| Generating and reacting cations at the site epsilon- to a carbonyl, or other electron-withdrawing group, is a segment of Umpolung chemistry which has seen little research as it is a synthetic challenge. This is especially true of reactions involving sole epsilon-site reactivity, since often reactivity at the gamma-site competes.;This thesis demonstrates the synthesis of four epsilon-carbonyl cation equivalents and their reaction with nucleophiles. These reactions were facilitated by Lewis acid catalysts and gave sole epsilon-reactivity with fair to excellent yields. Two ester substrates were synthesized in simple, high-yielding reactions while two ketone substrates were more difficult to obtain in significant quantities, but were successfully synthesized. When each of the compounds were reacted with a variety of nucleophiles the greatest results were obtained from aromatic nucleophiles, in yields of up to 92%. A handful of nucleophiles--- those containing Lewis basic components or trimethylsilyl groups--- presented challenges, but after adjusting the Lewis acid catalyst loading or catalyst itself the desired products were obtained in some amount. The ionizations of these substrates, and similar compounds, were also studied by computational methods to show the desired transformations are energetically attainable. |
