Synthesis and Rearrangement of N-Organyloxy β-Lactams Derived from a (4+2)/(3+2) Sequential Cycloaddition Reaction Involving Enol Ethers and Nitro Alkenes

The synthesis of N‐organyloxy β‐lactams 2 by treatment of nitroso acetals 1 with a base is discussed. Based on the formation of a by‐product, a mechanism for the rearrangement to N‐organyloxy β‐lactams is proposed. This mechanism is supported by trapping of the intermediate acyl nitro compound 8 with dimethylamine. Furthermore, it was discovered that upon more forcing basic conditions these N‐organyloxy β‐lactams can rearrange further to 3‐organyloxy β‐lactams. By using a series of structurally diverse N‐organyloxy β‐lactams the generality of this novel rearrangement is demonstrated. A mechanism for the conversion of N‐organyloxy β‐lactams to 3‐organyloxy β‐lactams is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)