Focus: N,N-Diethylaminosulfur trifluoride (DAST, Et2NSF3) and related reagents

Abstract

N,N-Dialkylaminosulfur trifluorides were first prepared in 1964 ^[1] and have since been developed as mild, easily handled fluorinating agents. ^[2] DAST, [38078–09–0], the most widely used member of this family of reagents, is a pale yellow liquid that reacts violently with water. DAST is readily obtained from commercial sources (e.g. Aldrich or Lancaster) and can also be prepared by the reaction of N,N--di-ethylaminotrimethylsilane with sulfur tetrafluoride, followed by distillation of the crude product under reduced pressure. ^[3] DAST is known to be thermally unstable, undergoing either explosion or detonation when heated to > 9°ºC. ^[4] The more thermally stable bis(2-methoxy-ethyl) aminosulfur trifluoride (Deoxo-Fluor™, [202289–38–1]) has recently been made commercially available (Aldrich; Air Products and Chemicals) and is reported to have similar reactivity to DAST.^[5]