A simple chlorination pathway to access native-like β-O-4 lignin and monolignols

Description

Abstract

Extracting lignin from lignocellulosic biomass without uncontrolled condensation is challenging due to the formation of recalcitrant C–C bonds during traditional pulping and organosolv fractionation methods, leading to limited valorisation of technical lignins. Emerging “lignin-first” strategies aim to prevent condensation using active stabilization methods but often yield modified protected lignin structures. Here, we report the production of an α-chloro stabilized lignin, both directly from biomass and from acetal-protected lignin, with up to 96% α-chlorination of native α-hydroxy β-aryl ether (β–O–4) linkages. This α-chloro lignin can be converted to a native-like β–O–4 lignin via simple hydrolysis at conditions that are sufficiently mild to largely avoid lignin condensation, yielding up to 63% of the near-theoretical RCF monomer yield on hydrogenolysis. Moreover, we used α-chloro lignin under reductive conditions to produce up to 4.2 wt% of native plant monolignols – Coniferyl and Sinapyl alcohol, effectively reversing lignin biosynthesis.