Small molecule fluorophores enjoy broad application in areas including biological imaging, environmental detection, and laser dyes. Rational synthetic modification of these compounds continues to provide new chemical tools with improved photophysical properties, sensitive and selective luminescent responses, and spatiotemporal imaging capabilities. Many commercially available or readily accessible small-molecule fluorophores incorporate a hydroxyl moiety as a donor component of the chromophore. Amino analogues of these compounds (e.g. rhodols, rhodamines, aminocoumarins) exhibit favorable photophysical properties, pH sensitivity, and synthetic tunability. An operationally simple and robust method for the conversion of hydroxyfluorophores to aminofluorophores is described using the Smiles Rearrangement as the key synthetic step. Investigation of various nitrogen-containing linkers revealed that the base-promoted rearrangement of linked amides can provide the desired products under exceptionally mild conditions. This method is anticipated to provide facile access to aminofluorophores orthogonal to current multi-step, transition-metal catalyzed processes.

Facile conversion of hydroxyfluorophores to aminofluorophores via Smiles rearrangement

2019 Spring National Meeting

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