1',2',3',4'-deca-hydro-spiro-[benz[f]isoquinoline-1,2'-naphthalen]-1'-one.

The title compound, C(23)H(23)NO, is the product of a tandem transformation of the double Mannich base bis-(1-oxo-1,2,3,4-tertrahydro-2-naphtho-ylmeth-yl)amine hydro-chloride in HBr solution upon heating. The tetra-hydro-pyridine ring has a non-symmetrical half-chair conformation, whereas the cyclo-hexa-diene and cyclo-hexene rings adopt non-symmetrical half-boat conformations. The dihedral angle between the planes of the terminal benzene rings is 62.85 (6)°. The N atom has a trigonal-pyramidal geometry [sum of the bond angles = 332.4 (3)°]. In the crystal, mol-ecules form [001] chains via weak non-classical C-H⋯N hydrogen bonds. The chains are stacked along the b axis.