Date of Award
Master of Science (MS)
Department of Chemistry
Andrew TAM Mitchell
The cycloaddition reaction is an important transformation in the field of organic chemistry since it serves as an indispensable tool in organic synthesis. The oxidopyrylium-based [5+2] cycloaddition reaction has received enormous attention in chemical synthesis due to its usefulness in the formation of seven-membered heterocyclic ring systems present in bioactive natural products.1,2,3,4 In spite of the tremendous attention paid to this reaction, there still exist stereo and regioselectivity limitations. Further investigation is critical in light of these limitations. The intramolecular oxidopyrylium-based [5+2] cycloaddition is known to afford these ring systems with high stereo and regioselectivity since with the intramolecular type the olefin is always tethered to the pyrone. Previous work by the Mitchell research group revealed bulky transfer group, alkene substitution, and proximity of the tether to the transfer group to be of great importance for intramolecular oxidopyrylium-based [5+2] cycloadditions.5 Again, the Mitchell research group has demonstrated a room temperature intramolecular oxidopyrylium-based [5+2] cycloadditions for enamine-based reactions.6 To further extend the previous work in the Mitchell research group and establish an alternative approach for the intramolecular oxidopyrylium based [5+2] cycloadditions, N-heterocyclic carbine (NHC) catalyzed [5+2] cycloaddition was envisioned. Effort towards this work is the synthesis silyloxypyrone-ester which when subjected to enolate chemistry will afford the corresponding cycloadduct. We have established silyloxypyrone-aldehyde as a useful intermediate for the synthesis of many synthetic valuable pyrones. Again, we have established amides as useful functionality for intramolecular oxidopyrylium-based [5+2] cycloadditions with tert-butyl group enabling this reaction.
Darko, Kwabena, "Investigation of Intramolecular Oxidopyrylium-Based [ 5 +2 ] Cycloadditions" (2023). Theses and Dissertations. 1729.