Crystal structure of 1′-(2-methylpropyl)-2,3-dihydrospiro[1-benzothiopyran-4,4′-imidazolidine]-2′,5′-dione

In the title compound, C15H18N2O2S, the 2,3-dihydro-1-benzothiopyran ring adopts a sofa conformation and the hydantoin ring is twisted with respect to the benzene ring at 78.73 (17)°. In the crystal, pairs of N—H⋯O hydrogen bonds link the molecules into inversion dimers.


S1. Comment
The combinatorial generation of organic compound libraries has emerged as a powerful tool for drug discovery. Small substituted heterocyclic compounds play an important role in the development of biologically active substances by offering a high structural diversity. Among such heterocycles, particularly the hydantoin scaffold opens the possibility of different kinds and degrees of substitution. They have been the focus of attention as a ubiquitous moiety incorporated into compounds with numerous biological activities and therapeutic applications (Nefzi et al., 2002). A variety of combinatorial approaches have been described by which pharmacophoric groups were attached to such a relatively rigid scaffold (Park & Kurth, 2000). Therefore, the chemistry of multiple substituted hydantoins has newly attracted much interest, and traditional approaches have been combined with recently developed strategies. Hence as a part of our ongoing research on hydantoins (Manjunath et al., 2012;Hussein et al., 2014), the synthesis, characterization and the structural work of the title compound was undertaken and herein we report its crystal structure.
The hydantoin ring in the structure is planar within the experimental limits with a maximum deviation of 0.012 (2) Å for The study of torsion angles, asymmetric parameters and least-squares plane reveals that the 2,3-dihydro-1-benzothiopyran ring in the structure adopts envelope conformation with S1 atom deviating by 0.0851 (14)  The molecules are interlinked by N-H···O hydrogen bonds to form inverted dimers.

S2. Experimental
A solution of spiro[1-benzothiopyran-4,4′-imidazolidine]-2′,5′-dione (1.0 eq) in N,N-dimethylformamide was taken, anhydrous K 2 CO 3 (3.0 eq) was added to the solution and stirred for 10 min. 1-Bromo-2 methyl propane (1-1.1 eq) 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 supporting information sup-2 extracted with ethyl acetate. Finally water wash was given to the organic layer and 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 solvent.

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.  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.