Synthesis and Conformational Analysis of <i>N</i>-Aromatic Acetamides Bearing Thiophene: Effect of Intramolecular Chalcogen–Chalcogen Interaction on Amide Conformational Stability
The conformations of aromatic amides bearing an N-(2-thienyl) or N-(3-thienyl) group were investigated in solution and in the crystal state. NMR spectral data indicate that the conformationalpreferences of these amides in solution are dependent not only on the relative π-electron densities of the N-aromatic moieties, but also on the three-dimensional relationship between carbonyl oxygen and the N-aromatic
The cis-trans conformational equilibrium of amides is of interest because it can be used to control functional activity. Here, we designed and synthesized a series of N-(3-thienyl)amides in order to study the factors affecting their conformational equilibrium. NMR studies showed that the major conformer of N-methyl-N-(3-thienyl)amide in solution is the E-form (cis form), as is the case for N-methylacetamide