The bis-allylic nature of the diradical intermediate is the basis of a novel photochemical rearrangement of cycloadducts 1, which are easily obtained by intermolecular Pauson-Khand reaction of norbornadiene with alkynes, to tricyclo[5.2.1.02,6]deca-3,8-dien-10-ones 2 in good yields. This photorearrangement tolerates a wide variety of functional groups.
![Photochemical rearrangements of norbornadiene Pauson–Khand cycloadducts](https://www.iciq.org/wp-content/uploads/2014/03/Photochemical-rearrangements_eng_noticies_articles_2007_86.gif)