Supporting-Electrolyte-Free Anodic Oxidation of Oxamic Acids into Isocyanates: An Expedient Way to Access Ureas, Carbamates, and Thiocarbamates

    • Alessia Pettia
    • Corentin Fagnana
    • Carlo G. W. van Melisa
    • Nour Tanbouzab
    • Anthony D. Garciaa
    • Andrea Mastrodonatoa
    • Matthew C. Leecha
    • Iain C. A. Goodalla
    • Adrian P. Dobbsa
    • Thierry Ollevierb
    • Kevin Lam*a
    • aSchool of Science, University of Greenwich, Chatham Maritime, Chatham, Kent ME4 4TB, U.K.
    • bDépartement de Chimie, Université Laval, 1045 avenue de la Médecine, Québec, QC G1V 0A6, Canada

    We report a new electrochemical supporting-electrolyte-free method for synthesizing ureas, carbamates, and thiocarbamates via the oxidation of oxamic acids. This simple, practical, and phosgene-free route includes the generation of an isocyanate intermediate in situ via anodic decarboxylation of an oxamic acid in the presence of an organic base, followed by the one-pot addition of suitable nucleophiles to afford the corresponding ureas, carbamates, and thiocarbamates. This procedure is applicable to different amines, alcohols, and thiols. Furthermore, when single-pass continuous electrochemical flow conditions were used and this reaction was run in a carbon graphite Cgr/Cgr flow cell, urea compounds could be obtained in high yields within a residence time of 6 min, unlocking access to substrates that were inaccessible under batch conditions while being easily scalable.

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