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

• Alessia Petti^a
• Corentin Fagnan^a
• Carlo G. W. van Melis^a
• Nour Tanbouza^b
• Anthony D. Garcia^a
• Andrea Mastrodonato^a
• Matthew C. Leech^a
• Iain C. A. Goodall^a
• Adrian P. Dobbs^a
• Thierry Ollevier^b
• 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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