Part A The application of fluorescence resonance energy transfer to reaction discovery Part B The stereodefined synthesis of tetrasubstituted olefins

Abstract

In part A, the development of methodology for enantioselective reaction monitoring using Fluorescence Resonance Energy Transfer (FRET) is described. The syntheses of enantiomeric epoxides bearing different fluorescent donors and a phenol that bore fluorescence acceptor were explored.* Part B describes the stereodefined synthesis of tetrasubstituted olefins. 2-Alkynyl esters were selectively converted to E-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters by exposure to Bu4NI in refluxing dichloroethane. These products were produced cleanly, regio- and stereoselectively, and in high yields. The treatment of the same substrates with ICI produced mixtures of isomers. Mechanistic studies indicated that ICI was the most plausible intermediate and that a Bu4NI-ICI complex was likely responsible for the high selectivity observed in the Bu4NI/DCE system.* The Bu4NI/DCE system was shown to be selective for the chlorination of alkenes. The treatment of the same alkenes with ICI returned a mixture of chlorinated and iodochlorinated products. In addition, the Bu4NI/DCE system was chemoselective in substrates bearing both aromatic and olefinic moieties, reacting at the alkenyl functionality exclusively. Exposure of these substrates to ICI produced a mixture of products.* The halogenated olefins produced in the initial study were employed as olefin templates for the formation of tetrasubstituted olefins. Regioselective and stereospecific palladium-catalyzed cross-coupling reactions were employed to incorporate a wide variety of substituents into the highly congested olefins, affording single isomer products in good yields.* *Please refer to dissertation for diagrams.