Metz, Alison E

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  • Publication
    Part I: Synthesis and Chemistry of 2-Aryl-2-Nitroacetates Part II: Development of Anion-Binding Catalysts Part III: Analysis of an Axial Chiral Tetrachlorinated Bisbenzo[a]phenazine
    (2015-01-01) Metz, Alison E
    PART I. There are few reports on the synthesis of 2-aryl-2-nitroacetates, highlighting a need for development in this area. This section describes a high-throughput experimentation (HTE) approach to discover suitable conditions for the coupling of aryl bromides and α-nitroacetates to generate 2-aryl-2-nitroacetates. The best reaction conditions are 2.5 mol % Pd2dba3•CHCl3, 10 mol % t-BuXPhos, 1.2 equiv CsHCO3 in toluene at 75 °C, which afford products in isolated yields of 52–96%. 2-Aryl-2-nitroacetates are central precursors to other small molecules making them valuable building blocks in synthesis. Efficient methods were developed for the conversion of 2-aryl-2-nitroacetates to several product classes that are difficult to make: aryl nitromethanes (76–98% yield), α-keto esters (51–86% yield), and α-aryl α-amino acids (63–85% yield). PART II. Small molecule organocatalytic anion-binding chemistry is in its early stages of development in the organic laboratory, and research in this field is important for its advancement. This section describes synthesis of a new class of anion-binding catalysts focused on a xanthene scaffold. Over twenty potential catalysts were made and include three types: unsymmetrical catalysts, C2-symmetrical catalysts, and bifunctional catalysts. These compounds are better at promoting the Pictet-Spengler-type reaction previously reported by Jacobsen. Because of this fact the cyclization of 3- and 2-substituted furans into N-acyliminium ions was investigated. The top catalyst for 2-substituted furans is a bisamide xanthene compound (60% conversion), and the top catalyst for 3-substituted furans is a thiourea-amide xanthene compound (42% conversion, 24% ee). PART III. The discovery of new materials is an exciting and important field of organic synthesis. A tetrachlorinated bisbenzo[a]phenazine was accessed in seven steps and 14% overall yield (99% ee). It has unique chromic properties that justify its application in functional materials. The color-changing transitions and the corresponding solid phases were studied using single crystal x-ray diffraction, powder x-ray diffraction, photo-image processing, and differential scanning calorimetry. These properties arise from two polymorphs and the ability of the phenazine to form weak OH•••Cl interactions.