Browsing by Subject "Palladium"
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Item Development of Aryl Decarboxylative Functionalization Reactions(2021-05) Daley, RyanNew synthetic methods are needed to address the tremendous environmental costs associated with fine chemical production. Towards this goal, my graduate research has focused on designing and developing new decarboxylative cross-coupling methods. These reactions replace high energy, unstable, and expensive organometallic nucleophiles with low energy and readily available (hetero)aryl carboxylic acids. First, I reported an efficient palladium catalyzed salt-free decarboxylative allylation of allylic carbonates, which was designed to generate base in-situ. Next, I advanced a method for the decarboxylative cross-coupling of inexpensive aryl chlorides. The mechanism of this transformation was investigated and gave insights that enabled an increase in catalyst performance. More recently, I developed the first gold catalyzed decarboxylative cross-coupling of aryl iodides. This reaction overcame limitations associated both with decarboxylative couplings and reactions involving redox events at gold. I then investigated the mechanism this reaction with the goal of surmounting the current limitations of this promising technology.Item Development of new reaction methodologies using palladium catalysts(2014-01) Rondla, Naveen ReddyChapter 1: This chapter provides a brief review of the chemistry of metal catalyzed C-C sigma-bond activation reactions. Literature examples for a variety of methods to activate C-C sigma-bonds and their limitations are discussed in detail. Introduction to C-CN sigma-bond reaction and its advantages over the typical C-C sigma-bond activation reactions are discussed with literature examples. Motivation for the current work is also presented.Chapter 2: Presented herein development of new reaction methodology, intramolecular cyanoesterification of alkynes to synthesize highly functionalized butenolides. The reaction proceeds with commonly used palladium catalyst (Pd(PPh3)4) under microwave conditions in five minutes. The reaction tolerates wide variety of substrates and corresponding results are presented. Plausible mechanistic hypothesis is also discussed. Chapter 3: Presented herein new methodology for intramolecular cyanoacylation of alkenes to synthesize highly functionalized indanones . The major challenge of decarbonylation has been overcome using iminonitriles. The reaction proceeds in the presence of commonly used palladium catalyst (Pd(PPh3)4) and very common Lewis acid ZnCl2. The reaction tolerates wide variety of substrates and corresponding results are presented. Results of mechanistic study of the reaction and plausible mechanism are also presented.Chapter 4: Presented herein our attempt towards development of intramolecular azidocyanation of alkenes using carbamoyl azides. Interestingly instead of azidoacylation product, 2-quinazolinone was isolated by the loss of CH2 and N2. Future work on optimization and applications of this interesting reaction are discussed.Item Innate C-H functionalization of cyclic enaminones(2013-08) Yu, YiyunCyclic enaminones are versatile precursors for the synthesis of alkaloids and nitrogen-containing bioactive compounds. The development of efficient functionalization methods is vital to their synthetic utility. C-H functionalization is a tool to efficiently construct C-C bonds with high atom-economy, and to reduced waste. The work in this dissertation is directed towards the development of efficient and selective C-H functionalization methods for cyclic enaminones.Chapter 1 serves as an introduction to cyclic enaminone chemistry. The synthesis and reactivity of cyclic enaminones, including applications in total synthesis, are summarized. In particular, our recent developments regarding enaminone chemistry are highlighted. Chapter 2 surveys recent advances in Pd-catalyzed C-H functionalization at sp2 carbons. The highlights and problems for C-H functionalization are discussed in detail.Chapter 3 describes a regioselective C-H arylation of cyclic enaminones with aryl iodides. The wide availability of aryl iodides allowed rapid access to 3-arylpiperidines. Chapter 4 expands the reaction scope of cyclic enaminones and presents a unique dehydrogenative alkenylation. This pioneering work is among the early examples of a C-H cross-coupling reaction between alkenes. A variety of cyclic enaminones and alkenes were employed. A mechanistic study of the C-H palladation is also included.Chapter 5 focuses on the synthesis of 5-alkenyluracil scaffolds of medicinal importance. A practical, high-yielding dehydrogenative alkenylation method is presented. The generality of this new method shows a significant improvement over past syntheses.Chapter 6 explores the synthetic utility of alkenylated cyclic enaminones. A superior dehydrogenative alkenylation reaction was discovered using a biomimetic approach. A tandem reaction was found serendipitously that led to a novel synthesis of chalcones.Chapter 7 documents progress concerning the C-H trifluoromethylation of cyclic enaminones. Existing protocols were examined and a palladium-catalyzed protocol was pursued. Remarkably, it was discovered that a metal-free protocol was similarly effective.Our efforts have afforded practical means to functionalize cyclic enaminones. These protocols will undoubtedly increase the synthetic value of cyclic enaminones.