(E)-3-(Benzo[b]thiophen-2-yl)-2-(3,4,5-trimethoxyphenyl)acrylonitrile and (Z)-3-(benzo[b]thiophen-2-yl)-2-(3,4-dimethoxyphenyl)acrylonitrile

The title compounds, C20H17NO3S, (I), and C19H15NO2S, (II), were prepared by the reaction of benzo[b]thio-phene-2-carbaldehyde with (3,4,5-trimethoxy- phenyl)-acetonitrile and (3,4-dimethoxy-phenyl)-acetonitrile, respectively, in the presence of methanolic potassium hydroxide. In (I), the C=C bond linking the benzo[b]thio-phene and the 3,4,5-trimethoxy-phenyl units has E geometry, with dihedral angles between the plane of the bridging unit and the planes of the two adjacent ring systems of 5.2 (3) and 13.1 (2)°, respectively. However, in (II), the C=C bond has Z geometry, with dihedral angles between the plane of the bridging unit and the planes of the adjacent benzo[b]thio-phene and 3,4-dimethoxy-phenyl units of 4.84 (17) and 76.09 (7)°, respectively. There are no significant inter-molecular hydrogen-bonding inter-actions in the packing of (I) and (II). The packing is essentially stabilized via van der Waals forces.