Synthesis and NMR spectra of [¹⁵N]indole

A method was developed for the synthesis of selectively labeled [N-15]indole, allowing to obtain the target product with high chemical and isotopic purity. One-dimensional and two-dimensional H-1, C-13, and N-15 NMR spectra were examined. The chemical shifts of H-1, C-13, and N-15 nuclei were determined, as well as the spin-spin coupling constants of N-15 nucleus and the isotopic chemical shifts of C-13 nuclei for [N-15]indole in CD3CN solution, caused by the replacement of N-14 nucleus with a N-15 nucleus. It was demonstrated that isotopic shifts of this type can provide important structural information. The NMR data set obtained in the current work can serve as an important reference point for establishing the structures of new aromatic heterocycles.