Reactions of electron-rich indoles with triflic anhydride

The reaction of electron-rich 3-aryl-substituted 4,6-dimethoxyindoles in the presence of base with triflic anhydride results in biaryl coupling, producing both 2,2′- and 2,7′-biindoles. Further, if acetone is present, the corresponding vinyl triflate is formed and subsequent reaction yields the known indolylpyrroloindoles and dimeric spiroindoles. This is the first reported synthesis of these compounds under basic conditions.