Allenyl‐β‐lactams: versatile scaffolds for the synthesis of heterocycles

The hybrid allenic β‐lactam moiety represents an excellent building block for carbo‐ and heterocyclization reactions, affording a large number of cyclic structures containing different sized skeletons in a single step. This strategy has been studied under thermal and radical‐induced conditions. More recently, the use of transition‐metal catalysis has been introduced as an alternative that relies on the activation of the allenic component. On the other hand, the intramolecular version has attracted much attention as a strategy for the synthesis of bi‐ and tricyclic compounds in a regio‐ and stereoselective manner. This overview focuses on the most recently developed cyclizations on 2‐azetidinone‐tethered allenes along with remarkable early works accounting for the mechanism, as well as for the regio‐ and diastereoselectivities of the cyclizations. DOI 10.1002/tcr.201100011