Oxidative processes often lead to the formation of reactive intermediates such as radicals and radical ions. Oxidation of oximes and oxime ethers yields iminoxyl radicals and oxime ether radical cations, respectively, which when formed in cells may cause damage to tissues and DNA. The reactivity of these intermediates is largely unexplored and to learn about the fundamental reactivity of iminoxyl radicals and oxime ether radical cations, we have begun an investigation on intramolecular reactions of oximes and oxime ethers using built-in alkenes as a potential nucleophile or radical trap. Previously, built-in alkynes and aromatic rings were explored as radical traps or nucleophiles. Alkyne compounds were found to react as radical traps because they only cyclized with the oximes, which is indicative of an iminoxyl radical intermediate. Compounds with built-in aromatic rings were found to react exclusively with the oxime ethers, which is indicative of a radical ion intermediate with the aromatic ring acting as the nucleophile. This project explores the reactivity of alkene functional groups under similar oxidative conditions. We hypothesize that the alkene may act as both a nucleophile and as a radical trap to form a cyclized product. Photolysis of the substrate in the presence of a sensitizer leads to the formation of the radical or radical cation intermediate that can cyclize. Preliminary results suggest that cyclization occurs with both 2-vinylbenzaldoxime and 2-vinylbenzaldoxime methyl ether. NMR analysis of both reaction mixtures upon irradiation at 420 nm with 9,10-dicyanoanthracene (DCA) for up to 4 hours shows the formation of new products over time. The NMR spectra are most consistent with structures formed via a cyclization pathway. These results are similar to the reactions of the molecules with built-in aromatics and alkynes, suggesting a potential dual-reactivity with the built-in alkenes. Further analysis of the reaction mixtures, as well as those of other substrates is currently ongoing. The NMR results coupled with GC/MS analysis of the reaction mixtures will give us a comprehensive outlook on exactly which products are being formed in each reaction, providing valuable information about the overall mechanism(s).

Nucleophile, radical trap, or both? The potential dual reactivity of alkenes in the intramolecular reactions of iminoxyl radicals and oxime ether radical cations

251st National Meeting (2016)

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