1. Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC) and Biomolecular Architecture, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium, and Christian Doppler Laboratory for Microwave Chemistry, Institute of Chemistry, Karl-Franzens-University Graz, Heinrichstrasse 28, A-8010 Graz, Austria