Multinuclear NMR and ab initio MO studies of 7‐methyl‐7 H ‐pyrrolo [2,3‐ b ]pyridine and related compounds

The contribution of the polarized resonance structures to 7‐methyl‐7 H ‐pyrrolo[2,3,‐ b ]pyridine and 4‐methyl‐4 H ‐pyrrolo [3,2‐ b ] pyridine, which have recently attracted much attention in physico‐chemical studies, was considered based on multinuclear ( 1 H, 13 C and 15 N) NMR spectroscopy and MO calculation. Comparison of the chemical shifts of the compounds with those of other relevant compounds and the effects of concentration and solvents observed by multinuclear NMR suggested that the contribution of the non‐polarized structures to both compounds predominates over that of the polarized structures. This result was also supported by ab initio MO calculations using the 6–31G basis set.