Azide and cyanide displacements via hypervalent silicate intermediates

Hypervalent azido- and cyanosilicate derivatives, prepared in situ by the r eaction of trimethylsilyl azide or trimethylsilyl cyanide, respectively, wi th tetrabutylammonium fluoride, are effective sources of nucleophilic azide or cyanide. Primary and secondary alkyl halides and sulfonates undergo rap id and efficient azide or cyanide displacement in the absence of phase tran sfer catalysts with the silicate derivatives. Application of these reagents to the stereoselective synthesis of glycosyl azide derivatives is reported .