Introduction
Tetrabutylammonium triphenyldifluorosilicate (TBAT, 1) is a hypervalent silicate which acts as a potent source of fluoride ions (Figure 1). The reagent has been widely exploited in organic chemistry as a means of carrying out nucleophilic fluorination reactions,
[1]
activating organosilanes as nucleophiles
[2-7]
as well as acting as a coupling reagent in palladium-catalysed reactions.
[8-10]
Figure 1
TBAT (1) is readily soluble in organic solvents, not appreciably basic, non-hygroscopic and trivial to obtain in anhydrous form. It therefore presents numerous advantages over other fluoride sources such as metal fluoride salts and tetraalkylammonium fluorides (such as TBAF) which often cause problems associated with basicity and the presence of water.
[11]
Preparation
Tetrabutylammonium triphenyldifluorosilicate (TBAT, 1) is commercially available but can also be prepared according to a simple and high-yielding procedure developed by P. DeShong and co-workers.
[12]
Triphenylsilanol (2) is treated with aqueous hydrofluoric acid (CAUTION) in methanol to produce the intermediate triphenylsilyl fluoride (3). This fluoride is then treated with TBAF to produce the hypervalent silicate TBAT (1, Scheme 1). Care must be taken when analysing TBAT since the compound is acid-sensitive and has been found to degrade in acidic solvents such as chloroform.
[12]
Scheme 1
