Abstract
An alternative method for generating arynes from ortho-silylaryl triflates using cesium carbonate and 18-crown-6 is reported. The method was efficiently applied to a variety of reactions between several arynes and arynophiles. We also demonstrated that the efficiency of aryne generation is significantly affected by the alkali metal countercation of the carbonate.
Highlights
Arynes are highly reactive intermediates useful for preparing diverse aromatic compounds [1,2,3,4,5,6,7,8].Novel transformations of arynes have been achieved and applied to the synthesis of a wide range of complex aromatic compounds
As a part of our studies focusing on highly strained alkynes, including arynes [24,25,26,27,28,29,30,31,32,33,34], we have been working on a project to develop new aryne generation methods
1a using cesium carbonate, we found that addition of 18-crown-6-ether dramatically accelerates benzyne generation, affording the product 3 in high yield, even when the reaction is performed at 25 °C [37]
Summary
Arynes are highly reactive intermediates useful for preparing diverse aromatic compounds [1,2,3,4,5,6,7,8]. Novel transformations of arynes have been achieved and applied to the synthesis of a wide range of complex aromatic compounds. Activation of ortho-silylaryl triflates with a fluoride ion is one of the most widely-used methods for generating arynes [9]. We report that cesium carbonate, in the presence of a crown ether, serves in place of a fluoride ion as an efficient activator for generating arynes from ortho-silylaryl triflates
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