trans-4,5-Dihydroxy-1,3-bis(4-methoxyphenyl)imidazolidine-2-thione

In the title compound, C17H18N2O4S, where one of the N-4-methoxyphenyl fragments is disordered over two sets of sites, the five-membered ring exhibits a nearly half-chair conformation and the two hydroxyl groups lie on opposite sides of the five-membered ring. In the crystal, the molecules are linked into sheets parallel to (100) via O—H⋯O and O—H⋯S hydrogen bonds.

In the title compound, C 17 H 18 N 2 O 4 S, where one of the N-4methoxyphenyl fragments is disordered over two sets of sites, the five-membered ring exhibits a nearly half-chair conformation and the two hydroxyl groups lie on opposite sides of the five-membered ring. In the crystal, the molecules are linked into sheets parallel to (100) via O-HÁ Á ÁO and O-HÁ Á ÁS hydrogen bonds.
In analyzing the supramolecular structure of (I), for the sake of simplicity, we shall omit any consideration of the intermolecular C-H···O interactions involving a C-H bond from an aromatic ring, which is far too long to be significant.
Thus, molecules of (I) are linked into sheets by only two independent O-H···S and O-H···O hydrogen bonds (Table 1), the formation of which is readily analyzed in terms of two one-dimensional substructures. In the first substructure, hydroxyl atom O1 in the molecule at (x,y,z) acts as a hydrogen-bond donor to thiocarbonyl atom S1 in the molecule at (-x, y -1/2,-z + 3/2), so forming a C 2 2 (6) (Bernstein et al.,1995) chain along [010] and generated by 2 1 screw axis along (0,y,3/4) ( Fig.   2). Similarly in the second substructure, hydroxyl atom O2 in the molecule at (x,y,z) acts as a hydrogen-bond donor to supplementary materials sup-2 hydroxyl atom O1 in the molecule at (x,-y + 3/2,z + 1/2), so forming a C(5) (Bernstein et al., 1995) chain parallel to [001], this time generated by a 2 1 screw along (1/8,3/4,z) (Fig. 2). The combination of the two chain motifs is sufficient to link all the molecules into a sheet parallel to (100). Two such sheets pass through each unit cell; in each sheet, there are both enantiomers of (I); there are no direction-specific interactions between adjacent sheets, in particular C-H···π hydrogen bonds and π-π stacking interactions are absent.

Experimental
Into a three-necked round-bottomed flask equipped with a stirrer were introduced 1,3-bis(4-methoxyphenyl)thiourea(0.1 mol), glyoxal (40%, 18 g) and ethanol (95%, 30 ml). The mixture was then refluxed with stirring for ca 30 min and thereafter the solvent was removed; the residue was washed with cold ethanol and the resulting solid product was recrystallized from hot ethanol to give crystals of (I).

Refinement
The hydroxyl H atoms in (I) were found in a difference Fourier map and then freely refined. All other H atoms were positioned geometrically (aromatic C-H = 0.93 Å, methyl C-H = 0.96 Å, methyne C-H = 0.98 Å and O-H = 0.82 Å) and refined using a riding model [U iso (H) = 1.2U eq (aromatic and methyne C) and 1.5 U eq (methyl C and hydroxy O)].
The N2-containing (4-methoxyphenyl)imino group was found to be disordered, and therefore was modelled over two sets of positions, with a refined major occupancy of 0.747 (2). 10 Geometric displacement-parameter restraints were applied to the disordered part.  Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry codes: (i) -x,y -1/2,-z + 3/2; (ii) x + 1,-y + 3/2,z + 1/2; (iii) -x,y + 1/2,-z + 3/2; (iv) x,-y + 3/2,z + 1/2].  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-supplementary materials sup-4 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.