Palladium―Catalyzed Reactions of 2―Silylaryl Triflates for the Synthesis of Cyclic Organosilanes

2 & horbar;Silylaryl triflates such as 2 & horbar;(trimethylsilyl)phenyl triflate, known as Kobayashi reagent, have been widely used as efficient aryne precursors in organic synthesis, and various synthetic transformations have been developed based on this approach to date. On the other hand, synthesis of new organosilicon compounds by retaining the silicon substituents of 2 & horbar;silylaryl triflates without forming arynes could be regarded as another attractive way of utilizing these compounds. In particular, silicon & horbar;containing cyclic compounds are expected to be useful for various applications such as biologically active substances and optoelectronic materials. In this regard, we have been actively engaged in developing new synthetic methods of silacycles by palladium & horbar;catalyzed reactions of 2 & horbar;silylaryl triflates without the formation of aryne intermediates. As a result, we have succeeded in the selective synthesis of various silacycles through the activation of C & horbar;H andor C & horbar; Si bonds as well as their intramolecular bond exchange process with C & horbar;Pd bonds that are generated during the catalytic reactions. The target compounds of our reactions include silicon & horbar; stereogenic dibenzosiloles, highly substituted benzosilacyclobutenes, silicon & horbar;stereogenic 5,10 & horbar; dihydrophenazasilines, benzophenanthrosilines, benzofluorenosilepins, silabenzoxazines, and tetrahydrophenanthrosiloles. Herein an overview of these transformations is described along with their mechanistic aspects.