Recent Advances in Lewis Base-Catalyzed, Stereoselective Tandem Aldol b- and g-Lactonizations

Stereoselective methods for the synthesis of β-lactones involving a Lewis base-promoted (nucleophile-promoted) aldol-lactonization manifold have continued to expand since the initial reports of Bormann and Wegler in the late 1960's and later by Wynberg and Staring in the early 1980's.This review will cover these developments including enantioselective versions of these processes.Cinchona alkaloids and various pyridine derivatives have been used most extensively to expand the repertoire of β-lactones accessible by this process.Furthermore, recent advances in the development of a 3 -d 3 -ümpolung pathways using N-heterocyclic carbenes have also enabled access to previously unattainable manifolds for the stereoselective synthesis of both β-and γ-lactones via aldol-lactonization pathways.