Transition-Metal-Catalyzed Ring Expansion of Diazocarbonylated Cyclic N‑Hydroxylamines: A New Approach to Cyclic Ketonitrones
journal contributionposted on 05.09.2014, 00:00 by Evelyn Lieou Kui, Alice Kanazawa, Jean-François Poisson, Sandrine Py
Novel C-ethoxycarbonyl cyclic ketonitrones are synthesized from the Ag- or Cu-catalyzed ring expansion of β-diazo cyclic hydroxylamines. The latter are themselves easily obtained by the addition of lithiated ethyl diazoacetate onto cyclic nitrones. The regioselective metal-catalyzed rearrangement of β-diazo cyclic hydroxylamines proved highly efficient and resulted in a synthetically useful ring expansion to produce 6- or 7-membered ring functionalized nitrones. The outcome of the two steps, i.e. nucleophilic addition of α-diazoesters to nitrones and ring expansion, is a formal nitrone homologation.