CONSTRUCTION OF BRIDGED AND FUSED BICYCLIC SKELETONS VIA INTRAMOLECULAR ADDITION OF NUCLEOPHILES TO (ETA-4-DIENE)FE(CO)3 COMPLEXES BEARING FUNCTIONALIZED SIDE-CHAINS

Abstract: Reaction of lithium diisopropylamide (LDA) with (eta4-1,3-cy clohexadiene)Fe(CO)3 complexes bearing functionalized side chains at C -5, under an atmosphere of carbon monoxide, gives bridged bicyclo[3.2. 1]octene and bicyclo[3.3.1]nonene systems after electrophilic quenchin g, whereas larger rings cannot be obtained in this series. Under the s ame reaction conditions, intramolecular cyclization of acyclic (eta4-1 ,3-butadiene)Fe(CO)3 complexes with functionalized side chains at the terminal position of the diene ligands furnishes fused bicyclo[3.3.0]o ctanone and bicyclo[4.3.0]nonanone derivatives after acid quenching. T he iron-mediated intramolecular nucleophilic addition allows for the d irect stereocontrol of four stereogenic centers of these fused bicycli c skeletons.