1,3-Bis(1-cyclohexylethyl)imidazolidine-2-thione

The complete molecule of the title compound, C19H34N2S, is generated by crystallographic twofold symmetry, with the C=S group lying on the rotation axis. A short C—H⋯S contact occurs in the molecule. The five-membered ring is twisted and the cyclohexyl ring adopts a chair conformation. The dihedral angle between the mean plane of the five-membered ring and the basal plane of the cyclohexyl ring is 75.32 (13)°.

The complete molecule of the title compound, C 19 H 34 N 2 S, is generated by crystallographic twofold symmetry, with the C S group lying on the rotation axis. A short C-HÁ Á ÁS contact occurs in the molecule. The five-membered ring is twisted and the cyclohexyl ring adopts a chair conformation. The dihedral angle between the mean plane of the fivemembered ring and the basal plane of the cyclohexyl ring is 75.32 (13) .
The molecule has twofold symmetry about the C═S (C1═S1) of imidazolidinethione and therefore, the asymmetric unit is half of the molecule. The asymmetric part of imidazolidinethione moiety A (S1/C1/N1/C2) and the basal plane of cyclohexyl ring B (C6/C7/C9/C10) are almost planar with r.m.s. deviations of 0.036 and 0.004 Å, respectively. The dihedral angle between A/B is 75.32 (13)°. The cyclohexyl adopts chair conformation with apical C-atoms C5 and C8 at a distance of -0.651 (5) and 0.638 (8) Å, respectively from the basal plane B. There exist weak intramolecular H-bondings of C-H···S type (Table 1, Fig. 1) and form S(5) ring motif. No other interaction is found in the crystal.

Experimental
(S)-1-cyclohexylethanamine (2.5 equiv.) and 1,2-dibromoethane (1 equiv.) were placed in a pressure vessel and heated at 393 K for 5 h, during which the reaction mixture solidified. The system was cooled to room temperature and NaOH (1 N, 20 ml) and ethyl acetate (20 ml) were added in to the reaction mixture. After dissolving the reaction mixture, the crude product was extracted with ethyl acetate (3 × 25 ml). The combined organic layers were concentrated and subjected to column chromatography. The product obtained from column chromatography (1 equiv.) was added to toluene (0.4 M) in pressure vessel and thiocarbonyldiimidazol (1.1 equiv.) was added to it. This mixture was heated about 373 K for 15 h.
Again the extraction with ethyl acetate (3 × 25 ml) was carried out by using column chromatography to get the required product. Yield: 90%. Colourless prisms of (I) were obtained by recrystallizing from methanol after 48 h.

Refinement
The H atoms were positioned geometrically (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = xU eq (C), where x = 1.5 for methyl and x = 1.2 for all other H atoms.

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009  View of the title compound with displacement ellipsoids drawn at the 50% probability level. The dotted lines indicate the short C-H···S contacts. 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 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.