Complexation Phenomena and Dynamics at Work in the Lithiation Reactions of Small‐Ring Heterocycles: Regio‐ and Stereoselectivity

This Microreview focuses on the regio‐ and stereoselective lithiation of small‐ring heterocycles such as aryl‐substituted oxiranes, aziridines, azetidines, oxetanes, and tetrahydrofurans highlighting some useful selected synthetic applications extracted from recent literature. It will be shown, in particular, that regio‐ and stereoselectivity and the configurational stability of the above lithiated species are controlled by a subtle interplay of factors. Aggregation, complexation phenomena, dynamics at the heteroatom of the heterocyclic ring, substitution in both the aryl and the heterocyclic ring, solvent polarity, temperature, and ligands play a crucial role. The ability of the afore‐mentioned heterocycles as important directed metalation groups for the arene ortho ‐functionalization is also discussed as well as the carbene‐like nature exhibited by some lithiated epoxides and aziridines.