Facile Synthesis of Rhodamine Esters using Acetyl Chloride in Alcohol Solution

Abstract

The rhodamines are a highly fluorescent class of compound used in many different fields of research, from the lasing medium in dye lasers to biological stains and markers for cellular drug resistance. In this study, esters (2–7) of rhodamine 110 (1) were conveniently prepared via the addition of acetyl chloride to a solution of the free acid (1) in the appropriate alcohol. This method conferred several advantages over previous preparations, namely that for low boiling alcohols, simple evaporation of the solution afforded the ester in quantitative yield with no need for purification. For higher boiling point alcohols, a method has been developed which allows the separation of longer chain esters from the alcohol solvent.

Keywords:

• Rhodamine
• esterification
• acetyl chloride
• lipophilicity

Acknowledgments

We thank Graham MacFarlane (School of Molecular and Microbial Sciences, University of Queensland) for accurate mass measurements. This work was supported by funds from the Centre for Biophotonics and Laser Science, School of Physical Sciences, University of Queensland.