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Browsing by Author "Ferreira, Eric, committee member"

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    Catalytically generated acyl triazoliums as versatile acylating reagents and progress toward the total synthesis of okilactomycin
    (Colorado State University. Libraries, 2013) Wheeler, Philip Andrew Merris, author; Rovis, Tomislav, advisor; Shi, Yian, committee member; Ferreira, Eric, committee member; Shores, Matthew, committee member; Fisk, John D., committee member
    The first chapter of this dissertation describes the development of reactions involving the NHC-catalyzed acylation of carbon and nitrogen nucleophiles. The overall goal of this work was to expand the scope of the NHC-redox reaction manifold and improve its applicability to the synthesis of products that would be useful to the organic chemistry community. An efficient and simple procedure for the preparation of amides from amine hydrochloride salts and α,β-unsaturated aldehydes was developed. This procedure was then applied to the asymmetric synthesis of α-fluoroamides which are valuable building blocks for the preparation of fluorinated compounds that are highly sought after in pharmaceutical, material, and agrichemical applications. The second chapter describes efforts toward the total synthesis of the complex polyketide natural product okilactomycin, enabled by the rhodium-catalyzed desymmetrization of 3,5-dimethylglutaric anhydride developed previously by our group. Progress includes construction of the entire carbon skeleton in two fragments, poised to be unified and elaborated to the natural product by closely precedented steps. This progress demonstrates the potential of the catalytic, enantioselective desymmetrization of anhydrides to build complexity in rapid fashion.
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    Studies concerning platinum-catalyzed 1,6-enyne cycloisomerizations: a unified synthetic approach to the Gelsemium alkaloids
    (Colorado State University. Libraries, 2015) Newcomb, Eric Thomas, author; Kennan, Alan, advisor; Ferreira, Eric, committee member; Prieto, Amy, committee member; McNaughton, Brian, committee member; Akkina, Ramesh, committee member
    The development and application of transition metal-catalyzed enyne cyclization reactions is an ever growing and active area of research in modern organic synthesis. One prolific class of catalysts studied in this broad arena is that of pi-acidic metal complexes. Through further understanding of the fundamental processes of these alkynophilic metal catalysts, we are able to test new transformations in more complex settings. Presented herein are our contributions to the understanding and further implementation of Pt-catalyzed alkyne activation chemistries. In particular, we have developed a chirality transfer protocol to synthesize highly enantioenriched O-tethered cyclopropane-containing compounds. The substrate scope for this process is broad, and the overall transformation is highly stereospecific. Additionally, we further refined a purported mechanistic pathway and extended this chemistry in a number of additional systems. Furthermore, we explored the use of this cycloisomerization chemistry in our synthetic approach to the Gelsemium alkaloids. Specifically, the development of a Pt-catalyzed tandem cycloisomerization/[3,3]-sigmatropic rearrangement allowed us to build a motif shared among a large number of the alkaloids. Following successful implementation of this reaction, we then studied the use of additional late-stage cyclizations to synthesize gelesenicine. Our final two steps, a highly efficient hypervalent iodine-mediated cyclization followed by an iminyl radical cyclization, provided the natural product. Additionally, the synthesis was highly efficient--14 steps--without the use of protecting groups.
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    The application of new methodology to complex molecule synthesis: studies toward the synthesis of pordamacrine A and liphagal
    (Colorado State University. Libraries, 2015) Seizert, Curtis A., author; Kennan, Alan, advisor; Ferreira, Eric, committee member; Chen, Eugene, committee member; Prieto, Amy, committee member; Hansen, Jeffrey, committee member
    The coevolution of organic synthesis and methodology has contributed greatly to the growth of both fields. This has been enabled by the invention of new methods during the prosecution of a synthesis in order to solve an unforeseen problem as well as by the novel application of independently developed methods to complex synthetic settings. Our own studies have encompassed both of these strategies, and we present their results herein. Our initial efforts consisted of synthetic studies towards the complex hexacyclic alkaloid pordamacrine A. This molecule presented many difficulties, and we were forced develop and employ new methods in its synthesis. Ultimately, these studies were stymied by the difficulty of forming the central carbocyclic ring system of this molecule. Among the methods used in the synthesis of pordamacrine A was a variant of a previously reported boron promoted Ireland-Claisen rearrangement. This rearrangement has been reported in very few papers in the literature, and many details of the reaction were undisclosed at the outset of ourstudies. We report here our investigations of the scope and stereochemical features of this rearrangement. Finally, methods based on the use of Pt carbenoids have formed a central element in our group's research focus. We apply here the use of this intermediate to the synthesis of liphagal, a complex tetracyclic compound. Our explorations of Pt-catalyzed cycloaddition reactions based on Pt carbenoids in this study have shed valuable light on the scope of this method. Though our studies culminated in a formal synthesis of an epimer of the natural product, we expect that future work towards liphagal will be able to use this methodology to make the correct diastereomer of liphagal, potentially in enantioenriched form.