Hexadehydro Diels-Alder (HDDA) Route to Arynes and Related Chemistry

The title reaction, first revealed in 1997, has seen expansive growth since a report in 2012 demonstrated its potential as a general strategy for creating reactive benzyne intermediates from simple triyne precursors. In contrast to the presence of reagents (and their byproducts) used in the vast majority of the classical methods for aryne formation seen in the Chapters 1, 8 and 9 in this Handbook, the simple thermal reaction conditions used for hexadehydro Diels-Alder (HDDA)-benzyne generation are pristine. This often allows for new types of aryne-trapping reactions and for new mechanistic insights to be revealed. Examples of these can be seen in the selections presented in this chapter. Guidelines for designing new HDDA studies, from both strategic and experimental design perspectives, are presented in the last several pages.