Light-Induced Nucleophilic Substitution by Photo-activation of a Leaving Group

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

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