Nucleophilic Nitrenoids Through π-Acid Catalysis: Providing a Common Basis for Rapid Access into Diverse Nitrogen Heterocycles

Nitrogen heterocycles are some of the most important and sought-after structural motifs in synthetic chemistry. General methods that can be applied towards a structurally diverse range of different scaffolds are rare. This Focus Review discusses an emerging area with the field of pi-acid catalysis based on the activation of carbon-carbon triple bonds in conjunction with nucleophilic nitrenoids. The resulting approach provides ready access into alpha-imino metal carbene reactivity patterns that can be employed in a number of quenching processes to realize a variety of powerful new transformations. The resulting methods are characterized by high efficiency, simple and straightforward reaction set ups, mild conditions, and excellent functional group tolerance. In this Focus Review the different nucleophilic nitrenoid types are explored showing how they can be used across a range of (poly)cyclization and formal cycloaddition processes to provide an alternative and direct disconnection pathway in the generation of N-heterocyclic motifs.