Diazo-Based Construction of Heterocyclic Systems Via a X−H Insertion/Cyclization Cascade

The X−H insertion reaction (X=heteroatom) of diazo compounds has emerged as an eminent and reliant approach for the construction of C−X bonds. By merging X−H insertion with the sequential ring-closing transformations, diverse heterocyclic systems can be obtained in a step-economical manner. In recent years, the X−H insertion/cyclization cascades and one-pot transformations attract more research attention, especially in the area of asymmetric synthesis. Concentrating on the assembly of N,O,S-heterocycles, this Concept elucidates the various combinations of X−H insertion reactions with cyclization via an addition to multiple bonds. The ring-forming strategies reviewed comprise of Michael-type and Conia-ene reactions, aldol condensation, and Mannich reaction.