α-Hydroxytropolones (αHTs) are a class of molecules that have been identified as lead compounds for several human diseases. Prior to Murelli group studies of [5+2] oxidopyrylium cycloaddition/ring opening strategies towards aHTs, structure activity relationship studies on these molecules have been limited due to a scarcity of efficient synthetic methods to access them. Recently, we’ve described the successful adaptation of this [5 + 2] oxidopyrylium cycloaddition/ring-opening for 3,7-dihydroxytropolone (3,7-dHT) synthesis. During these studies it was found that that a stoichiometrically equivalent reaction between oxidopyrylium dimer and halogenated alkyne takes place quantitatively at elevated temperatures. The oxidopyrylium ylides are generated through the cycloreversion of oxidopyrylium dimers, which provides a ‘clean’ source of ylide absent from base and/or acid commonly present as reagents or byproducts using standard intermolecular oxidopyrylium cycloaddition procedures. Therefore, in cases where the reaction is quantitative, the reaction mixture only contains product and solvent, and thus highly pure material can be obtained after removal of solvent. As the method works particularly well with iodoalkynes, we also describe examples of modifications of the resultant iodide-containing bicycles. Finally, we describe how by adding an alcohol incorporation, αHTs, as well as 3,7-dHTs, can be synthesized using stoichiometrically equivalent, intermolecular [5+2] oxidopyrylium cycloadditions with halogenated alkynes.

Synthesis of highly oxygenated troponoids utilizing oxidopyrylium cycloaddition chemistry

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.