In situ generated tris(p-bromophenyl)amine radical cation promoted electron transfer reaction of cyclopropyl silyl ethers

Tris(p-bromophenyl)aminium hexachloroantimonate and perchlorate were utilized to promote the oxidative ring-opening reaction of cyclopropyl silyl ethers giving ring-expanded ketones. Exploration of salt quantity effect on the reaction allowed us to hypothesize that amine radical cation is regenerated through the oxidation of neutral amine by hexachloroantimonate anion. Based on this hypothesis, amine radical cation was initially generated by the treatment of parent amine with either antimony pentachloride or the mixture of silver perchlorate and molecular iodine, and subsequently reacted with same substrates. The in situ generated amine radical cation was found to promote the reaction, and the expected products were obtained in better yields than via use of the corresponding salt reagents.