Smooth photogeneration of α,n-didehydrotoluenes (DHTs)

Irradiation of the three isomeric (chlorobenzyl)trimethylsilanes in methanol–water generates the corresponding didehydrotoluenes (DHTs). The process involves expulsion of a chloride ion to give the triplet phenyl cation and ensuing elimination of the trimethylsilyl cation. This straightforward generation of DHT intermediates overcomes a shortcoming of previous methodology (cycloaromatization of enyne-allenes), which is limited to the meta-isomer, and opens the path for understanding the chemistry (and possibly the biological action) of these unusual intermediates.