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 language | English |
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Article number | e202410382 |
Journal | Angewandte Chemie - International Edition |
Volume | 63 |
Issue number | 49 |
DOIs | |
Publication status | Published - Dec-2024 |
Keywords
- atom efficient
- cascade reaction
- domino strategy
- lignin valorization
- non-alkylated aromatics