Tricarbonyl[(1−4-η)-2-Methoxy-5-methylenecyclohexa- 1,3-diene]iron as a Synthetic Intermediate:  Sequential Electrophilic and Nucleophilic Additions

Abstract

Tricarbonyl[(1−4-η)-2-methoxy-5-methylenecyclohexa-1,3-diene]iron reacts with electrophiles to give the cyclohexadienylium−Fe(CO)3 cation, which either reacts with nucleophiles to form a new quaternary center or undergoes competitive loss of an acidic α-proton to give a new triene complex. This constitutes a new reaction sequence for the synthesis of 4,4-disubstituted cyclohexen-2-ones with the simultaneous introduction of two functional groups.

Synthesis and Reactivity of (Tricarbonyl)(1-ethoxycarbonyl-2-methylpentadienyl)iron(1+) Cation

“…Where these types of reactions occur with predictable regioselectivity they can be of synthetic utility. For example, (cyclohexadienyl)iron(1+) cations ( 1 ) are known to undergo nuclophilic attack at the terminal dienyl carbon (eq 1) . While it might be anticipated that nucleophilic attack on the corresponding acyclic (pentadienyl)iron(1+) cations should be similar, significant differences in reactivity do exist.…”