The title compound, C19H17N3O3S (I), was prepared by a [3 + 2]cyclo-addition azide condensation reaction using sodium azide and l-proline as a Lewis base catalyst. N-Methyl-ation of compound (I) using CH3I gave compound (II), C20H19N3O3S. The benzo-thio-phene ring systems in (I) and (II) are almost planar, with r.m.s deviations from the mean plane = 0.0205 (14) in (I) and 0.016 (2) Å in (II). In (I) and (II), the triazole rings make dihedral angles of 32.68 (5) and 10.43 (8)°, respectively, with the mean planes of the benzo-thio-phene ring systems. The trimeth-oxy phenyl rings make dihedral angles with the benzo-thio-phene rings of 38.48 (4) in (I) and 60.43 (5)° in (II). In the crystal of (I), the mol-ecules are linked into chains by N-H⋯O hydrogen bonds with R (2) 1(5) ring motifs. After the N-methyl-ation of structure (I), no hydrogen-bonding inter-actions were observed for structure (II). The crystal structure of (II) has a minor component of disorder that corresponds to a 180° flip of the benzo-thio-phene ring system [occupancy ratio 0.9363 (14):0.0637 (14)].
Keywords: anti-cancer agent; combretastatin A-4 analog; crystal structure; hydrogen bonding; triazole ring.