Doctor of Philosophy (PhD)
This dissertation focuses on two main projects, global chlorination and enamide functionalization, which both encompass in cationic intermediates. Inspired by the desires to find a new chlorination method, global chlorination project is emphasized in chapter one and chapter two, in which chapter one details various known chlorine-containing natural products, including alkyl chlorides and vinyl chlorides. This chapter also describes the previously known protocols to synthesize alkyl chlorides in the attempts of chlorosulfolipids total syntheses, as well as several known reactions to synthesize vinyl chlorides that are both important functional groups in organic synthesis. Chapter two depicts our novel synthetic reaction methodology to install carbon-chlorine bonds using a mild reaction conditions of triphosgene-pyridine mixture. These conditions were applicable not only in converting stereocomplimentary 1,3-anti and 1,3-syn diols to their corresponding 1,3-anti and 1,3-syn dichlorides, but also 1,3,5-anti and 1,3,5-syn triols to their respective 1,3,5-anti and 1,3,5-syn trichlorides. Further utilization of triphosgene-pyridine mixture is also described in chapter two where ketones were successfully transformed into vinyl chlorides.
Meanwhile, chapter three to chapter five describe the enamide functionalization project, which involves in the formation of 2-amidoallyl cation intermediates. Chapter three explains several known methods to generate both 2-amino and 2-amidoallyl cations and their applicability in mainly cycloaddition reactions. The importance of enamide functional groups and the limited 2-amidoallyl cations exploration encouraged us to discover a new reaction method, especially by using Brønsted acid, and these are detailed in chapter four and chapter five. By using catalytic amount of pyridinium triflate in room temperature, regioselective nucleophilic addition to the a’-position was successfully achieved to produce numerous a,a’-substituted enamides in high yields, as presented in chapter four. Extension of this method using catalytic amount of chiral Brønsted acid is demonstrated in chapter five. In the presence of chiral phosphoric acid in dichloroethane at -10 °C or -5 °C, direct nucleophilic addition was obtained at the b-position to yield the unprecedented a,b-substituted enamides in high yields with excellent regioselectivity and enantioselectivity.
Saputra, Mirza Ardella, "New Synthetic Reactions Towards Global Chlorination and Enamides Functionalization" (2017). LSU Doctoral Dissertations. 4126.