Diethylaminosulfur trifluoride (DAST) was the first major advance in deoxofluorination reagents developed from sulphur tetrafluoride. Unlike sulphur tetrafluoride, DAST is a liquid, which makes its handling, use and storage safer and more convenient. DAST was first used in the mid-1970s around 13 years after sulphur tetrafluoride first emerged. It shares some of the disadvantages of sulphur tetrafluoride, such as violent reactivity with water to liberate HF and thermal instability; decomposing explosively at elevated temperatures. It is, therefore, stored in a freezer to maintain quality, as well as for safety reasons. DAST is an extremely effective fluorinating agent, and is regularly produced in multi-kg quantities at Cheshire Organics. Our state-of-the-art facilities and expertise also mean that this useful reagent is often used in a range of fluorination projects for our clients.

Some examples of DAST mediated deoxofluorinations are illustrated below.