Palladium-Catalyzed Pathways to Aryl-Substituted Indenes: Efficient Synthesis of Ligands and the Respective ansa-Zirconocenes

Substituted 4-/7-halo-1H-indenes and 5-methyl-3-bromo-4-/6H-cyclopenta[b]thiophenes were shown to be convenient starting materials for Suzuki−Miyaura, Negishi, and Murahashi protocols to give the corresponding aryl-subsituted indenes and cyclopenta[b]thiophenes of importance for further synthesis of ansa-metallocenes. Alternatively, (2-methyl-1H-inden-4-yl)boronic acid and (1-methoxy-2-methyl-2,3-dihydro-1H-inden-4-yl)boronic acid as well as the respective organozinc and -magnesium reagents can be used for synthesizing aryl-subsituted indenes via the Pd-catalyzed reactions with aryl halides. These synthetic methods were shown to have a very broad scope to afford libraries of aryl-substituted indenes. Finally, synthesis and structure characterization of several representative chiral ansa-zirconocenes, potentially useful as components of highly active and stereoselective olefin polymerization catalysts, have been performed.