Highly Unsaturated Lignin Through Clean and Efficient Ru‐Catalyzed Glycerol Carbonate Allylation and Ring‐Opening Reaction Strategies

Innovative lignin functionalization strategies which graft a large amount of unsaturation onto lignin have been developed. Ruthenium catalysis using allyl alcohol or diallyl ether has been used to develop ready‐to‐graft allylic synthons based on glycerol carbonate and related derivatives. Allylated glycerol carbonate and glycidyl allyl ethers were thus used in effective ring‐opening reactions with high atom economy to convert Kraft, Organosolv, and Soda lignins without prior purification. Glycidyl allyl ethers were grafted onto lignin with a substitution degree of hydroxyl groups up to 90%. Technical and modified lignins were characterized by nuclear magnetic resonance (NMR), infrared (IR), size‐exclusion chromatography (SEC), and thermal properties were determined by differential scanning calorimetry (DSC). The grafting efficiency produces modified lignins with a high level of unsaturation, with thermal properties allowing material shaping, providing new opportunities for material applications.