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

Abstract

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 (21.3wt% 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 H2O2 and V2O5. 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.