Ethyl 7-methyl-2-((1-methyl-1H-pyrrol-2-yl)methylene)-3-oxo-5-phenyl-3,5-dihydro-2H-thiazolo[3,2-a]pyrimidine-6-carboxylate

In the structure of the title compound, C22H21N3O3S, the thiazole ring forms dihedral angles of 88.83 (7) and 9.39 (9)°, respectively, with the benzene and pyrrole rings. The dihydropyrimidine ring adopts a flattened boat conformation. The olefinic double bond is in a Z conformation.

In the structure of the title compound, C 22 H 21 N 3 O 3 S, the thiazole ring forms dihedral angles of 88.83 (7) and 9.39 (9) , respectively, with the benzene and pyrrole rings. The dihydropyrimidine ring adopts a flattened boat conformation. The olefinic double bond is in a Z conformation.
In continuation of our studies on heterocyclic compounds, we report the crystal structure of the title compound. The fused thiazole ring has usual geometry as observed in other thiazolo[3,2-a]pyrimidine compounds (Hou, 2009;Zhao et al., 2011). The thiazole ring makes dihedral angles of 88.83 (7) and 9.39 (9)° with the benzene ring and pyrrole ring, respectively. The pyrimidine ring adopts a flattened boat conformation. The C2-C17 distance, 1.345 (2) Å, confirms this as a double bond and the molecule adopts a Z conformation with respect to this bond (Fig. 1).

Experimental
In a typical procedure of one pot Biginelli reaction, sulfamic acid (0.4 mol) was added to a solution of substituted benzaldehyde (0.5 mol), ethyl acetylacetate (0.6 mol), and thiourea (0.75 mol) in ethanol and reflux at 351 K for 2 h.
When the reaction was finished, the mixture was cooled to room temperature and filtered. The product ethyl 2mercapto-4-methyl-6 -phenyl-1,6-dihydropyrimidine-5-carboxylate was washed with water, and then dried in vacuum as a white solid.

Figure 1
The molecular structure of the title compound, showing 30% displacement ellipsoids for the non-hydrogen atoms.
Hydrogen atoms are drawn as spheres of arbitrary radius.

a]pyrimidine-6-carboxylate
Crystal data 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.45859 (