Crystal structure of 1′-ethylspiro[chroman-4,4′-imidazolidine]-2′,5′-dione: a hydantoine derivative

The title compound, C13H13N2O3, a hydantoin derivative, crystallized with two molecules (A and B) in an asymmetric unit. In molecule A, the imidazolidine ring is twisted about the C—N bond involving the spiro C atom, while in molecule B this ring is flat (r.m.s. deviation = 0.010 Å). The pyran rings in both molecules have distorted half-chair conformations. The mean plane of the imidazolidine ring is inclined to the aromatic ring of the chroman unit by 79.71 (11)° in molecule A and 82.83 (12)° in molecule B. In the crystal, pairs of N—H⋯O hydrogen bonds link the individual molecules to form A–A and B–B inversion dimers. The dimers are linked via N—H⋯O and C—H⋯O hydrogen bonds, forming sheets lying parallel to the bc plane, viz. (011). Within the sheets, the A and B molecules are linked by C—H⋯π interactions.

Considerable interest has been shown towards the synthesis and characterization of hydantoin derivatives which is a novel class of heterocyclic compounds. As a part of our ongoing research on hydantoins (Manjunath et al., 2011(Manjunath et al., , 2012, the synthesis, characterization and the structural work of the title compound was undertaken and herein we report on its crystal structure. The title compound, Fig. 1, an hydantoin derivative, crystallized with two molecules (A and B) in an asymmetric unit.
In molecule A the imidazolidine ring is twisted about the C9A-N2A bond, while in molecule B this ring is flat (r.m.s. deviation = 0.010 Å). The pyran rings of the chroman units in both molecules have distorted half-chair conformations.
The mean plane of the imidazolidine ring is inclined to the aromatic ring of the chroman unit by 79.71 (11) ° in molecule A and 82.83 (12) ° in molecule B.
In the crystal, pairs of N-H···O hydrogen bonds link the individual molecules to form A-A and B-B inversion dimers ( Fig. 2

S2. Synthesis and crystallization
A solution of 3-ethyl-5-(isochromon) imidazolidine-2, 4-dione (1.0 eq) in N,N-dimethyl formamide was taken, anhydrous K 2 CO 3 (3.0 eq) was added to the solution and stirred for 10 min. 1-bromo-ethane (1-1.1eq) was added. The reaction mixture was stirred at room temperature for 8 h and the progress monitored by TLC. Upon completion, the solvent was removed under reduced pressure and the residue was taken in water and extracted with ethyl acetate. The organic was washed with water and then and dried over anhydrous sodium sulfate. The solvent was evaporated and the crude product was purified by column chromatography using chloroform: methanol (9:1) as eluent.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The hydrogen atoms were fixed geometrically (N-H = 0.86 Å, C-H = 0.93-0.96 Å) and allowed to ride on their parent atoms with U iso (H) = 1.5U eq (C-supporting information sup-2 . E71, o705-o706 methyl) and 1.2U eq (N,C) for other H atoms.

Figure 1
A view of the molecular structure of the two independent molecules of the title compound, with atom labelling.
Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A viewed along the c axis of the crystal packing of the title compound (molecule A blue, molecule B red). The dashed lines represent hydrogen bonds (see Table 1; H atoms are shown as blue and red balls).  (2) 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 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.