5′′-(2,4-Dichlorobenzylidene)-1′-(2,4-dichlorophenyl)-1′′-methyl-1′,2′,3′,5′,6′,7′,8′,8a’-octahydrodispiro[acenaphthylene-1,3′-indolizine-2′,3′′-piperidine]-2,4′′(1H)-dione

In the title compound, C37H30Cl4N2O2, the pyridinone ring adopts a twisted half-chair conformation. In the octahydroindolizine fused-ring system, the piperidine ring is in a chair conformation and the pyrrole ring is twisted about the C—N bond linking the five- and six-membered rings. The molecular structure features an intramolecular C—H⋯O interaction and the crystal packing is stabilized by C—H⋯π interactions.

In the title compound, C 37 H 30 Cl 4 N 2 O 2 , the pyridinone ring adopts a twisted half-chair conformation. In the octahydroindolizine fused-ring system, the piperidine ring is in a chair conformation and the pyrrole ring is twisted about the C-N bond linking the five-and six-membered rings. The molecular structure features an intramolecular C-HÁ Á ÁO interaction and the crystal packing is stabilized by C-HÁ Á Á interactions.

D-HÁ
In the title compound ( Fig. 1) the pyridinone ring adopts twisted half-chair conformation with atoms N1 and C5 deviating by -0.638 (2) and -0.465 (2) Å, respectively, from the least-squares plane defined by the other atoms (C2/C3/C4/C6). Within the octahydroindolizine fused ring system, the piperidine ring is in a chair conformation and the pyrrole ring is twisted about the N2-C8 bond. The C-C bond lengths and C-C-C angles in the acenaphthylene group compare with those of related structures (Hazell & Hazell, 1977;Hazell & Weigelt, 1976;Jones et al., 1992;Sundar et al., 2002). The observed conformation of the pyrrole ring may be due to the presence of an intramolecular C8 -H8···O2 interaction ( Table 1). The dihedral angle between the dichlorobenzene rings is 67.2 (1)° and these rings form angles of 46.8 (1) and 68.6 (1)° with the acenaphthene group, respectively. The sum of the bond angles at N2 of the pyrrole ring is 337.78°, indicating sp 3 -hybridization.

Refinement
H atoms were placed at calculated positions and allowed to ride on their carrier atoms with C-H = 0.93-0.98 Å, and U iso = 1.2U eq (C) for CH 2 and CH H atoms and U iso = 1.5U eq (C) for CH 3 H atoms.

Figure 1
The molecular structure of (I), showing 20% probability displacement ellipsoids and the atom-numbering scheme. Hatoms are omitted for clarity.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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.