The production of 4-ethyltoluene via directional valorization of lignin

4-Ethyltoluene is a very valuable chemical that is currently produced from fossil feedstocks. Production of 4-ethyltoluene from renewable and cheap lignin is of great significance. Herein, we report a new route to produce 4-ethyltoluene from lignin. It was discovered that RhCl3-LiI-LiBF4 was an efficient catalytic system for the reaction of lignin with CO to form 4-ethyltoluene. In the reaction, ethylbenzene was first formed via demethoxylation and depolymerization of lignin, which was further transformed into 4-ethyltoluene by methylation using methoxy from the lignin. The yield of 4-ethyltoluene could reach 9.5 wt% when GVL-lignin was used as the starting material. Interestingly, 5.2 wt% yield of 4-ethyltoluene was obtained when raw poplar was directly used as the starting material. As far as we know, the transformation of lignin with 4-ethyltoluene as the major product has not been reported. This work provides a new strategy to produce valuable aromatic compounds from renewable resources.