Photocontrolled Retro-Ene Reaction for Triazolinedione Release from Indole Adducts
Jingwen Wang1, Leixing Du1, Yu Hai1
1Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces, College of Chemistry and Materials Science, Zhejiang Normal University, 688 Yingbin Road, Jinhua, 321004, P. R. China.
Abstract:
TAD-indole adducts are valuable surrogates for triazolinediones (TADs) in bioconjugation and polymer chemistry, yet current retro-ene activation is constrained by elevated temperatures (>40 °C) or mechanical force with bulky side chains. We introduce a photoactivated retro-ene strategy liberating TADs under mild conditions. Upon excitation, adducts undergo efficient retro-ene release, with liberated TADs trapped by thiols (urazoles) or dienes (Diels-Alder adducts). The wavelength is tunable via the C2 indole substituent: the 2-phenyl adduct requires 370 nm, whereas 2-phenanthryl or 2-pyrenyl analogues respond to 370-420 nm or 370-460 nm, enabling precise photocontrol. Remarkably, release proceeds even at -78 °C. Combining this method with our direct synthesis from indoles and urazoles establishes a recyclable system among these components, promising for recyclable polymers. Additionally, efficient ligation with a tyrosine derivative opens avenues for peptide and protein labeling.
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