Modified 1,8-Diazabicyclo[5.4.0]undec-7-ene Catalytic System for the Etherification of Lignin-Derived Phenolic Compounds with Green Dimethyl Carbonate

In recent years, lignin and its derivatized phenolic compounds have garnered significant attention in the scientific community due to their sustainability. However, the reaction for converting lignin-based phenolic compounds into other fine chemicals presents several challenges, including stringent reaction conditions, catalyst deactivation, and low reaction efficiency. Herein, an efficient synthesis strategy was proposed for the etherification of lignin-based phenolic compounds with a green methylation reagent of dimethyl carbonate under mild conditions, constructing a chemical barrier wall within the microenvironment of the 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU) catalyst system via inorganic bases to enhance the catalytic activity. Excellent etherification conversion and selectivity of lignin-based ether (>99.5%) was obtained at 145 °C for 60 min. A possible reaction mechanism was also postulated based on the results. This work demonstrates that the construction of barrier walls reduces the loss of active sites of the DBU system, concurrently enhancing the catalytic efficiency, which has a potential application prospect.