Crystal structure of 1-ethylspiro[imidazolidine-4,1′-indane]-2,5-dione

In the title compound, C13H14N2O2, the C5 ring has an envelope conformation with the C atom adjacent to the quaternary C being the flap. The five atoms comprising the imidazolidine-2,4-dione ring are almost planar (r.m.s. deviation = 0.004 Å). The dihedral angle between the five-membered rings is 89.66 (10)°. In the crystal, inversion-related molecules are connected via {⋯HNCO}2 synthons. These are linked into a helical supramolecular chain along [010] by C—H⋯O interactions.


S1. Comment
The chemistry and properties of hydantoins and their derivatives have been investigated for more than 140 years. The hydantoin moiety which is present in various biologically active compounds is of immense pharmaceutical importance.
There has been considerable interest in the synthesis and characterization of hydantoin derivatives as an important class of heterocyclic compounds. Hydantoin derivatives that display interesting activities against a broad range of biological targets have been identified. Activity of hydantoin derivatives depends on the nature of substitution of hydantoin rings. As a part of our ongoing research on hydantoins (Manjunath et al., 2012), the synthesis, characterization and the structural work was undertaken on the title compound and herein we report its crystal structure.
The hydantoin ring in the structure is planar within experimental limits with a maximum deviation of 0.0036 (19) Å for C2 atom from the least squares plane of the hydantoin ring. The N-C bong lengths of N1-C2 = 1.394 (2) Å, N1-C5 = 1.367 (2) Å and N3-C2 = 1.337 (2) Å are comparable with the values reported earlier (Manjunath et al., 2011;Manjunath et al., 2012). The shortened bond length values can be attributed to the π-conjugation in the hydantoin ring.
The study of torsion angles, asymmetric parameters and least squares plane reveals that the five membered ring of the bicyclo octane moiety adopts envelope conformation with C4 atom deviating by 0.1121 (17) Å from the least-squares plane (Cremer & Pople, 1975). This is confirmed by the puckering amplitude Q = 0.2163 (19) Å. The hydantoin ring is in a equatorial position with the five membered ring which is evident by the dihedral angle value of 89.66 (10)°. The structure of the molecule is stabilized by the intermolecular hydrogen bonds of the type N-H···O and C-H···O (Table   1).

S2. Experimental
To a solution of 2, 3-dihydrospiro-[imidazoline-4-1-indene]-2,5-dione (1.0 eq) in N,N-dimethylformamide was added anhydrous K 2 CO 3 (3.0 eq) followed by stirring for 10 min. 1-Bromoethane (1-1.1eq) was then added. The reaction mixture was stirred at room temperature for 8 h and the progress of the reaction was monitored by TLC. Upon completion, the solvent was removed under reduced pressure and the residue was taken in water and extracted with ethyl acetate. Finally, the organic layer was washed with water and then dried over anhydrous sodium sulfate. The solvent was evaporated. The crude product was purified by column chromatography using chloroform:methanol (9:1) as an eluent.
Single crystals were obtained from slow evaporation of its ethylacetate solution.

S3. Refinement
The C-bound hydrogen atom were fixed geometrically (C-H = 0.93-0.97 Å) and allowed to ride on their parent atoms with U iso (H) = 1.2-1.5U eq (C). The N-bound H atom was included in the model with N-H = 0.86 Å, and with U iso (H) = 1.2U eq (N).

Figure 1
A view of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view along the b axis of the crystal packing of the title compound.  (13) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.