β‐Lactams as Formal Dipoles through Amide‐Bond Activation

Abstract Activation of β‐lactams can be achieved by simple Lewis‐base catalysis to trigger an unprecedented reaction based on the formal dipolar behaviour of a strained amide bond. A new synthetic route for 1,3‐oxazinan‐6‐ones is presented by reaction of β‐lactams with ethylglyoxylate, which after methodological optimizations identified 4‐pyrrolidinopyridine as the catalyst of choice in aprotic polar solvents. Mechanistic details are also discussed in light of the intrinsic limitations identified for this transformation.