Preparation of Cyclopropanes via Organoiron Methodology

The cyclopropane moiety is found in a wide variety of the natural products, from small amino acid molecules to the structurally intriguing (and synthetically challenging) polycyclopropanes. This is perhaps somewhat surprising, due to the inherent instability associated with simplest of carbocyclic rings. Cyclopropanes are unique in both their bonding and reactivity. In fact it is the sp2-like character of the cyclopropane carbons that ultimately determines their reactivity. Indeed, most reactions associated with alkenes have similar counterparts in cyclopropane chemistry. At the same time, organoiron chemistry is dominated by π-olefin complexes, and it somehow seems intuitive that cyclopropanes might be prepared ( or undesirably destroyed) via stoichiometric transition metal chemistry. Because nucleophilic addition to cationic organoiron complexes is often highly stereoselective, in principle it also ought to be possible to prepare functionalized 3-membered rings in a stereocontrolled fashion. This work details an organoiron approach to the synthesis of cyclopropanes. Chapter 1 deals primarily with the synthesis and reactivity of (bicyclo[5.l.O]octadienyl)iron( l +) cations. The knowledge gained was.used to synthesize CCG-III, a small molecule neurotransmitter. Chapter 2 has a more general methodological focus; the synthesis of functionalized divinylcyclopropanes. These molecules serve as precursors to cycloheptadienes (via a Cope rearrangement)