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

This review provides a generalization of effective examples of N labeling followed by an analysis of C-N ( ) and H-N ( ) coupling constants in solution as a tool to study the structural aspects and pathways of chemical transformations (, 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 N atoms into the cores of various N-heterocycles have been collected in this work.