1. Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
2. Institute of Organic Chemistry, RWTH Aachen, Landoltweg 1, 52074 Aachen, Germany
3. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States