Optimization of interactions in crystal packing revealed by crystal structures [ethyl 2-(formylamino)-3-thien-2-yl-2-(thien-2-ylmethyl)propanoate and ethyl 3-(5-bromothien-2-yl)-2-[(5-bromothien-2-yl)methyl]-2-(formylamino)propanoate]

Abstract

The title compounds, C₁₅H₁₄NO₃S₂ (I) and C₁₅H₁₅Br₂NO₃S₂ (II), are derivatives of Aib (α-aminoisobutyric acid) with thiophene rings substituted at the C^α position. The C^α substitution causes the backbone to assume an extended conformation in the crystal structure. N-H and C-H donors share the thiophene ring π system for X-H···π interactions. The packings of the molecules are stabilized by intermolecular N-H···O, C-H···O, C-H···π and C-H···Br hydrogen bonds. Br···O interactions and a weak dihydrogen bond have also been observed in the crystal structure of II. The packing adopted by II has maximized the number of interactions that are possible.