Hiyama-Denmark coupling

Denmark and his co-workers recently reported a series of the palladium-catalyzed coupling reactions of alkenylsilicon compounds with aryl iodides. Thus, ( )- or (Z)-alkenylsilacyclobutanes, which are readily prepared by the reaction of the corresponding alkenylaluminum compounds with chlorosila-cylobutanes or the reduction of alkynylsilacyclobutanes, respectively, were found to be active nucleophiles to react with aryl iodides in 10 min at room temperature in most cases (Eq. 13) [17]. Later, it was clarified that silacyclobu-tanes were first converted into alkenyl(propyl)silanols by hydrolysis under the reaction conditions [18], and these were shown to be truly active species. Alkenylsilanols actually react with aryl iodides under the similar conditions (Eq. 14) [19,20]. Independent study by Hiyama and Mori revealed that silver(l) oxide also is an excellent activator for the palladium-catalyzed coupling of alkenylsilanols with an aryl iodide (Eq. 15) [21]. Very recently Denmark... 

A particularly noteworthy variant of the Hiyama coupling is the Denmark modification." Silacyclobutanes... 

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