Some chalcones derived from thiophene-3-carbaldehyde: Synthesis and crystal structures

Abstract

The synthesis, spectroscopic data and crystal and molecular structures of four 3-(3-phenylprop-1-ene-3-one-1-yl)thiophene derivatives, namely 1-(4-hydroxyphenyl)-3-(thiophen-3-yl)prop-1-en-3-one, C13H10O2S, (1), 1-(4-methoxyphenyl)-3-(thiophen-3-yl)prop-1-en-3-one, C14H12O2S, (2), 1-(4-ethoxyphenyl)-3-(thiophen-3-yl)prop-1-en-3-one, C15H14O2S, (3), and 1-(4-bromophenyl)-3-(thiophen-3-yl)prop-1-en-3-one, C13H9BrOS, (4), are described. The four chalcones have been synthesized by reaction of thiophene-3-carbaldehyde with an acetophenone derivative in an absolute ethanol solution containing potassium hydroxide, and differ in the substituent at the para position of the phenyl ring: -OH for 1, -OCH3 for 2, -OCH2CH3 for 3 and -Br for 4. The thiophene ring in 4 was found to be disordered over two orientations with occupancies 0.702 (4) and 0.298 (4). The configuration about the C=C bond is E. The thiophene and phenyl rings are inclined by 4.73 (12) for 1, 12.36 (11) for 2, 17.44 (11) for 3 and 46.1 (6) and 48.6 (6)° for 4, indicating that the -OH derivative is almost planar and the -Br derivative deviates the most from planarity. However, the substituent has no real influence on the bond distances in the β-unsaturated carbonyl moiety. The molecular packing of 1 features chain formation in the a-axis direction by O - H⋯O contacts. In the case of 2 and 3, the packing is characterized by dimer formation through C - H⋯O interactions. In addition, C - H⋯π(thiophene) interactions in 2 and C - H⋯S(thiophene) interactions in 3 contribute to the three-dimensional architecture. The presence of C - H⋯π(thiophene) contacts in the crystal of 4 results in chain formation in the c-axis direction. The Hirshfeld surface analysis shows that for all four derivatives, the highest contribution to surface contacts arises from contacts in which H atoms are involved.