Arynes are unique aromatic species that display versatile reactivity in a variety of transformations. It has been demonstrated that the reaction profiles of arynes can be altered by transition metal additives, and one of the earliest examples of the metal additive effect was observed with silver ions (Ag⁺). Especially, in the presence of Ag⁺, benzyne showed distinctive reactivity and selectivity toward π-nucleophiles compared to the corresponding reaction in its absence. Although more experimental data need to be accumulated to accurately define the Ag⁺ additive effect, based on its role displayed in various transformations, we can infer that Ag⁺ interacts with arynes to form a reactive intermediate, which behaves like a silver-bound aryl cation or 1,2-carbene-silver carbenoid. In this tutorial review, various aryne-mediated reactions involving Ag⁺ or other organosilver species are discussed, which show a bird's-eye view on the Ag⁺ effect in aryne chemistry such that further explorations of the unique reactivity of arynes under the influence Ag⁺ will be inspired.

The direct metal-catalyzed [1,3]-transposition of allylic alcohols and allylic silyl ethers is a synthetically useful isomerization process that occurs via [3,3]-sigmatropic rearrangement induced by high oxidation state oxometal complexes. The isomerization requires only a catalytic amount of promoter, and high chirality transfer can be achieved. Thus, it bears a significant potential to become a powerful tool in multistep synthesis. Although [1,3]-transposition of allylic alcohols has been known since the late 1960s, the development of synthetically useful protocols that allow for a high level of regio- and stereoselectivity control and their synthetic applications have emerged only recently. This tutorial review summarizes recently developed regioselective [1,3]-transpositions of allylic alcohols and silyl ethers and their applications to natural product synthesis.