Date of Award
Chemistry and Biochemistry
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The reaction between $\gamma$-acetoxy-$\alpha,\beta$-unsaturated esters with diiron nonacarbonyl produces the $\eta\sp2$-iron tetracarbonyl complexes. Addition of a Lewis acid, such as boron trifluoride etherate, produces $\eta\sp3$-iron allyl cationic complexes. These complexes react with silyl enol ethers and silyl ketene acetals to afford the addition products. The regiochemistry is such that the addition occurs at the terminus of the allyl fragment remote from the ester function to produce $\gamma$ substitution products. The geometric stability of the iron allyl cation allows the stereochemical integrity of the double bond to remain intact during the course of the reaction. Cyclic silyl ketene acetals and silyl enol ethers provide difunctionalized cyclic products containing a quaternary centre. These products are precursors to a variety of spirocyclic ring systems. Three types of spirocyclizations were performed with the iron allyl addition products. Attempts at cyclizing the alkene failed to produce any product cleanly, so the compounds were first hydrogenated. The Dieckmann and the acyloin condensations produced the corresponding spirocycles. Cyclization by metal halogen exchange also formed a spirocycle in low yield. Further investigation of this reaction and its application to natural product synthesis will be discussed. Source: Masters Abstracts International, Volume: 34-06, page: 2378. Adviser: James R. Green. Thesis (M.Sc.)--University of Windsor (Canada), 1996.
Charlton, Margaret Anne., "The iron mediated (1,5)-homologous Michael reaction as a route to spirocyclic ring systems." (1996). Electronic Theses and Dissertations. 4077.