Fluorinative Rearrangement of Vinyl Diazo Compounds Enabled by a New Reactivity Mode of Cyclopropanediazonium Ions.

Although selective transformations of aromatic and purely aliphatic diazonium ions are well-established, the reactivity of the unique cyclopropanediazonium (CPD) ions remains largely unexplored owing to their intrinsic instability. Herein, we report a new reaction mode of CPD ions mediated by hypervalent iodine reagents. The reaction enables a fluorinative 1,2-diazo function migration of vinyl diazo compounds to afford synthetically useful but previously unavailable β,β-difluorinated diazoester products. This transformation exhibits high efficiency, broad substrate scope, facile scalability, and complete chemo- and regioselectivity, alongside versatile downstream applications. Both control experiments and detailed DFT calculations suggest the formation of a key CPD ion intermediate that undergoes an unprecedented ring-opening rearrangement of such species to furnish the product. Despite the pronounced complexity of the reaction pathway, which requires precise selectivity control at nearly every step, comprehensive computational analysis of a range of possible transition states elucidates the unusual reactivity and underlying origin of the observed selectivity.