Conformational Stereochemistry of the HERON Amide, N-Methoxy-N-dimethylaminoformamide: A Theoretical Study

The stereochemistry and energetics of conformational interconversions of the bisheteroatom-substituted (HERON) amide, N -methoxy- N -dimethylaminoformamide 3, have been investigated by ab initio methods at the B3LYP/6-31G* level. Four diastereomeric minima and 17 transition structures for conformational interchange were located. Ranges for barriers, in kJ mol - 1, are as follows: N − CO rotation, 53−60; N − N rotation, 51−60; N − O rotation, 27−50; amino N inversion, 19−27. The factors determining the structural details and barrier heights, namely, acyl conjugation, substituent electronegativity, four-electron repulsions, and anomeric effects, are discussed.