Ring-Rearrangement Metathesis of Nitroso Diels-Alder Cycloadducts

Strained nitroso Diels–Alder bicyclo[2.2.1] or [2.2.2] adducts functionalized with alkene side chains of diverse length undergo a ring‐rearrangement metathesis process with external alkenes and Grubbs II or Hoveyda–Grubbs II ruthenium catalysts, under microwave irradiation or classical heating, to deliver cis‐fused bicycles of various ring sizes, which contain a NO bond. These scaffolds are of synthetic relevance for the generation of molecular diversity and to the total synthesis of alkaloids. The observation of unexpected reactions, such as epimerization or one‐carbon homologation of the alkene side chain, is also reported. From one bicycle to another: Nitroso Diels–Alder (NDA) bicycloadducts have been converted into valuable fused bicycles that contain NO bonds by using Grubbs or Hoveyda ruthenium carbene catalysts, through a ring‐rearrangement metathesis (RRM) process (see scheme). These scaffolds are of synthetic relevance for the generation of molecular diversity and for the total synthesis of alkaloids.