β‐Lactam Synthesis through Diodomethane Addition to Amide Dianions

We present a novel route for the quick and easy synthesis of a broad range of β‐lactams. The synthesis involves a [3+1] cyclization of amide dianions with diiodomethane. In contrast to the seminal work of Hirai et al. from 1979, the reaction proved to be a general and efficient approach towards azetidinones. The ease of the process was confirmed by DFT calculations and its power demonstrated by a diversity‐oriented synthesis of β‐lactams with four points of diversity determined by the choice of Ugi adducts as starting materials. Old dog new tricks: A facile synthesis of a broad range of β‐lactams through [3+1] cyclization of amide dianions with diiodomethane was developed. In contrast to the seminal work of Hirai et al. from 1979, the reaction proved to be a general and efficient approach towards azetidinones. The utility of the process was demonstrated by a diversity‐oriented synthesis of β‐lactams with four points of diversity determined by the choice of Ugi adducts as starting materials.