Crystal structure of 3-benzyl-2-[( E )-2-(furan-2-yl)ethen-yl]-2,3-di-hydro-quinazolin-4(1 H )-one and 3-benzyl-2-[( E )-2-(thio-phen-2-yl)ethen-yl]-2,3-di-hydro-quinazolin-4(1 H )-one from synchrotron X-ray diffraction.

The chiral title compounds, C21 H18 N2 O2 , (I), and C21 H18 N2 OS, (II) - products of the three-component reaction between benzyl-amine, isatoic anhydride and furyl- or thienyl-acrolein - are isostructural and form isomorphous racemic crystals. The tetra-hydro-pyrimidine ring in (I) and (II) adopts a sofa conformation. The amino N atom has a trigonal-pyramidal geometry [sum of the bond angles is 347.0° for both (I) and (II)], whereas the amido N atom is flat [sum of the bond angles is 359.3° for both (I) and (II)]. The furyl- and thienylethenyl substituents in (I) and (II) are planar and the conformation about the bridging C=C bond is E . These bulky fragments occupy the axial position at the quaternary C atom of the tetra-hydro-pyrimidine ring, apparently, due to steric reasons. In the crystals, mol-ecules of (I) and (II) form hydrogen-bonded helicoidal chains propagating along [010] by strong inter-molecular N-H⋯O hydrogen bonds.