Attached Nitrogen Test by 13 C- 14 N Solid-State NMR Spectroscopy for the Structure Determination of Heterocyclic Isomers.

Differentiation of heterocyclic isomers by solution 1 H, 13 C, and 15 N NMR spectroscopy is often challenging due to similarities in their spectroscopic signatures. Here, 13 C{ 14 N} solid-state NMR spectroscopy experiments are shown to operate as an "attached nitrogen test", where heterocyclic isomers are easy to distinguish based on one-dimensional nitrogen-filtered 13 C solid-state NMR. We anticipate that these NMR experiments will facilitate the assignment of heterocyclic isomers during synthesis and natural product discovery.