Methyl 4-(4-hydroxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate

In the title molecule, C13H14N2O3S, the dihydropyrimidine ring is in a flattened sofa conformation, with the methine C atom forming the flap. The dihedral angle between the mean plane of the five essentially planar atoms of the dihydropyrimidine ring [maximum deviation = 0.056 (4) Å] and the benzene ring is 89.4 (2)°. The O atom of the carbonyl group is in a trans conformation with respect to the C=C bond of the dihydropyrimidine ring. In the crystal, N—H⋯O and O—H⋯S hydrogen bonds connect molecules, forming a two-dimensional network parallel to (001).

In the title molecule, C 13 H 14 N 2 O 3 S, the dihydropyrimidine ring is in a flattened sofa conformation, with the methine C atom forming the flap. The dihedral angle between the mean plane of the five essentially planar atoms of the dihydropyrimidine ring [maximum deviation = 0.056 (4) Å ] and the benzene ring is 89.4 (2) . The O atom of the carbonyl group is in a trans conformation with respect to the C C bond of the dihydropyrimidine ring. In the crystal, N-HÁ Á ÁO and O-HÁ Á ÁS hydrogen bonds connect molecules, forming a twodimensional network parallel to (001).   Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x À 1; y; z; (ii) x; y þ 1; z; (iii) Àx þ 1; Ày; Àz þ 1.
NSB is thankful to the University Grants Commission (UGC), India for financial assistance. NF thanks the UGC for a research fellowship under the RFSMS scheme.

Comment
The title compound is a member of the dihydropyrimidines (DHPM) (Kappe, 2000), which have emerged as important target molecules for therapeutic and pharmacological properties such as anticarcinogenic (Mayer et al., 1999) and more recently these compounds have emerged as the integral backbones of several calcium channel modulators (Jauk et al., 2000), anti-hypertensive agents. The title compound was chosen for X-ray diffraction studies with the intention of eliciting structural information which could facilitate further understanding of structural requirements for improved biological activity.
The molecular structure of the title compound is shown in Fig. 1. The dihydropyrimidine ring is in a flattened sofa conformation with atom C4 forming the flap. The dihedral angle between the mean plane of the five essentially planar atoms (N1/N2/C5/C6/C7) of the dihydropyrimidine ring [maximum deviation 0.056 (4) Å for C4] and the benzene ring (C8-C13) is 89.4 (2)°. The oxygen atom of the carbonyl group is in a trans configuration with respect to the C5═C6 bond of the dihydropyrimidine ring. In the crystal, N-H···O and O-H···S hydrogen bonds connect molecules forming a two-dimensional network parallel to (001) (Fig. 2).

Experimental
A mixture of methyl acetoacetate (3.12 g, 25 mmol), 4-hydroxy benzaldehyde (3.02 g, 20 mmol), thiourea (1.83 g, 24 mmol) and LiBr (0.175 g, 2mM) in acetonitrile (25 ml) was heated under reflux for 5 h. After cooling, the reaction mixture was poured onto crushed ice. Stirring was continued for several minutes. The solid product was filtered, washed with cold water, dried and recrystallized from ethanol (yield 85%; m.p.485 K). Single crystals were grown from a chloroform solution of the title compound by slow evaporation at room temperature.   Part of the crystal structure with hydrogen bonds shown as dashed lines.

Refinement
Methyl 4-(4-hydroxyphenyl)-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 > 2σ(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.