Superelectrophilic Intermediates in the Synthesis of Novel Indenole Derivatives via 1,5-Cyclization Reactions of 5-Aryl-1-azapenta-1,4-dien-3-ones - Ghavtadze, Nugzar; Fröhlich, Roland; Bergander, Klaus; Würthwein, Ernst-Ulrich (Synthesis, 2008)