Intramolecular Oxazolium Salt/Azomethine Ylide Cycloaddition Reactions with Varying Dipolarophile Tether Position

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Student Presentation

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Don Warner


Pyrroles and pyrrolidines are heterocyclic compounds that are particularly useful for medicinal purposes. They can be found in an assortment of biological contexts, such as cofactors and secondary metabolites, and are present in a range of drugs that treat everything from cardiovascular disease to cancer. Engineering these compounds can be accomplished through a multitude of ways, but a 1,3-dipolar [3+2] cycloaddition may prove to be beneficial in producing lucrative pyrroles or pyrrolidines. This research aims to expand the scope of the known oxazolium salt/4-oxazoline/azomethine ylide route in the assembly of five member heterocycles via azomethine ylide formation through a nucleophile-mediated opening of an oxazolium salt. This methodology generates the reactive formation of the azomethine ylide under mild conditions allowing sensitive functional groups to be preserved. Only the 5-substituted and 2,5-disubstituted oxazoles are known to undergo this transformation ring-open under these conditions. However, a dipolarophile tethered at the five position have been shown to undergo an intramolecular cyclization. Thus, we are focusing our efforts on varying the position of the dipolarophile tether to the position two carbon and position three nitrogen. Preparation of all intermediates and progress to date will be reported.

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