Fluorescence spectroscopy employing small molecule reporters has proven to be a powerful technique for biological imaging and detection applications. Synthetic efforts continue to develop fluorescent tools with improved photophysical properties, luminescent responses, and desired imaging properties. Fluorophores incorporating hydroxyl units as the donor moiety are inexpensive and readily available but often exhibit less desirable luminescent properties and limited tunability compared to their amino variants. An operationally simple method has been developed for synthesizing <i>N</i>-aryl and <i>N</i>-alkyl aminofluorophores from their hydroxylated parent. The process exploits a key Smiles rearrangement under mild basic conditions using simple bromoacetamides as the aminating unit. The method has been applied for the synthesis of a broad range of aminocoumarins and can also provide access to amino variants of xanthene fluorophores, such as rhodols. The transformation can be telescoped into a one-pot process and provides an expedient and convenient alternative to transition-metal based amination strategies.

Amination of hydroxyfluorophores using a Smiles rearrangement strategy

ACS Spring 2022

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