Utilization of Superelectrophiles in Organic Synthesis

This dissertation describes the use of triflic acid as a catalyst in organic synthesis. The first chapter is an introduction of reaction classes, reactive intermediate, and superacids.Chapter 2 discusses a series of compounds have been prepared by the Fischer indole synthesis and Friedel–Crafts reactions, using a single acid catalyst in a one-pot conversion. The reactions have worked best with pyridyl-substituted hydrazones/indoles. Chlorination and bromination products are formed in good yields and high regioselectivities. Acylation products have also been prepared by the two-stage reaction. In the case of alkylation, the expected alkyl-substituted indoles are obtained however they are accompanied by over-alkylation products.In chapter 3, Diels−Alder reactions have been accomplished with ethylene as the dienophile through the use of inverseelectron demand Diels−Alder chemistry. As a key aspect of the chemistry, the dienes are part of tri- or dicationic superelectrophilic systems. Theoretical calculations reveal that the highly charged superelectrophiles possess exceptionally low lying LUMOs, and this facilitates the cycloaddition chemistry with ethylene. The chemistry has beenused to prepare a series of tetrahydroquinoline products. This represents the first application of superelectrophilic activation in a cycloaddition reaction and a new method of utilizing ethylene as a C2 building block.In chapter 4, heterocyclic imines provide biaryl products by a two-step transformation. The first transformation involves a Diels–Alder reaction with a multiply protonated imine to give a tetrahydroquinoline product, whereas the second step involves oxidation with elemental sulfur at 260°C.In chapter 5, a series of heterocyclic enones is prepared for heterocyclic indanones synthesis through superelectrophilic Nazarov cyclization. Kinetic studiesrevealsuperelectrophiles enhanced the reaction rate by two folds. A series of cinnamic acid derivatives were used to synthesize substituted indanone in one pot reaction.Chapter 6, a series of quinoline derivatives have been synthesized in superacid promoted reactions. The key step of this procedure involves aromatization by the elimination of hydrochloric acid or benzene- occurring through ipso-protonation at the phenyl group. The chemistry utilizes rapidly available anilines and α, β unsaturated carbonyl compounds.