Reactivity of acyclic (pentadienyl)iron(1+) cations: Synthetic studies directed toward the frondosins

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Natural Products Synthesis via Organoiron Methodology

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Organic and Biomolecular Chemistry

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A short, 4-step route to the scaffold of frondosin A and B is reported. The [1-methoxycarbonyl-5-(2′,5′-dimethoxyphenyl)pentadienyl]Fe(CO)3+ cation was prepared in two steps from (methyl 6-oxo-2,4-hexadienoate)Fe(CO)3. Reaction of this cation with isopropenyl Grignard or cyclohexenyllithium reagents affords (2-alkenyl-5-aryl-1-methoxycarbonyl-3-pentene-1,5-diyl)Fe(CO)3 along with other addition products. Oxidative decomplexation of these (pentenediyl)iron complexes, utilizing CuCl2, affords 6-aryl-3-methoxycarbonyl-1,4-cycloheptadienes via the presumed intermediacy of a cis-divinylcyclopropane.

Document Rights and Citation of Original

Organic & Biomolecular Chemistry, Vol. 9, No. 22 (November 2011): 7742-7747. DOI: 10.1039/C1OB05720K.