Direct conversion of lignin to functionalized diaryl ethers via oxidative cross-coupling

Area of Science:

• Biomass valorization
• Organic chemistry
• Sustainable chemistry

Background:

• Lignin is a sustainable source of aromatic compounds.
• Oxidative depolymerization of lignin yields phenolic monomers but suffers from low selectivity due to intermediate instability.
• Repolymerization and dearylation reactions limit product yields in traditional methods.

Purpose of the Study:

• To develop an efficient strategy for extracting aromatic monomers from lignin.
• To overcome the limitations of oxidative depolymerization methods.
• To produce high-value specialty chemicals, specifically functionalized diaryl ethers.

Main Methods:

• Utilizing oxidative cross-coupling reactions.
• Reacting phenylboronic acids with lignin-derived phenolic intermediates.
• Converting reactive phenolic intermediates into stable diaryl ether products.

Main Results:

• Achieved near-theoretical maximum yields of functionalized diaryl ethers (92% for beech lignin, 95% for poplar lignin).
• Suppressed side reactions like repolymerization and dearylation.
• Demonstrated a new pathway for direct lignin transformation.

Conclusions:

• The described strategy offers an efficient method for lignin valorization.
• Functionalized diaryl ethers are produced with high yields and selectivity.
• This approach provides valuable intermediates for pharmaceutical and natural product synthesis.