Reactivity of Carbamoyl Radicals. A New, General, Convenient Free-Radical Synthesis of Isocyanates from Monoamides of Oxalic Acid

A new, general, simple synthesis of isocyanates was developed by oxidation of monoamides of oxalic acid with peroxydisulfate catalyzed by Ag and Cu salts. The reaction was carried out in a two-phase system (water and an organic solvent), and it is suitable also for practical applications, due to the simple experimental conditions and the inexpensive as well as nontoxic reagents. The first example of homolytic intramolecular aromatic carbamoylation is also reported.