Two-step Two-intermediate Photorelease Bolm-McCulla Reaction: Dual Release of Nitrene and Atomic Oxygen Reactive Intermediates

This article is a highlight of the paper by Isor et al. in this issue of Photochemistry and Photobiology. It describes the photolysis of a dibenzothiophene sulfoximine (bearing N-phenyl imino and S-oxide groups) to produce two reactive intermediates in tandem. The sulfoximine undergoes a S-N and S-O photocleavage to release phenyl nitrene and atomic oxygen [O(³ P)]. The phenyl nitrene dimerizes to azobenzene or is trapped by diethylamine to reach an azepine. From there, atomic oxygen arises in a secondary photolysis of dibenzothiophene sulfoxide. A computational analysis also reveals that the S-N bond is labile for initial nitrene release, with the secondary release of atomic oxygen by S-O cleavage. Whether future sulfoximine scaffolds can produce the reverse order release of O(³ P) then nitrene, or release both simultaneously, is yet to be established. Nonetheless, molecules with dual-intermediate release, such as coupled photoaffinity labeling and cellular oxidation, are worth pursuing.