Tony C. T. Chang

Cationic enol ether-iron complexes as vinyl cation equivalents. Synthesis of protolichesterinic ester

The reaction of lithium enolates derived from β-keto esters with complex cation 4 provides a facile route to 3,4-disubstituted α-methylene-γ-lactones.

SYNTHETIC APPLICATIONS OF THE CHEMISTRY OF DICARBONYL CYCLOPENTADIENYLIRON COMPLEXES

Abstract The use of Fp(vinyl ether) cations [Fp≡C 5 H 5 Fe(CO) 2 ] as vinyl cation equivalents is described. Carbon nucleophiles generally add nonregiospecifically to the activated double bond of Fp(olefin) cations. However, nucleophilic addition to vinyl ether complexes ( 1 ) is highly regiospecific. The products are (β-alkoxyalkyl)Fp complexes ( 2 ) which are in turn readily transformed to Fp(olefin) complexes ( 3 ) by brief treatment with acid at low temperatures. Release of the free vinyl group from 3 is simply achieved by brief exposure to iodide, or bromide. The stereochemistry of these reactions and several applications of the above sequence are illustrated.