Crystal structures of (1E,4E)-1,5-bis(5-bromothiophen-2-yl)-2,4-dimethylpenta-1,4-dien-3-one and (E)-4-(5-bromothiophen-2-yl)-1,3-diphenylbut-3-en-2-one

Abstract

The title compounds, C15H12Br2OS2, (I), and C20H15BrOS, (II), were synthesized by employing Claisen–Schmidt condensation of pentan-3-one and dibenzylacetone with 5-bromothiophene-2-carbaldehyde in the presence of methanolic KOH. Even though 1:2 products were expected in both of the reactions, 1:2 and 1:1 products were obtained as (I) and (II), respectively. In (I), the two methyl groups are trans to each other, 29.5 (7) and 28.7 (7)° away from the central carbonyl bond between them, whereas the two phenyl rings of dibenzylacetone subtend a dihedral angle of 53.09 (18)°. In the crystal of (I), C—H...O hydrogen bonds define molecular chains along c. A second type of molecular chain is formed along b by means of C—Br...π interactions. These two families of molecular chains are stacked by π–π interactions, forming a three-dimensional supramolecular architecture. In (II), similar C—H...O hydrogen bonds as in (I) define inversion dimers, whilst C—H....π interactions build a staircase structure along the a axis.

Keywords

• crystal structure
• Claisen–Schmidt
• 5-bromothiophene-2-carbaldehyde
• pentan-3-one
• dibenzylacetone