Ethyl 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate

The title compound, C14H16N2O3, belongs to a group of esters of 2-oxo- and 1,2,3,4-tetrahydropyrimidine-5-carboxylic acids, which exhibit a wide spectrum of biological activities. The dihydropyrimidine ring adopts a screw-boat conformation. The crystal packing is stabilized by strong N—H⋯O and weak C—H⋯O intermolecular hydrogen bonds. An intramolecular C—H⋯O hydrogen bond is also present.

The title compound, C 14 H 16 N 2 O 3 , belongs to a group of esters of 2-oxo-and 1,2,3,4-tetrahydropyrimidine-5-carboxylic acids, which exhibit a wide spectrum of biological activities. The dihydropyrimidine ring adopts a screw-boat conformation. The crystal packing is stabilized by strong N-HÁ Á ÁO and weak C-HÁ Á ÁO intermolecular hydrogen bonds. An intramolecular C-HÁ Á ÁO hydrogen bond is also present.

Comment
The title compound belongs to the group of esters of 2-oxo and -1,2,3,4-tetrahydropyrimidine-5-carboxylic acids, which are known as `Biginelli compounds ' (Kappe et al., 1997). It has been suggested that the substituent effect may be attributable to intramolecular hydrogen bonding between the alkoxy oxygen and the proton of the pyrimidine ring NH group (Broughton et al., 1975). Several marine alkaloids having the dihydropyrimidine core unit have been found to show interesting biological activities, such as antiviral, antibacterial and anti-inflammatory (Overman et al., 1995). Many functionalized derivatives are used as calcium channel blockers and antihypertensive agents (Atwal et al., 1991). Against this background and in order to obtain detailed information on its molecular conformation, the structure of the title compound has been determined and the results are presented here.
The crystal packing is stabilized by strong N-H···O and C-H···O intermolecular hydrogen bonds (Table 1).

Experimental
A mixture of benzaldehyde (0.106 g, 1 mmol), ethyl acetoacetate (0.130 g, 1 mmol) and urea (0.070 g, 1.17 mmol) was ground with four drops of ortho phosphoric acid for about 30 minutes. The reaction mixture was cooled for 15 minutes and poured into a beaker containing 50 ml of cold water. The precipitate obtained was filtered, washed with water and ethanol to get white solid. Single crystals of the title compound suitable for X-ray diffraction were obtained by slow evaporation of a solution in ethanol (0.26 g, 92% yield; mp 203-204).

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent C atoms, with C-H distances fixed in the range 0.93-0.98 Å and N-H distance of 0.86 Å, with U iso (H) = 1.5U eq (C) for methyl H atoms and U iso (H) = 1.2U eq (C, N) for other H atoms.
supplementary materials sup-2 Figures   Fig. 1. The molecular configuration and atom-numbering scheme for (I). Displacement ellipsoids are drawn at the 50% probability level.