Use of the Carbonyl group as a Nucleophile in Photosensitized Electron Transfer Reactions of Oxime Ethers
Authors:Neha Ansari, Brittany Grassbaugh, Aneta Jelowicki
Mentor:Peter de Lijser, Professor of Chemistry, California State University, Fullerton
Oxime and oxime ethers are organic compounds commonly found in pesticides, drugs, and material chemistry. Oxidation of these compounds leads to the formation of reactive intermediates, such as radicals and radical ions, the reactivity of which is relatively unknown. Our research focuses on obtaining a better understanding of the structure and reactivity of the reactive intermediates formed in the oxidative processes of simple oximes and oxime ethers. Previous work has shown oxime ethers to react with nucleophiles at the nitrogen of the oxime moiety. This observation suggests that oxime ethers with built-in nucleophiles can react faster and yield novel heterocyclic products that are of interest for drug synthesis. In this project, we have investigated the use of the b-carbonyl group as an effective nucleophile in the photooxidation reactions of a series of oxime ethers. The O-benzyl ethers of 2,4-pentanedione, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione were prepared and subjected to photolysis for up to 4 hours (and sometimes overnight) in the presence of a photosensitizer. The reactions were followed by NMR and GC/MS. The NMR studies revealed the formation of new absorptions in the aromatic and aliphatic regions. Analysis by GC/MS of the reaction mixture of the diphenyl derivative suggested the formation of a cyclic product, however, NMR analyses were not consistent with that conclusion. GC/MS analysis of the reaction mixtures of the other two derivatives indicates the formation of a new product with the same molecular weight as the starting material but a different fragmentation pattern and retention time, suggesting a rearrangement might have taken place. In this presentation, we will discuss the results of these studies and propose potential mechanisms for the products on the basis of their NMR and MS spectra in light of what is known about the reactivity of these types of compounds.