Investigation of C–H⋯X (X=N, O, S) intramolecular hydrogen bond in 1-vinyl-2-(2′-heteroaryl)pyrroles by ab initio calculations

Abstract The C–H⋯X (X=N, O, S) intramolecular hydrogen bond between the α-hydrogen of the vinyl group and the corresponding heteroatom in the series of 1-vinyl-2-(2′-heteroaryl)pyrroles was examined by ab initio calculations at the B3LYP/6-311(d,p) level. It was shown that the C–H⋯N hydrogen bond is stronger than the C–H⋯O hydrogen bond and the latter is, in turn, stronger than the C–H⋯S hydrogen bond. This conclusion is supported by calculations of 1 H NMR chemical shieldings.