Hypervalent iodine compounds are increasingly been employed in contemporary organic synthesis due to their unique characteristics. These highly stable, green oxidants possess reactivity profiles comparable to transition metal catalysts but do not suffer from disadvantages such as toxicity, cost or scarcity. Although the development of hypervalent iodine chemistry and its synthetic applications has been extensively documented, the mechanistic insights for such reactions continue to remain rather limited and relatively few computational studies have been reported to date. This thesis is an attempt to comprehend the mechanistic details of reactions involving hypervalent iodine compounds using computational calculations. The mechanism for the cyclisation of N-alkenylamides, catalysed by hypervalent iodine reagent, was revealed by DFT calculations. The cyclisation of the substrate was found to be the rate-limiting step and it was found that it correlated with the ease of oxidation of the iodoarene. In contrast to the cyclisation of N-allyl and N-(but-3-en-1-yl)benzamide, cyclisation of N-(pent-4-en-1-yl)benzamide did not form the expected 7-memebered ring but instead yielded the pyrrolidine ring. DFT calculations revealed that the cyclisation of N-(pent-4-en-1-yl)benzamide at the amide oxygen was 3 kcal/mol higher in energy than cyclisation at nitrogen, hence explaining the change in mechanism. Finally, a 5-exo-dig cyclisation of δ-alkynyl β-ketoester, catalysed by precatalyst iodobenzene was also investigated using the DFT calculations. Although three different mechanisms were considered for this process; cyclisation followed by the activation of the alkyne was found to be the most likely pathway.
| Date of Award | 20 Jun 2023 |
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| Original language | English |
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| Supervisor | Wesley Moran (Main Supervisor) & Duncan Gill (Co-Supervisor) |
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