Related Experiment Video
Updated: Jul 10, 2026

Harnessing the Bioorthogonal Inverse Electron Demand Diels-Alder Cycloaddition for Pretargeted PET Imaging
Published on: February 3, 2015
Chemoselective photorearrangements of diazinobarrelenes. Deuterium labeling study
Ann-Cheng Chen1, Gary J Chuang, Nelson R Villarante
1Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan.
Abstract:
Chemoselective photorearrangements of pyrazino-, quinoxalino-, and benzoquinoxalinobarrelenes were investigated by deuterium-labeling experiment. Photolysis of pyrazinobarrelene 4 and quinoxalinobarrelene 5 with 300 nm region light under either direct or sensitized conditions afforded semibullvalenes 7 and 8, respectively; benzoquinoxalinobarrelene 6 was inert to both reaction conditions. Irradiation of deuterated pyrazinobarrelene 4-d4 and quinoxalinobarrelene 5-d4 afforded deuterated semibullvalenes 7-d4-A-7-d4-F and 8-d4-A-8-d4-F, respectively. Of the two a priori possibilities of bridging, the deuterium-labeling experiment has shown that deuterated pyrazinobarrelene 4-d4 afforded 98% (C6D6) and 95% (CD3CN) of semibullvalenes generated through aryl-vinyl (A-V) bridging, whereas the quinoxalinobarrelene 5-d4 furnished 79% (C6D6) and 71% (CD3CN) of semibullvalenes generated through vinyl-vinyl (V-V) bridging. The contrasting photochemical behavior of heteroarene-fused barrelenes 4-6 was explained qualitatively in terms of triplet energy minimization and relative stability of diradicaloid intermediates.
Related Concept Videos
¹H NMR of Labile Protons: Deuterium (²H) Substitution
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation

