Dr. Tom Hoye, University of Minnesota

Host: Dr. VanVeller

For the last decade we have been advancing the generality of a process that we call the hexadehydro-Diels–
Alder (HDDA) reaction1. This net [4+2] cycloisomerization produces an o-benzyne derivative, which is then
rapidly captured in a subsequent trapping event. The HDDA reaction is a rare example of a transformation that
generates a highly reactive intermediate by way of a highly exergonic (ca. –50 kcal•mol-1) reaction! This twostage,
benzyne generation-trapping cascade results in the rapid assembly of structurally complex benzenoid
products. This chemistry is both preparatively valuable and mechanistically instructive. Recent examples of
formal biomolecular HDDA reactions2 and one-pot room-temperature substrate assembly and
cycloisomerizations3 will be shown.

Recently we have uncovered reactions of HDDA benzynes as well as some off-the-shelf (i.e., storable)
electrophilic alkynes that give rise to other types of transient, high-potential energy, reactive intermediates –
namely, a,3-dehydrotoluenes,4 cyclic allenes, and carbenes. A few of these transformations will be presented
near the end of the lecture.