5-Acetyl-4-(2-chlorophenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one

In the title molecule, C13H13ClN2O2, the heterocyclic ring adopts a flattened boat conformation with the plane through the four coplanar atoms making a dihedral angle of 89.16 (5)° with the benzene ring, which adopts an axial orientation. The carbonyl, acetyl and methyl groups each have an equatorial orientation. In the crystal structure, intermolecular N—H⋯O hydrogen bonds lead to a tape motif. The H atoms of the methyl group at position 6 are disordered over two positions of opposite orientation.

In the title molecule, C 13 H 13 ClN 2 O 2 , the heterocyclic ring adopts a flattened boat conformation with the plane through the four coplanar atoms making a dihedral angle of 89.16 (5) with the benzene ring, which adopts an axial orientation. The carbonyl, acetyl and methyl groups each have an equatorial orientation. In the crystal structure, intermolecular N-HÁ Á ÁO hydrogen bonds lead to a tape motif. The H atoms of the methyl group at position 6 are disordered over two positions of opposite orientation.

Experimental
A solution of acetylacetone (1.0012 g, 0.01 mol), 2-chlorobenzaldehyde (1.4057 g, 0.01 mol) and urea (0.90 g, 0.015 mol) was heated under reflux in the presence of calcium chloride (0.1109 g, 0.001 mol) for 5 h (monitored by TLC). After completion of the reaction, the reaction mixture was cooled to room temperature and poured into crushed ice. The solid product was filtered under suction and purified by column chromatography on silica gel. Elution with 1:1 (benzene:ethyl acetate v/v) gave the product in the pure form. Yield 0.79 g (88%).

Refinement
The N-bound H atoms were located in a difference Fourier map and refined isotropically, see Table 1 for bond distances.
The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93 − 0.98 Å and U iso (H) = 1.2 − 1.5 times U eq (C). The H atoms bound to the C6-methyl group were found to be disordered over two positions with equal weight.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of (I), showing the atom-numbering scheme and displacement ellipsoids drawn at the 30% probability level. H atoms are shown as small spheres of arbitrary radius.