Metal reagents in organic reactions. Part-VI. Oxidation of indoles with thallium(III) acetate

The action of thallium(lll) acetate on a number of indoles, differently sub stituted in the 2- and 3-positions, has been investigated. Monomeric and 'd imeric' oxidation products are obtained; the structures of the products dep end on the substituents present in the substrate. A novel oxidative dimeris ation of 2,3-disubstituted indoles to indolo[3.2-b]carbazoles is observed, The generation of the products could be rationalised by the initial formati on of an unstable, non-isolable 3-thallated-indolenine derivative.