Nucleophilic addition to diene and arene-metal complexes

Abstract

Attachment of a M(CO)3 unit to a diene (M = Fe) or an arene (M = Cr) induces a strong polarizability in the carbon pi bond systems. Nucleophilic addition occurs to give anionic intermediates which can be manipulated into useful organic products. A series of examples with ŋ4-(1, 3-cyclohexadiene)Fe(C0)3 shows that reactive anions are needed to obtain successful addition and then protonation leads to monosubstituted cyclohexenes. Alternatively, CO insertion can be induced which allows formation of 1, 4-disubstituted cyclohexenes. With arene-Cr(CO)3 complexes, addition to the ring is strongly directed meta to resonance electron donor substituents. This selectivity is the basis for three natural product syntheses, of acorenone, aklavinone, and frenolicin. Special selectivity in additions to ŋ-indole-Cr(CO)3 opens a new approach to the ergot alkaloids. © 1981 IUPAC