Hypervalent silane and siloxane reagents (preformed or generated in situ) for transmetalation in palladium catalyzed reactions with derivatives of allylic alcohols, aryl halides, electron-withdrawing aryl bromides, and aryl triflates derived from phenols are disclosed. Also disclosed are methods of preparing glycosyl azides by reaction of an azide with a silyl ester in the presence of a phoshine.