Radical intermediates in the homolytic aromatic silylation. An ESR evidence

The cyclohexadienyl radical resulting from the addition of triphenylsilyl radical to the para position of cyanobenzene has been characterized by ESR spectroscopy. Similar adducts were detected with 2-cyano-5-methylthiophene and two isomeric 2-cyano substituted thienothiophenes. The results are consistent with the occurrence of homolytic aromatic silylation.