Regioselective functionalization of pyridines and other azines
Date
2021
Authors
Boyle, Benjamin T., author
McNally, Andrew, advisor
Chen, Eugene, committee member
Ackerson, Chris, committee member
Montgomery, Tai, committee member
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Abstract
Pyridines and diazines serve as cores in pharmaceuticals and are common motifs in organomaterials and ligands. Selective functionalization of these motifs is of importance for discovery and optimization of new bioactive molecules. Pyridine functionalization is of interest for synthetic chemists, and despite modern advances in derivatization challenges and limitations remain. Chapter one focuses on the impact of pyridines and diazines in the pharmaceutical industry. Classical and modern methods for C-H functionalization are discussed. Chapter two describes work on phosphorus ligand-coupling for bisazine synthesis using a three-stage protocol. This method provides an alternative to traditional metal-catalysis for bisazine synthesis and can be applied to drug-like fragments. This work is expanded on in chapter three by using a tandem SNAr-ligand-coupling strategy for bisazine synthesis, in particular 2,2'-bipyridines. Chapter four describes a facile SNAr reaction by phosphines on iodopyridines. A bis-salt N-phopsphonium pyridinium is the key intermediate and provides a broad scope of reactivity. Chapter five shifts towards functionalization of the 3-position of pyridine through a Zincke-type intermediate. By exploiting a ring-opening-functionlization-rearomatization strategy a selective halogenation of pyridines was achieved. The Zincke imine intermediate is also viable for other functionalizations and provides products directly from the C-H bond on the initial pyridine.
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Subject
pharmaceuticals
pyridines
ligand coupling
Zincke
phosphorus