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. This Microreview focuses on the regio- and stereoselective preparation of α- and ortho-lithiated oxiranes, aziridines, oxetanes, azetidines, and tetrahydrofurans with special emphasis on factors such as carbene-like character, aggregation, complexation phenomena and dynamics which strongly influence their applications to synthetic chemistry. Recent selected examples extracted from the literature are critically analysed and commented.
Complexation Phenomena and Dynamics at Work in the Lithiation Reactions of Small-Ring Heterocycles: Regio- and Stereoselectivity
CAPRIATI, Vito;LUISI, Renzo
2014-01-01
Abstract
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. This Microreview focuses on the regio- and stereoselective preparation of α- and ortho-lithiated oxiranes, aziridines, oxetanes, azetidines, and tetrahydrofurans with special emphasis on factors such as carbene-like character, aggregation, complexation phenomena and dynamics which strongly influence their applications to synthetic chemistry. Recent selected examples extracted from the literature are critically analysed and commented.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.