A strategy for biomass revalorization through Newman-Kwart rearrangement - SRN1 reaction

The valorisation of lignocellulosic biomass is central to the development of sustainable biorefineries, particularly through the upgrading of lignin-derived phenols into high-value products. Sulphur- containing aromatic compounds are important building blocks for materials, pharmaceuticals, and polymer chemistry, yet efficient routes from biomass-derived phenols to thiols and sulphides remain limited. Herein, we demonstrate that the Newman–Kwart rearrangement (NKR), combined with light- promoted SRN1 reactions, provides an effective and versatile strategy for transforming biomass-relevant phenols into sulphur derivatives. A series of O-aryl thiocarbamates were synthesized from model phenols representative of lignin and agricultural residues, followed by their conversion into S-aryl thiocarbamates using complementary NKR methodologies. Mild electrocatalytic and photocatalytic NKR conditions proved particularly effective for electron-rich substrates, while thermal NKR enabled access to electron-poor derivatives, highlighting the complementarity of these approaches. Subsequent base-promoted deprotection and photo-induced SRN1 reactions afforded aryl sulphides without isolation of intermediate thiols. This integrated strategy enables the functionalization of naturally occurring phenols, offering a route to sulphur-containing building blocks for advanced biorefinery applications.