NMR studies of indoles and their N‐carboalkoxy derivatives

The 13 C NMR assignment of indoles and 5‐methoxyindoles substituted at position 3, and some of their N ‐carboalkoxy derivatives, was achieved from one‐ and two‐dimensional NMR experiments. Substituent chemical shifts and 1 J (CH) values were evaluated. The dynamic processes of N ‐carboalkoxyindoles and N ‐carboalkoxyindoline observed by high‐field 1 H NMR show the existence of two preferred rotamers around the carbamate NC(O)OR bond, which was interpreted in terms of frequency/field strength‐dependent phenomena.