One-Pot Catalytic Cascade for the Depolymerization of the Lignin β-O-4 Motif to Non-phenolic Dealkylated Aromatics

Zhenlei Zhang, Ge Guo, Huaizhou Yang, Lina Csechala, Zhiwen Wang, Clemens Cziegler, Douwe S. Zijlstra, Ciaran W. Lahive, Xiangping Zhang*, Uwe T. Bornscheuer*, Peter J. Deuss*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Aromatic monomers obtained by selective depolymerization of the lignin β-O-4 motif are typically phenolic and contain (oxygenated) alkyl substitutions. This work reveals the potential of a one-pot catalytic lignin β-O-4 depolymerization cascade strategy that yields a uniform set of methoxylated aromatics without alkyl side-chains. This cascade consists of the selective acceptorless dehydrogenation of the γ-hydroxy group, a subsequent retro-aldol reaction that cleaves the Cα−Cβ bond, followed by in situ acceptorless decarbonylation of the formed aldehydes. This three-step cascade reaction, catalyzed by an iridium(I)-BINAP complex, resulted in 75 % selectivity for 1,2-dimethoxybenzene from G-type lignin dimers, alongside syngas (CO : H2≈1.4 : 1). Applying this method to a synthetic G-type polymer, 11 wt % 1,2-dimethoxybenzene was obtained. This versatile compound can be easily transformed into 3,4-dimethoxyphenol, a valuable precursor for pharmaceutical synthesis, through an enzymatic catalytic approach. Moreover, the hydrodeoxygenation potential of 1,2-dimethoxybenzene offers a pathway to produce valuable cyclohexane or benzene derivatives, presenting enticing opportunities for sustainable chemical transformations without the necessity for phenolic mixture upgrading via dealkylation.

Original languageEnglish
Article numbere202410382
JournalAngewandte Chemie - International Edition
Volume63
Issue number49
DOIs
Publication statusPublished - Dec-2024

Keywords

  • atom efficient
  • cascade reaction
  • domino strategy
  • lignin valorization
  • non-alkylated aromatics

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