The Mechanism of Bu₃SnH‐Mediated Homolytic Aromatic Substitution

The fate of intermediate π radicals is crucial in Bu3SnH-mediated cyclization by homolytic aromatic substitution, for example, of bromo compound 1 via radical 2 to give oxindole 3 (AIBN=azobisisobutyronitrile). The results indicate that the mechanism requires the abstraction of a hydrogen radical from the intermediate π radical by the radical initiator or a product of initiator breakdown, and also that arene solvents are not always the best solvents for radical reactions.