Sulfanyl radical mediated cyclization of aminyl radicals

1-(2-Aminophenyl)pent-1-yne 1 reacted with benzenethiol at 150 OC under radical conditions to give the thiol/alkyne adduct 2, the benzothiophene 4 and the indole 5. Reaction of 1 with benzenesulfanyl radicals produced from diphenyl disulfide in the absence of hydrogen donors gave only the indole 5 in high yields. Formation of indole 5 was explained in terms of sulfanyl radical mediated aminyl radical cyclization onto the alkyne triple bond. (C) 1998 Elsevier Science Ltd. All rights reserved.