15 N labeling and analysis of 13 C- 15 N and 1 H- 15 N couplings in studies of the structures and chemical transformations of nitrogen heterocycles.

This review provides a generalization of effective examples of 15 N labeling followed by an analysis of 13 C- 15 N ( J CN ) and 1 H- 15 N ( J HN ) coupling constants in solution as a tool to study the structural aspects and pathways of chemical transformations ( e.g. , rearrangements and ring-chain tautomerisms) in monocyclic and fused nitrogen heterocycles. This approach allows us to significantly expand and supplement the scope of NMR techniques for heterocyclic compounds. Moreover, methods for the incorporation of 15 N atoms into the cores of various N-heterocycles have been collected in this work.