Towards bioresource-based aggregation-induced emission luminogens from lignin β-O-4 motifs as renewable resources

作者：Tenglong Guo, Yuting Lin, Deng Pan, Xuedan Zhang, Wenqing Zhu, Xu‐Min Cai, Genping Huang, Hua Wang, Dezhu Xu, Fritz E. Kühn, Bo Zhang, Tao Zhang · 发表于：Nature Communications · 年份：2023 · DOI：10.1038/s41467-023-41681-0 · 被引用次数：45 · 研究领域：Radical Photochemical Reactions、Oxidative Organic Chemistry Reactions、Catalytic C–H Functionalization Methods

One-pot synthesis of heterocyclic aromatics with good optical properties from phenolic β-O-4 lignin segments is of high importance to meet high value added biorefinery demands. However, executing this process remains a huge challenge due to the incompatible reaction conditions of the depolymerization of lignin β-O-4 segments containing γ-OH functionalities and bioresource-based aggregation-induced emission luminogens (BioAIEgens) formation with the desired properties. In this work, benzannulation reactions starting from lignin β-O-4 moieties with 3-alkenylated indoles catalyzed by vanadium-based complexes have been successfully developed, affording a wide range of functionalized carbazoles with up to 92% yield. Experiments and density functional theory calculations suggest that the reaction pathway involves the selective cleavage of double C-O bonds/Diels-Alder cycloaddition/dehydrogenative aromatization. Photophysical investigations show that these carbazole products represent a class of BioAIEgens with twisted intramolecular charge transfer. Distinctions of emission behavior were revealed based on unique acceptor-donor-acceptor-type molecular conformations as well as molecular packings. This work features lignin β-O-4 motifs with γ-OH functionalities as renewable substrates, without the need to apply external oxidant/reductant systems. Here, we show a concise and sustainable route to functional carbazoles with AIE properties, building a bridge between lignin and BioAIE mate...