Development of new methods for the synthesis of five-, six-and seven-membered heterocyclic compounds

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2019
Karadeniz, Eda
Synthesis of heterocyclic compounds has become an important area among organic chemists since they occupy a unique position in the design and synthesis of novel biologically active agents that exhibit noteworthy medicinal activities. In this regard, N-propargylic β-enaminones have been recognized as valuable substrates in synthesis because they afford a variety of heterocyclic compounds upon treatment with proper reagents. In this study, new reactivity patterns of N-propargylic β-enaminones were investigated in order to synthesize different heterocyclic compounds. Accordingly, in the first part of study, 5-iodopyridines were prepared by electrophilic cyclization of N-propargylic β-enaminones, and then their Suzuki-Miyaura coupling reaction with boronic acids were investigated to afford 5-aryl-substituted pyridines. Secondly, a facile one-pot method for the synthesis of 2-ferrocenylpyridines has been established. The reaction of α,β-alkynic ketones with propargylamine produced N-propargylic β-enaminones in situ, which, in the presence of copper(I) chloride, have underwent electrophilic cyclization to furnish 2-ferrocenylpyridine derivatives. Thirdly, an efficient method for the synthesis of spiro-2H-pyrroles has been developed. When reacted with 1-ethynylcyclohexylamine, α,β-alkynic ketones produced cyclohexane-embedded N-propargylic β-enaminones, which, upon treatment with cesium carbonate, yielded spiro-2H-pyrrole derivatives via nucleophilic cyclization. In addition, cyclohexane-embedded N-propargylic β-enaminones were further functionalized with aryl iodides. Subsequently, when these arylated β-enaminones were exposed to cesium carbonate mediated nucleophilic cyclization, they produced spiro-2H-pyrroles with two carbonyl groups via further benzylic C-H oxidation. In the last part, a different approach have been employed for the synthesis of spiro-1,4-oxazepines. Upon treatment with zinc iodide and silver hexafluoroantimonate, cyclohexane-embedded N-propargylic β-enaminones produced spiro-1,4-oxazepines.

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Citation Formats
E. Karadeniz, “Development of new methods for the synthesis of five-, six-and seven-membered heterocyclic compounds,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Chemistry., Middle East Technical University, 2019.