Synthesis of five-, six-, and seven-membered cyclic isoureas via MHAT/RPC promoted cycloisomerization

This study demonstrates a novel method for synthesizing rare heterocyclic compounds, namely, cyclic isoureas using alkenoic ureas via cobalt-catalyzed metal-catalyzed hydrogen atom transfer/radical polar crossover (MHAT/RPC). This method successfully produces five-membered rings along with the rare six- and seven-membered cyclic isoureas. Density functional theory (DFT) calculations were performed to elucidate the reaction mechanism focusing on cyclization.