Crystal structure and Hirshfeld surface analysis of 7,7-dimethyl-2-phenyl-3,3a,4,6,7,8,9,9a-octahydro-1H-benzo[f]isoindole-1,5(2H)-dione

The crystal structure and Hirshfeld surface analysis of 7,7-dimethyl-2-phenyl-3,3a,4,6,7,8,9,9a-octahydro-1H-benzo[f]isoindole-1,5(2H)-dione obtained via the reaction of N-allyl-N-phenylacrylamide with 3-iodocyclohex-2-en-1-one using PdCl2(PPh3)2 as a catalyst,, is reported.


Chemical context
A cascade reaction is a chemical process that comprises at least two consecutive reactions such that each subsequent reaction occurs only by virtue of the chemical functionality formed in the previous step (Nicolaou et al., 2010;Jash et al., 2019;Knowles et al., 2021). Although cascade reactions have been successfully employed for the synthesis of the core skeleton of many important natural products, the design and performance of cascade reactions remain a challenging aspect of organic chemistry (Zhang et al., 2022;Xie & She, 2021). Meanwhile, alkylation of the position of enones and their derivatives has have drawn considerable attention (Krafft et al., 2005;Muimhneachá in et al., 2017;Shen & Huang, 2008;Zhang et al., 2010;Jana et al., 2021). McGlacken described a Pd-catalysed coupling procedure for tricyclic oxoisochromene derivatives, which represents an example of the arylation of activated carbocyclic enone-based substrates (Muimhneachá in et al., 2017). Huang and co-workers have realized a series of reactions including Sonogashira coupling, propargylallenyl isomerization, and [4 + 2] cycloaddition combined via alkylation of carbocyclic enone-based substrates, affording an efficient and stereoselective synthesis of polycyclic skeletons (Shen & Huang, 2008). Given this background, we report herein the synthesis and crystal structure of the title compound.

Figure 2
A packing diagram of the title compound. The C-HÁ Á Á and C-HÁ Á ÁO interactions are shown as dashed lines.

Figure 1
The molecular structure of the title compound, with the atom labelling and displacement ellipsoids drawn at the 50% probability level. H atoms are shown as small circles of arbitrary radii.

Figure 3
The Hirshfeld surface mapped over d norm in the range À0.2740 (red) to 1.7368 (blue) a.u.

Figure 4
The Hirshfeld surface mapped over shape-index.
actions. The fingerprint plots (Fig. 5) (Ma & Gu, 2006). In these two structures, the fused-ring systems are not planar. Compound I crystallizes in the monoclinic crystal system, space group P2 1 . The five-and six-membered rings are cisfused. The crystal structure is characterized by the presence of C-HÁ Á ÁO hydrogen bonds. Compound II crystallizes in the orthorhombic crystal system, space group Pbca. The molecules are linked by C-HÁ Á ÁO hydrogen bonds, and the crystal packing also features C-HÁ Á Á interactions.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were positioned geometrically with C-H = 0.93-0.98 Å and refined as riding atoms. The constraint U iso (H) = 1.2U eq (C) or 1.5U eq (Cmethyl) was applied in all case. Atoms C8 and C9 are disordered over two positions (A and B) in a 0.805 (10):0.195 (10) occupancy ratio.    (Rigaku OD, 2015); cell refinement: CrysAlis PRO (Rigaku OD, 2015); data reduction:

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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. The C(8) and C(9) is disordered over two positions, site occupancies were refined. This refinement led to a 0.805 : 0.195 ratio in occupancy over two positions for C(8)and C(9).