Elucidating functional group governance for catalytic synthesis of bio-based aromatic amines

Aromatic amines, particularly aniline derivatives, serve as pivotal intermediates in the manufacture of dyes, pharmaceuticals, and polymers. However, their conventional synthesis remains heavily reliant on fossil feedstocks and frequently employs toxic reagents. The valorization of lignin presents a promising, renewable pathway to these valuable compounds, yet the reactivity of lignin-derived phenols varies markedly depending on their functional group substituents. Herein, a pronounced "promotion-inhibition dichotomy" is reported. Alkyl substituents substantially enhance reactivity-achieving a 44.3 mol% yield of aromatic amines from 4-propylphenol, representing a 34.7% increase over phenol. Conversely, methoxy groups exert a strong inhibitory effect in limiting the yield of aromatic amines from 4-propylguaiacol to only 11.0 mol%. Furthermore, Mo-Ga/HZSM-5 catalyst employed under NH 3 -H 2 atmosphere effectively doubled the yield of aromatic amines to 25.9 mol%. A sequential hydrodeoxygenation-amination strategy is further devised, boosting the yield to 34.1 mol%. Notably, by integrating this two-step strategy with a lignin-first biorefining approach, a 16.6 mol% of aromatic amines (based on lignin) could be achieved from birch. This study elucidates key reactivity principles in lignin valorization and demonstrates an integrated strategy that advances the sustainable production of aromatic amines from renewable biomass.