1. Department of Organic Chemistry, Faculty of Sciences, Campus Fuentenueva s/n, University of Granada, E-18071 Granada, Spain, Department of Organic Chemistry, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain, and Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 Tarragona, Spain aechavarren@iciq.es; jmcuerva@ugr.es