Diastereoselective Synthesis of Nitrogen-Containing Heterobicyclic and -tricyclic Skeletons via Intramolecular Cyclization of (η⁴-diene)Fe(CO)₃ Complexes Bearing Amino Acid Derivatives

Addition of secondary amino acid derivatives to (η⁵-pentadienyl)tricarbonyliron cations gives (η⁴-diene)tricarbonyliron complexes in high yields with amino ester groups at the terminal position of the diene ligands. Treatments of the adducts containing a sarcosine, phenylalanine, or alanine moiety with lithium diisopropylamide (LDA), under an atmosphere of carbon monoxide, furnish fused 3-azabicyclo[3.3.0]octanecarboxylic acid derivatives. Under the same reaction conditions, intramolecular cyclizations of complexes containing a proline or pipecolinic acid derivative at the terminal position of the diene ligands give 6-azatricyclo[6.3.0.0²'⁶]undecane and 7-azatricyclo[7.3.0.0²'⁷]dodecane ring systems, respectively, whereas treatment of the complex containing a nipecotic acid derivative provides a bridged 8-azatricyclo[6.3.1.0²'⁶]dodecanecarboxylic acid derivative.