The cobalt-mediated [2+2+2] cycloaddition of α,ω-diynes to the 2,3-double bond of indole

Article abstract of DOI:10.1055/s-1994-25696

The reaction of acetyl or phenylsulfonylindole with α,ω-diynes and CpCo(C₂H₄)₂ yields CpCo-complexed dihydrocarbazoles. 1-Trimethylsilyl-1,6-heptadiyne gives an adduct in which the silyl moiety is distal to the phenylsulfonamide. 1-Trimethylsilyl-1,7-octadiyne results in an unusual diene complex resulting from C-H activation at C-2 of the indole. The behavior of a number of terminally substituted 4-aza, 1,7-octadiynes to the reaction is investigated. The oxidation of one dihydrocarbazole complex with triphenylcarbenium hexafluorophosphate or with Fe(NO₃)₃ furnishes an η⁵-cyclohexadienyl cobalt complex and its subsequent conversion into substituted diene complexes or to the demetallated carbazole is discussed.