3-Methyl-1,2,3,4,5,6,1′,2′,3′,4′-decahydrospiro[benz[f]isoquinoline-1,2′-naphthalen]-1′-one

The title compound, C23H23NO, is the product of a tandem transformation of the double Mannich base bis(1-oxo-1,2,3,4-tertrahydro-2-naphthoylmethyl)amine hydrochloride in HBr solution upon heating. The tetrahydropyridine ring has a non-symmetrical half-chair conformation, whereas the cyclohexadiene and cyclohexene 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, molecules form [001] chains via weak non-classical C—H⋯N hydrogen bonds. The chains are stacked along the b axis.

The title compound, C 23 H 23 NO, is the product of a tandem transformation of the double Mannich base bis(1-oxo-1,2,3,4tertrahydro-2-naphthoylmethyl)amine hydrochloride in HBr solution upon heating. The tetrahydropyridine ring has a nonsymmetrical half-chair conformation, whereas the cyclohexadiene and cyclohexene 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, molecules form [001] chains via weak non-classical C-HÁ Á ÁN hydrogen bonds. The chains are stacked along the b axis.

Khrustalev Comment
The double Mannich bases, obtained in the form of hydrochlorides from acetophenones, formaldehyde and alkylamines by heating in HCl solution, can be easily cyclized under action of bases yielding 3-aroyl-4-arylpiperidin-4-ols (Plati & Wenner, 1949). The latter are intermediate products in the synthesis of important antihistaminic agents (Plati & Wenner, 1950;Ellefson et al., 1978). We have synthesized an analogous double Mannich base -bis(1-oxo-1,2,3,4-tertrahydro-2naphthoylmethyl)amine hydrochloride from α-tetralone and tried to prepare from it the corresponding γ-piperidol derivative by the same way. But, instead, multicomponent mixture was formed which contained only traces of the desirable derivative (as identified by LC-MS method). However, we have found that the expected product of the cyclization in the dehydrated form (Plati & Wenner, 1950;Soldatenkov et al., 2008Soldatenkov et al., , 2009Soldatova et al., 2010) is formed by heating of our double Mannich base in HBr solution (Fig. 1). It can be suggested that the starting reagent undergoes a tandem transformation. The first step of this process is aldol-type intramolecular cycloaddition of the two cyclohexenone moieties to each other, and the second one is dehydration. The structure of the product -spiro-N-methylhexahydrobenzo[f]isoquinoline-1,2′-(tetrahydronaphthalin-1′-one), C 23 H 23 NO, (I) was unambiguously established by Xray diffraction study.
The tetrahydropyridine ring has a nonsymmetrical half-chair conformation (the C2 and N3 atoms are out of the plane through the other atoms of the ring by 0.612 (3)Å and -0.136 (3)Å, respectively), whereas the cyclohexadiene and cyclohexene rings adopt nonsymmetrical half-boat conformations (the C4A and C5 carbon atoms are out of the plane through the other atoms of the ring by 0.423 (3) and 0.814 (3) Å, respectively, in the case of the cyclohexadiene ring, and the C1 and C3′ carbon atoms are out of the plane through the other atoms of the ring by 0.232 (3)Å and 0.756 (3)Å, respectively, in the case of the cyclohexene ring). The dihedral angle between the planes of the terminal benzene rings is 62.85 (6)°.
The nitrogen N3 atom has a trigonal-pyramidal geometry (sum of the bond angles is 332.4 (3)°).
In the crystal, the molecules of I form the chains toward [0 0 1] by the weak non-classical intermolecular C9-H9···N3 i hydrogen bonding interactions (Fig. 3, Table 1). The crystal packing of the chains is stacking along the b axis. Symmetry code: (i) x, 1-y, -1/2+z. The molecule of I possesses an asymmetric center at the C1 carbon atom. The crystal of I is racemate.

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.95Å-0.99Å and refined in the riding model with fixed isotropic displacement parameters (U iso (H) = 1.5U eq (C) for the methyl group and 1.2U eq (C) for the other groups).

Figure 1
The preparation of the title product by a tandem transformation of bis(1-oxo-1,2,3,4-tertrahydro-2-naphthoylmethyl)amine hydrochloride.   Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.