1′′-Allyl-5′′-(4-methoxybenzylidene)-7′-(4-methoxyphenyl)-1′,3′,5′,6′,7′,7a′-hexahydrodispiro[acenaphthylene-1,5′-pyrrolo[1,2-c][1,3]thiazole-6′,3′′-piperidine]-2,4′′(1H)-dione

In the title compound, C39H36N2O4S, the piperidine ring adopts a twisted half-chair conformation. In the pyrrolothiazole fused-ring system, the pyrrole ring adopts an envelope conformation (with the C atom bound to the thiazole ring being the flap atom) and the thiazole ring also exhibits an envelope conformation (with the N atom bound to the pyrrole ring as the flap). The molecular structure features a weak intramolecular C—H⋯O interaction. In the crystal, a C—H⋯O interaction forms a linear chain along the diagonal of the ac plane, generating a C(14) graph-set motif. A weak C—H⋯π interaction also occurs.

In the title compound, C 39 H 36 N 2 O 4 S, the piperidine ring adopts a twisted half-chair conformation. In the pyrrolothiazole fused-ring system, the pyrrole ring adopts an envelope conformation (with the C atom bound to the thiazole ring being the flap atom) and the thiazole ring also exhibits an envelope conformation (with the N atom bound to the pyrrole ring as the flap). The molecular structure features a weak intramolecular C-HÁ Á ÁO interaction. In the crystal, a C-HÁ Á ÁO interaction forms a linear chain along the diagonal of the ac plane, generating a C(14) graph-set motif. A weak C-HÁ Á Á interaction also occurs.
Piperidine ring systems are of immense interest in the pharmaceutical industry as they exhibit a wide range of biological activities (Guengerich et al., 1973;Puder et al., 2000). In view of its medicinal importance and in conjunction with our research interests, we synthesized the title compound and report here its X-ray structure.
In the title compound ( Fig.1) C 39 H 36 N 2 O 2 S, the piperidine ring adopts a twisted half chair conformation with atoms N2 and C2 deviating by -0.1919 (1) Å and -0.5644 (1) Å respectively from the least squares plane defined by other atoms (C1/C3/C4/C5). In the fused system, the thiazole ring adopts an envelope conformation with N1 atom as a flap atom, displaced by a -0.6085 (1) Å from the mean plane through the remaining atoms and the pyrrole ring adopts an envelope conformation with C10 atom as a flap atom, displaced by a 0.6545 (1) Å from the mean plane through the remaining atoms. The methyl group of the methoxy phenyl rings are in equtorial orientations as evidenced from the torsion angles C58-O1-C55-C56 = 172.59 (16) ° and C97-O2-C94-C93 = 172.07 (14) °. The methoxy phenyl rings are oriented at angles of 56.25 (1) ° (C52-C57) and 86.90 (1) ° (C91-C97) with the mean plane of the piperidine ring. The twist of the methoxyphenyl ring attached to C51 may be due to the non-bonded interactions between one of the ortho H atoms of the aryl ring and equtorial H atoms at the 2 position of the piperidine ring. The C-C bond lengths and C-C-C angles in the acenaphthylene group compare with those of related structure (Suresh et al.,2011).
The structure features a weak intra-molecular interaction. An inter-molecular C-H···O interaction forms a linear chain along the diagonal of the ac plane generating a graph set motif of C 1 1 (14) (Bernstein et al.,1995). In addition a weak C-H···π interaction (Table 1) is also observed.

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.