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Subject: search.filters.subject.Enantioselective catalysis

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    Asymmetric catalysis via spatially separated chiral and catalytic motifs in multicomponent metal-organic frameworks : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2025-11-18) Petters, Ludwig
    Modern life without catalysis is inconceivable. Asymmetric catalysts are a special type of catalyst that preferentially produce one of two possible enantiomers over the other. The ability to selectively obtain exclusively one of the possible enantiomers is of highest importance for modern synthetic chemistry. To enable the transfer of chiral information from the catalyst to the reaction substrates, asymmetric catalysts must be chiral. In conventional asymmetric catalysts, the catalytic and chiral motifs are held close together within one single molecule. In this work, we break the design limitation of conventional asymmetric catalysts with a strategy we call ‘remote asymmetric induction’ (RAI). In RAI catalysts, the catalytic and chiral motifs are independent of each other in their design and synthesis. To achieve this, we use the multicomponent metal-organic framework MUF-77 (MUF = Massey University Framework). MUF-77 consists of three chemically distinct linkers that each occupy a specific position in the framework without disorder or randomness. To create RAI catalysts, the catalytic and chiral motifs are individually anchored to the different building blocks of MUF-77. By virtue of the MUF-77 structure, the catalytic and chiral motifs are in close proximity to one another in a catalytic pore, which creates an active site. This enables the transfer of chiral information to the reaction participants. Initially the reaction scope of the RAI catalyst was expanded by screening a variety of RAI-MOFs incorporating different catalytic and chiral functionalities across a range of model reactions. A promising catalyst for one model reaction was identified and investigated in depth. Through systematic modification of important reaction variables, the variation in enantioselectivity of this system was explored. After parameter optimisation, very good to excellent enantioselectivity was achieved. Control experiments confirmed that the origin of enantioselectivity arises from remote cooperative interactions between the functionalities in the active site. The catalysts were then tested for classical performance metrics and a hypothetical transition state within the MOF pore was proposed. This work establishes RAI as an alternative platform to develop high-performing asymmetric catalysts.
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    Planar chiral oxazolines based on [2.2]paracyclophane : a new toolbox for asymmetric synthesis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2024-03-07) Tewari, Shashank
    This thesis contains total 7 chapters, dealing with the synthesis of planar chiral Oxazolines based on [2.2]paracyclophane, enantiopure products obtained from their resolution, synthesis of metal-based chiral complexes, studies on C-H activation field, namely selective remote β-C-H activation of cyclic amines, and future ideas towards the goal. As the main focus of this thesis is on the development of novel planar chiral [2.2]paracyclophane derivatives, Chapter 1 starts with a brief description of [2.2]paracyclophane chemistry. A short introduction about the synthesis of key enantioenriched [2.2]paracyclophane derivatives is given. Finally, a short introduction of the recent applications of [2.2]paracyclophane-based ligands in asymmetric catalysis is also mentioned. Chapter 2 outlines a brief overview of the role of 2-oxazolines. 2-Oxazolines have been utilized in the field of asymmetric catalysis as ligands and chiral auxiliaries. The chapter briefly discusses the synthesis and highlights some of the uses of 2-oxazolines as chiral ligands. Chapter 3 describes the concise synthesis of planar chiral oxazolines based on [2.2]paracyclophanes. Various oxazoline-based compounds that were synthesized are all discussed in Chapter 3. The synthesis of mono-oxazolines coupled to [2.2]paracyclophanes, based on the methodology developed in our lab was accomplished. The next were the synthesis of bis-oxazolines and tetra-oxazolines coupled to [2.2]paracyclophane. The chapter mentions all the details and substrate scope generated with oxazolines. Chapter 4 focuses on the resolution of [2.2]paracycoplane by the hydrolysis of the oxazolines. The enantiopure products like planar chiral mono-acids, bis-acids, and partial acids were obtained by hydrolysis of the oxazolines. Apart from them, a section in the chapter describes the decarboxylative phosphorylation that was achieved through our planar chiral acids. Synthesis of planar chiral diamines via Curtius rearrangement of the diacids is also described in the chapter, followed by phanol synthesis. A part of the above chapter describes about the rhodium paddle-wheel complex formed by partial chiral acids. An attempt to make dinuclear gold complexes was made that was also successful. Overall, chapter four is the highlight of the thesis, where a lot of pure chiral products are made and their utility is explained in the field of asymmetric catalysis. Chapter 5 describes the remote β-C-H activation of cyclic amines. Attempts were made to accomplish the functionalization through the directing group strategy. The directing groups based on heterocyclic piperidine and cyclic amines were synthesized successfully. These pre-made directing groups were used for the C-H bond functionalization but the functionalization possessed many challenges that made the functionalization difficult. Chapter 6 explains the future scope of the research work mentioned in this thesis. Finally, Chapter 7 describes the experimental procedures and characterization of the synthesized compounds mentioned in Chapters 3 to 5.