Here we describe our work in using computational chemistry to determine the overall scope of an oxime ether radical cation route towards heterocycles.  Heterocycles are a reoccurring motif in organic chemistry and are commonly found in pharmaceuticals, pesticides and dyes. One possible way to synthesize heterocycles is through the cyclization of oximes or oxime ethers, often using metal catalysts or harsh reaction conditions. Recent experimental work in the de Lijser laboratory at California State University, Fullerton has focused on developing a more environmentally friendly approach using photo-induced electron transfer (PET) to produce oxime ether radical cation reactive intermediates that subsequently undergo intramolecular cyclization. Specifically, they have focused on benzaldehyde oxime ethers that contain a furan or thiophene group. Experimental studies show that the compounds containing a thiophene group produce 90-95 percent yield of cyclized product after PET whereas compounds with a furan group produce less cyclized product. Previously, our lab has used density functional theory to understand the reaction mechanism and explain trends in the experimental percent yields. Currently, we are using computational chemistry approaches to screen a large number of thiophene and furan group containing benzaldehyde oxime ethers for their propensity to cyclize as radical cations.  Specifically, we use thermally averaged ionization potentials, calculated at the ωB97M-V/def2-QZVPP// ωB97X-D/cc-pvdz level of theory, to examine the effects of electron-donating and electron-withdrawing substituents on the ionization potential and hence the ease of oxidation via PET. In doing so, we make predictions about reactions that have not yet been explored experimentally as well as develop insights into the overall scope of the PET cyclization approach towards synthesizing heterocycles from benzaldehyde oxime ethers.<br/>

Computational study of substituent effects on the intramolecular cyclization of benzaldehyde oxime ethers containing a thiophene or furan group

2019 Spring National Meeting

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