Superacid promoted synthetic transformations and the development of new solid supported Brønsted acids

UnrestrictedThe following dissertation describes the development of several new transformations by the application of a wide range of superacid catalysts and reagent systems for many potential synthetic reactions. The synthesis of some new and novel solid Brønsted acids and their applications in a number of classical organic reactions are also reported in detail. In Chapter 1, a brief overview and history of acids and superacids are given including their different forms and classifications. The strengths of acids and the acidity function are also briefly highlighted along with the importance and application of superacids in organic reactions. Finally, the properties of solid acids and their recent emergence as eco-friendly catalytic alternatives are outlined.; The discussion of new superacid-assisted reactions begins with Chapter 2 in which the triflic acid catalyzed Friedel-Crafts alkylation of aromatics with mono and bis(trifluoromethyl)oxiranes is detailed. Ring opening reactions of these substrates afforded fluorinated β-phenylethanols in excellent yields. The regioselectivity of oxirane ring opening and subsequent Friedel-Crafts alkylation were found to depend upon electronic and steric contributions from the substituents in the oxirane ring which were further explored through DFT studies. Chapter 3 expounds the Nafion-H® catalyzed synthesis of trifluoromethyl imines from benzylamine derivatives and trifluoromethylated ketones. The formation of fluorinated benzaldimines occurs primarily by a previously unreported, acid-catalyzed 1, 3-hydrogen shift. Fluorinated benzaldimines may subsequently be converted to pharmaceutically important α-trifluoromethylated amines.; Chapter 4 summarizes the triflic acid catalyzed sulfonation and alkyl-sulfonation of proton exchange membranes and new synthetic pathways to substituted diarylsulfones and thiochroman dioxides. These reactions are considered new examples of direct Friedel-Crafts cycli-alkyl-sulfonation. Reactions between Polyvinylidene Fluoride – Polystyrene (PVDF-PS) and various reagents, under superacidic conditions, lead to polymeric sulfonic acids while reactions with monomeric aromatics under similar conditions lead to diaryl sulfones or thiochroman dioxides.; Chapter 5 describes the synthesis of polymer-bound Brønsted acids and their use as convenient alternatives to liquid acids. Nitric acid and sulfuric acids have been combined, both individually and as a mixture, with poly(4-vinyl pyridine). The new solid acid systems have been used to nitrate several substituted arenes and proved to be quite effective nitrating agents.; In, Chapter 6, the complexes formed between hydrogen peroxide (H2O2) and poly(N-vinyl pyrrolidone) (PVD) or poly(4-vinyl pyridine) (PVP) have been revealed as successful solid H2O2 equivalents. The complexes are used in the selective oxidation of sulfides to sulfoxides and in the synthesis of gem-diperoxides from ketones. The complexes proved to be convenient, safe and tolerant of a variety of substituents.; Finally, Chapter 7 discusses the use of (aminomethyl)polystyrene as an efficient reservoir for anhydrous HF as the polymer forms ionic solid HF complexes with varying amounts of anhydrous HF. The complexes can be used as a catalyst for isobutylene alkylation as well as a convenient fluoride source for the fluorination of alcohols. Interestingly, treatment of 1-adamantanemethanol with the reagent results in its unexpected ring expansion to homoadamantane involving carbocationic intermediates