Shrey Patel Graduate Student, Department of Chemistry University of Georgia Learn more about the speaker Thursday, April 14, 2022 - 11:10am Chemistry Building, Room 400 Organic Seminar Nucleophilic substitution reactions are at the heart of synthetic organic chemistry. While conventional strategies for conducting nucleophilic substitution reactions have been heavily studied, we hereby report the development of the novel photochemical approach to the induction of nucleophilic substitution reactions. This strategy employs a light-activated leaving group based on the 9-aryl-9-fluorene system. 9- fluorenol undergoes efficient photolysis of the C–O bond due to the stability of the aromatic 4π cyclic fluorenyl cation in the excited state. The photo-generated fluorenyl cation is anti-aromatic in the ground state and, therefore, extremely reactive. It rapidly undergoes cyclization, activating the leaving group and increasing the electrophilicity of the substrate. This report provides the first example of a photo-SN1 reaction. We will discuss the initial exploration of the new reaction's scope, testing of various structural modifications, solvent systems, and nucleophiles. Furthermore, the utility of this method for photoglycosylation in sugars is being explored. Additionally, an approach for conducting photo-SN2 reactions will be discussed. References Wan, P.; Krogh, E., Evidence for the generation of aromatic cationic systems in the excited state. Photochemical solvolysis of fluoren-9-ol. Journal of the Chemical Society, Chemical Communications 1985, (17), 1207. Gaillard, E.; Fox, M. A.; Wan, P., A kinetic study of the photosolvolysis of 9-fluorenol. Journal of the American Chemical Society 1989, 111 (6), 2180-2186. Mecklenburg, S. L.; Hilinski, E. F., Picosecond spectroscopic characterization of the 9-fluorenyl cation in solution. Journal of the American Chemical Society 1989, 111 (14), 5471-5472. Wan, P.; Krogh, E., Contrasting photosolvolytic reactivities of 9-fluorenol vs. 5-suberenol derivatives. Enhanced rate of formation of cyclically conjugated four .pi. carbocations in the excited state. Journal of the American Chemical Society 1989, 111 (13), 4887-4895. McClelland, R. A.; Mathivanan, N.; Steenken, S., Laser flash photolysis of 9-fluorenol. Production and reactivities of the 9-fluorenol radical cation and the 9-fluorenyl cation. Journal of the American Chemical Society 1990, 112 (12), 4857-4861.