Synthesis of 2,6-Dimethoxy-p-aminophenol from Hardwood Lignin

Graphical From the hardwood : A route was developed to transform hardwood lignin toward 2,6-dimethoxy- p -aminophenol with high yield and keeping the inherent functional groups. Lignin was first oxidized to syringaldehyde, which was converted toward 2,6-dimethoxy- p -aminophenol via oxidation, oximation, and hydrogenation. The presence of the methoxy group guaranteed the high selectivity. Although the multiple functional groups in biomass offer notable chances for producing high-value chemicals, most of the current studies focused on the (deep) defunctionalization of biomass and its derivates. Herein, we present a catalytic approach to valorize birch wood lignin with maintaining the methoxy and hydroxy groups in the final product (i. e., 2,6-dimethoxy- p -aminophenol), which has applications in different sectors such as pharmaceuticals. The proved approach involves four steps with a high yield (19.8 wt % on the basis of used lignin) to 2,6-dimethoxy- p -aminophenol. The native lignin in birch wood was first converted using alkaline aerobic oxidation in the presence of copper ions toward high-yield syringaldehyde, which was then selectively oxidized toward 2,6-dimethoxy-1,4-benzoquinone using H 2 O 2 and V 2 O 5 . Oximation of 2,6-dimethoxy-1,4-benzoquinone can selectively form 2,6-dimethoxy-1,4-benzoquinone-4-oxime, which can be quantitatively hydrogenated toward 2,6-dimethoxy- p -aminophenol. This work highlights the unique potential of biomass and its derivates for the sustainable production of high-value products with exploring the value of inherent functional groups.