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Open Access Publications from the University of California

Scholarly Works (8 results)

  • Article
  • Peer Reviewed
UC Santa Barbara Previously Published Works (2019)
A gold-catalyzed glucosylation method using an o-ethynylphenyl β-D-1-thioglucoside as donor is described. The reaction proceeds in a mostly SN2 pathway. A series of α-D-glucosides are obtained in good yields and with up to 19:1 α-selectivity.
    Cover page: Gold-catalyzed synthesis of α-D-glucosides using an o-ethynylphenyl β-D-1-thioglucoside donor
    • Thesis
    • Peer Reviewed
    UC Santa Barbara Electronic Theses and Dissertations (2017)

    Homogeneous gold catalysis has been a very hot topic in recent decades. With its unparalleled π-acidity, cationic gold complex exhibits a strong affinity to alkynes and promotes nucleophilic attack across C-C triple bonds. Such nucleophilic attacks lead to various reactive intermediates that trigger a wide range of cascade reactions, building molecular complexity readily in one step. My doctoral study is focused on the development and application of gold-catalyzed cascade reaction with alkyne substrates. In this dissertation, two methodology studies and two applications of gold-catalyzed cascades will be discussed. Namely: 1) one-pot synthesis of fused pyrroles from ketones and N-alkylhydroxylations via a gold catalysis-triggered cascade; 2) synthesis of polycyclic 2H-pyran-3(6H)-ones via a vinyl cation C(sp3)-H insertion triggered by oxidative gold catalysis; 3) streamlined synthesis of highly potent mitomycin C analogs with gold/platinum-catalyzed cycloisomerization cascade; and 4) gold-catalysis-activated stereoselective glycosylation reaction to construct 1,2-cis glycosyl linkage in glycoconjugates and oligosaccharides.

      Cover page: Gold Catalysis Enabled Cascade Reactions from C-C Triple Bonds
      • Article
      • Peer Reviewed
      UC Santa Barbara Previously Published Works (2014)
      A two-step, one-pot synthesis of fused pyrroles is realized by firstly condensing an N-alkynylhydroxammonium salt with a readily enolizable ketone under mild basic conditions and then subjecting the reaction mixture to a gold catalyst, which triggers a cascade reaction involving a facile initial [3.3]-sigmatropic rearrangement of the gold-catalysis product, that is, an N,O-dialkenylhydroxamine. The reaction provides a facile access to polycyclic pyrroles in moderate to good yields.
        Cover page: One‐Pot Synthesis of Fused Pyrroles through a Key Gold‐Catalysis‐Triggered Cascade
        • Article
        • Peer Reviewed
        UC Santa Barbara Previously Published Works (2020)
        Cyclobutanones are synthetically versatile compounds that often require extensive effort to access. Herein, we report a facile synthesis of cyclobutanones based on the C(sp3 )-H insertion chemistry of oxidatively generated gold carbenes. Various cyclobutanones were obtained in synthetically useful yields from substrates with minimal structural prefunctionalization. This discovery reveals new synthetic utilities of gold-catalyzed oxidative transformations of alkynones.
          Cover page: Non‐Diazo C−H Insertion Approach to Cyclobutanones through Oxidative Gold Catalysis
          • Article
          • Peer Reviewed
          UC Santa Barbara Previously Published Works (2015)
          A newly developed P,N-bidentate ligand enables enantioselective intramolecular cyclopropanation by a reactive α-oxo gold carbene intermediate generated in situ. The ligand design is based on our previously proposed structure (with a well-organized triscoordinated gold center) of the carbene intermediate in the presence of a P,N-bidentate ligand. A C2-symmetric piperidine ring was incorporated in the ligand as the nitrogen-containing moiety. A range of racemic transformations of α-oxo gold carbene intermediates have been developed recently, and this new class of chiral ligands could enable their modification for asymmetric synthesis, as demonstrated in this study.
            Cover page: Enantioselective Oxidative Gold Catalysis Enabled by a Designed Chiral P,N‐Bidentate Ligand
            • Article
            • Peer Reviewed
            UC Santa Barbara Previously Published Works (2021)
            Generally applicable and stereoselective formation of 1,2-cis-glycopyranosidic linkage remains a long sought after yet unmet goal in carbohydrate chemistry. This work advances a strategy to this challenge via stereoinversion at the anomeric position of 1,2-trans glycosyl ester donors. This SN2 glycosylation is enabled under gold catalysis by an oxazole-based directing group optimally tethered to a leaving group and achieved under mild catalytic conditions, in mostly excellent yields, and with good to outstanding selectivities. The strategy is also applied to the synthesis of oligosaccharides.
              Cover page: A “Traceless” Directing Group Enables Catalytic S N 2 Glycosylation toward 1,2-cis-Glycopyranosides
              • Article
              • Peer Reviewed
              UC Santa Barbara Previously Published Works (2021)
              Homogeneous gold catalysis has experienced extraordinary development since the dawn of this millennium. Oxidative gold catalysis is a vibrant and fertile subfield and has over the years delivered a diverse array of versatile synthetic methods of exceptional value to synthetic practices. This review aims to cover this topic in a comprehensive manner. The discussions are organized by the mechanistic aspects of the metal oxidation states and further by the types of oxidants or oxidizing functional groups. Synthetic applications of oxidative gold catalysis are also discussed.
                Cover page: Homogeneous Gold-Catalyzed Oxidation Reactions
                • Article
                • Peer Reviewed
                UC Santa Barbara Previously Published Works (2018)
                A silver-catalyzed glycosylation reaction employing readily accessible and stable glycosyl ynenoates is developed. This reaction is mostly high yielding and exhibits varying levels of stereoinversion at the anomeric position. Compared to established and versatile Yu's gold catalysis, this chemistry features the use of substantially cheaper AgNTf2.
                  Cover page: Silver-catalyzed stereoselective formation of glycosides using glycosyl ynenoates as donors
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