ELECTRON-TRANSFER REACTIONS - A REINVESTIGATION OF THE CHLORINATION OF 1-METHYL-2-PHENYLINDOLE WITH N-CHLOROBENZOTRIAZOLE - THE ROLE OF OXYGEN AND OXYGENATED SOLVENT

1-Methyl-phenylindole (1, MPI-H) reacts with N-chlorobenzotriazole (2, BT-Cl) to form the corresponding radical cation (MPI-H).+ which itself, or via the indolyl radical (MPI).+, formed by deprotonation of MPI-H.+, reacts with oxygen or a nucleophilic solvent leading to indoxyls 4-7. Cyclic voltammetric studies, as well as the oxidation of MPI-H with BT-Cl carried out in the EPR cavity, show that the radical cation MPI-H.+ dimerizes to give 3,3'-(MPI)2 8 which is transformed into the corresponding radical cation 3,3'-(MPI)2.+ in the reaction medium. The identity of this radical cation has been confirmed by oxidizing 3,3'-(MPI)2 directly. The formation of the radical cations MPI-H.+ and 3,3'-(MPI)2.+ has been monitored by UV-VIS spectroscopy and their decay rate constants measured.