Diethylaminosulfur Trifluoride (DAST)

Abstract

Fluorination is an important structural modification for ­diverse classes of bioactive organic molecules. The introduction of a fluorine atom or fluorinated group into organic molecules often changes their physical, chemical and physiological properties, resulting in greater stability and lipophilicity of the molecule. [1] Diethylaminosulfur trifluoride (DAST) is a widely used fluorinating reagent, [2-6] which is very effective for converting alcohols, ketones, aldehydes and carboxylic acids into their corresponding fluoro derivatives. This reagent has its origins in the ­pioneering work of Middleton et al. at DuPont. [7] DAST is synthesized via the substitution of a fluorine atom of ­sulfur tetrafluoride (SF4) by a diethylamino group, resulting in a powerful fluorination agent (Scheme 1). DAST presents the following advantages: the product is rela­tively easy to handle and shows good selectivity, con­sequently being less prone to formation of olefins in elimination reactions and/or rearrangement reactions. This reagent is commercially available as liquid that can be handled at room temperature and in common laboratory glassware. However, DAST is unstable above 70 °C.