Access to Arynes from Arenes via Formal Dehydrogenation: Increased Efficiency and Scope, Synthetic Applications and Mechanistic Analysis

Arynes undergo a wide range of diverse chemical transformations making them highly versatile reactive in-termediates for organic synthesis. Access to arynes has long been dominated by pre-functionalized reagents such as the venerable o-trimethylsilylaryl triflate class of substrates. However, a move toward the development of methods to access arynes that are both mild and efficient has prompted research into aryl “onium” aryne precursors. We have leveraged aryl “onium” species as intermediates in an overall net dehydrogenation of simple arenes as an efficient way to generate and trap arynes. Herein, we describe two strategies to achieve mild and efficient access to arynes. 1) The development of a one-pot method that converts simple arenes into aryl thianthrenium salts and uses them in situ to generate arynes; the net transformation of arene to trapped aryne is achieved within two hours. 2) The development of a two-step process to convert arenes into aryl(Mes)iodonium salts and ultimately trapped arynes to expand the scope of arenes compatible; the net transformation is complete within four hours. Mechanistic analysis through competition experiments, deuterium kinetic isotope effects (DKIE) and Density Functional Theory (DFT) provide key insight into the similarity and differences of the two approaches described in this work and yield a user’s guide for selecting the appropriate strategy based on the arene.