Improved Substrate Scope and Linker Optimization for Coumarin-Based Smiles Rearrangement

Fluorophores are light-emitting compounds that are utilized mainly in fields such as environmental testing, biological imaging and even forensics. Fluorophore molecules are consisted of the fluorescent portion, a chromophore moiety, and an attached donor group. Although the commonly found, hydroxy substituted fluorophores are cheaper and easier to make, the amine substituted fluorophores circumvent many of the problems that accompany the hydroxyl group. Nitrogen-substituted fluorophores generally have improved photostability, pH sensitivity and more synthetic tunability than the oxygen-containing fluorophores and thus are more desirable to the aforementioned fields. However, the previous method of synthesizing the nitrogen-containing fluorophores use a complex, multi-step process with metallic catalysts and high temperatures. Our group has recently developed a method to synthesize these nitrogen-containing fluorophores without the use of the metallic catalysts that works on a much wider substrate scope. Previous work was focused on the expansion of the substrate scope for this novel reaction to show the versatility and breadth of the reaction process. Current efforts are being focused on exploring the scope and efficacy of the utilization of new dicarbonyl linkers and its ability to react both faster and with a wider range of substrates. We hypothesize that the electron poor, carbonyl carbons produced by the dicarbonyl linker should allow a broader range of aniline and phenol components. It is anticipated that the use of the dicarbonyl linker will produce a reaction mechanism that is effective on an even greater variety of substrates while proceeding through the process more quickly