Highly efficient transformation of lignin major segments into quinolines

• Published in: Chemical engineering science Vol. 290; p. 119899
• Main Authors: Zhu, Wenqing, Skagfjörd Reinhold, Julian, Lu, Jinfei, Xu, Dezhu, Guo, Tenglong, Luo, Wenhao, Zhang, Bo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.05.2024
• Subjects: Lignin β-O-4 segments; Quinolines; V-based catalyst; Quinolines; V-based catalyst; Lignin β-O-4 segments
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2024.119899

•A sustainable method to synthesize quinolines from lignin major segments has been successfully developed.•Redox-neutral depolymerization of lignin major segments and construction of quinoline motifs were realized in a one-pot fashion.•A tandem selective cleavage of C-O bonds/dehydrogenation/aza-Michael addition/cyclization/dehydration/oxidation sequence is proposed. The development of a sustainable synthesis route for functional quinolines from lignin β-O-4 segments containing γ-OH group is of high importance to meet biorefinery demands, but remains challenge due to the low cleavage efficiency of this specific motif and the incompatible catalytic systems. In this work a highly efficient transformation of β-O-4 lignin major segments into functional quinolines catalyzed by vanadium-based complex and copper has been developed, obtaining a wide range of substituted quinolines with good yields, which is a two-fold increase of quinolines yields when compared with previous sustainable routes. The pathway of this one-pot cascade reaction is investigated and a potential mechanism is proposed, involving the selective aryl ether cleavage, dehydrogenation, aza-Michael addition, dehydration and oxidation process. This work features a highly efficient transformation of lignin β-O-4 segments into N-heterocyclics without additional an oxidant or reductant agent, providing a concise and sustainable route for functional quinolines synthesis.