Intramolecular interactions in N‐vinyl‐2‐arylpyrroles and ‐2‐heteroarylpyrroles by ¹H and ¹³C NMR

The introduction of a substituent in the 3‐position of the pyrrole ring in N‐vinyl‐2‐arylpyrroles and ‐2‐heteroarylpyrroles results in an increase in the dihedral angles between the planes of the pyrrole ring and the aryl (or heteroaryl) residue, and a decrease in the dihedral angle between the planes of the pyrrole ring and the vinyl group. Introduction of the substituent in the 5‐position of the pyrrole ring has the opposite effect on these angles. For N‐vinyl‐2‐(2′‐furyl)pyrrole, some spectral data suggest the formation of a CH…O hydrogen bond between the α‐hydrogen atom of the vinyl group and the oxygen atom of the furyl ring. This is in accord with the results of quantum chemical calculations.