Preparation and NMR studies of hypervalent silicates and their use in palladium-catalyzed cross-coupling reactions

In previous years, there have been numerous advances in the formation of carbon-carbon bonds by palladium-catalyzed cross coupling reactions. In particular, considerable effort has been devoted to the study of the Stille and Suzuki reactions. Cross coupling reactions are valuable to the field of synthetic chemistry because they provide a versatile and efficient route to the formation of complex molecules from relatively simple starting materials.; A subset of the cross coupling reaction which employs hypervalent silicon reagents as the nucleophilic species in the coupling has been developed in our laboratory. These hypervalent silicates allow for the efficient transfer of aryl groups including heteroaryl species. This process may be carried out using preformed hypervalent salts or through the generation of reactive hypervalent intermediates in situ.; In addition to participating in palladium-catalyzed cross coupling reactions, our laboratory has also shown that hypervalent silicates may be generated in situ for the transfer of other nucleophiles. Hypervalent silicates have been shown to transfer cyanide and azide efficiently in SN2 displacements involving primary and secondary alkyl halides and sulfonates. Spectroscopic evidence has been obtained suggesting the intermediacy of such hypervalent silicates as the reactive species in these processes.