1. a Departmental Institute of Chemistry , Industrial Chemistry of the University , Viale Andrea Doria 6, Catania , 95125 , Italy
2. b Cattedra di Chimica Organica, Faculty of Pharmacy , University of Bologna , Via Zanolini 3, Bologna , 40126 , Italy
3. c Institute of Organic Chemistry of the University , Via Archirafi 20, Palermo , 90123 , Italy